,,! ,,?\ght ,,is ,,9 ,,! ,,"q ,,! ,,in=mation ,,is ,,9 ,,! ,,answ] ,,hawk9s ,,electrical ,,guide ,,numb] ,,two ,,que/ions ,,answ]s ,,illu/rations ,a ,,progressive ,,c\rse ,,( ,,/udy ,,= ,,eng9e]s1 ,,electricians1 ,,/ud5ts ,,& ,,^? ,,desir+ ,,to ,,acquire ,a ,,work+ ,,k ,,( ,,electricity ,,& ,,its ,,applications ,a ,,practical ,,treatise by ,,hawk9s ,,& ,,/aff ,,!o4 ,,audel ,,co4 #gb ,,fif? ,,ave4 ,,new ,,york4 ,,copyright$1 #aiad1 ,,by ,,!o4 ,,audel ,,co41 ,,new ,,york4 ,pr9t$ 9 ! ,unit$ ,/ates4 ,,table ,,( ,,cont5ts ,,guide ,,no4 #b4 ,,! ,,armature #bba to #bbh ,def9ition--h[ cont9u\s curr5t is obta9$--type ( armature--comp>ison r+ & drum armatures--:y drum armature is ! prevail+ type--disc armatures--:y disc armatures 7 ab&on$4 ,,armature ,,w9d+s #bbi to #bef ,prelim9>y consid]ations--w9d+ diagrams & w9d+ tables--lap & wave w9d+--angul> pit* or spread ( drum coils--p>allel or lap w9d+--s]ies or wave w9d+--d\ble-w9d+s--,siem5s w9d+--objection to ,siem5s w9d+--*ord w9d+--multiplex w9d+s--numb] ( bru%es requir$--numb] ( armature circuits--equaliz] r+s--drum w9d+ requirem5ts4 ,,!ory ,,( ,,! ,,armature #beg to #bhb ,curr5t di/ribution 9 r+ & drum armatures--connection ( bru%es--v>iation ( voltage ar\nd ! commutator--cross magnetization2 field di/ortion--rem$ies = field di/ortion--angle ( lead--demagnetiz+ effect ( armature reaction--effect ( lead--eddy curr5ts2 lam9ation--rem$y = eddy curr5ts--magnetic drag on ! armature--smoo? & slott$ armatures--comp>ison ( smoo? & slott$ armatures--magnetic hy/]esis 9 armature cores--core loss or iron loss--dead turns--friction4 ,,commutation ,,& ,,! ,,commutator #bhc to #cjb ,p]iod ( commutation--commutat+ plane--normal neutral plane--neutral plane--plane ( maximum induction--commutation--position ( ! bru%es--sp>k+--effect ( self-induction--con/ruction ( commutators--po9ts relat+ to commutators--types ( commutator4 ,,bru%es ,,& ,,! ,,bru% ,,ge> #cjc to #cbj ,classification--gauze bru%es--wire bru%es--/rip bru%es--c>bon bru%es--adju/m5t--comp>ison ( copp] & c>bon bru%es--size ( bru%es--numb]--contact angle ( bru%---bru% contact--drop 9 voltage at bru%es--bru% hold]s--bru% rigg+--multipol> bru% ge>4 ,,armature ,,con/ruction #cba to to #cdh ,p>ts--%aft--core--slott$ core--core lam9ations--core bolts--atta*m5t to %aft--insulation ( core discs--tee?--advantages & defects ( slott$ armatures--slott$ cores2 built up con/ruction--v5tilation--insulation ( core--armature w9d+s--con/ruction ( inductors--objection to copp] b>s--v>i\s w9d+s3 h& w9d+--evolute or butt]fly w9d+--connectors--b>rel w9d+--ba/>d w9d+--=m] w9d+--=m] coils--peculi>ity ( evolute coil--/raight out coil--coil reta9+ devices--driv+ horns4 ,,motors #cdi to #chh ,def9ition--pr9ciples--propell+ drag--ess5tial requirem5ts ( con/ruction--! rev]se electromotive =ce--hydraulic analogy--action ( curr5t suppli$ to motor--armature reaction 9 motors--me?od ( />t+ a motor---classes ( motor2 s]ies1 %unt1 & comp\nd--p[] ( a motor--brake horse p[]--mutual relations ( motor torque & spe$--spe$ regulation--s]ies p>allel controll]--int]pole motors4 ,,selection ,,& ,,in/allation #chi to #djf ,g5]al conditions gov]n+ selection--con/ruction--effici5cy--adapt ation ( s]ies & %unt motors--location--f\ndations--erection ( dynamos & motors--connect+ up dynamos--m>9e g5]at+ set--belt clamp--belt lac+--belt spe$--po9ts relat+ to belts--ge> drive--friction drive--electrical connections4 ,,auxili>y ,,app>atus #djg to #dcj ,swit*es--swit* classification & con/ruction--difficulty enc\nt]$ 9 op5+ ! circuit--v>i\s swit*es3 knife1 snap1 & quick break types--fuses--circuit break]s3 maximum1 m9imum1 rev]se curr5t1 maximum & rev]se curr5t1 no voltage break]--discrim9at+ cut out--"t limit atta*m5ts--rheo/ats--/>t+ boxes--swit*bo>ds4 ,,*apt] ,,xvii ,,! ,,armature ,! armature ( a dynamo consi/s ( coils ( insulat$ wire w\nd ar\nd an iron core1 & s arrang$ t electric curr5ts are induc$ 9 ! wire :5 ! armature is rotat$ 9 a magnetic field or ! field magnets rotat$ & armature held /ation>y4 ,! commutator is 9 fact a "p ( ! armature1 b is ( suffici5t importance to be consid]$ 9 a sep>ate *apt]4 ,ques4 ,:at are ! practical objections to ! elem5t>y armature1 describ$ 9 fig4 #afe8 ,ans4 ,x induces a v feeble curr5t1 :i* is n ( con/ant pressure1 b pulsat+2 t is1 x consi/s ( two pron\nc$ impulses 9 ea* revolution z %[n 9 fig4 #afh4 ,ques4 ,:y does ! elem5t>y armature produce a pulsat+ curr5t8 ,ans4 ,! pulsations are due to ! coil mov+ alt]nately into1 & out (1 ! positions ( be/ & lea/ action 9 ! magnetic field4 ,ques4 ,h[ is a cont9u\s curr5t1 or "o ( uni=m pressure obta9$8 ,ans4 ,if an additional coil be add$ to ! elem5t>y armature1 at "r angles to ! exi/+ coil1 & its ends suitably connect$ to a f\r "p commutator1 z 9 fig4 #ahe1 s t "o coil is 9 ! position ( be/ action1 :ile ! o!r is 9 ! position ( lea/ action1 ! pulsations ( ! result+ curr5t w be ( less magnitude4 ,by increas+ ! coils & suitably alt]+ ! con/ruction ( ! commutator to accommodate ! ends ( ^! coils1 ! resultant curr5t may be repres5t$ by practically a /raight l9e1 indicat+ ! s call$ cont9u\s curr5t1 in/ead ( ! wavy resultant curve ,no4 #f1 z illu/rat$ 9 fig4 #ahg4 ,illu/ration3 ,,fig #bdg4--,r+ armature ( f\r pole dynamo3 diagram ( w9d+ & connections1 %[+ direction ( ! induc$ curr5ts4 ,! curr5ts 9 ! w9d+s "u ! upp] ,n & ,s poles are oppos$ to ea* o!r & fl[ to ! ext]nal circuit by ! positive bru% #a1 & back to ?is half ( ! armature by ! negative bru%es #c & #d4 ,at ! same in/ant ! oppos$ curr5ts 9 ! l[] w9d+s fl[ to ! ext]nal circuit by positive bru% #b & return to ! armature ?r\gh negative bru%es #c & #d4 ,! armature is ?us divid$ into f\r circuits & f\r bru%es are requir$ :i* mu/ be plac$ betwe5 ! poles s z to %ort circuit ! coils z !y pass ?r\gh ! neutral space4 ,9 ?is =m ( w9d+ !re is no diff]5ce ( pot5tial betwe5 ! bru%es1 s t !y are connect$ 9 p>allel1 z are also ! negative bru%es1 & !n to ! ext]nal circuit4 ,9 multipol> ma*9es !re are z _m bru%es z pole pieces4 ,s9ce opposite commutator b>s are ( ! same pot5tial on ?is f\r pole dynamo !y may be jo9$ by a cross connect+ wire & two bru%es1 z #b & #d1 disp5s$ )4 ,?is c only be done :5 !re is an ev5 numb] ( coils4 ,! armature is said to be cross connect$4 ,an armature = practical use has a l>ge numb] ( coils1 suitably arrang$ ^u an iron core1 s t a l>ge proportion ( !m are always actively cutt+ ! l9es ( =ce1 or mov+ into ! positions ( be/ action 9 ! magnetic field4 ,types ( ,armature4--,al?\gh !re are _m =ms ( armature1 all may be divid$ into ?ree classes1 accord+ to ! arrangem5t ( ! coils or w9d+ on ! core1 z3 #a4 ,r+ armatures2 #b4 ,drum armatures2 #c4 ,disc armatures4 ,ea* ( ^! =ms ( armature has its own special advantages = p>ticul> purposes1 ! disc type be+ lea/ 9 favor & n hav+ _h any ext5sive application 9 ?is c\ntry4 ,illu/ration3 ,,fig4 #bdh4--;,e>ly =m ( ,gramme r+ armature1 ! core be+ %[n cut ?r\gh1 & "s ( ! coils displac$ to make x cle>]4 ,! core1 ,f1 consi/s ( a quantity ( iron wire w\nd cont9u\sly to =m a r+ ( ! %ape %[n by ! section4 ,ov] ?is is w\nd ab\t ?irty coils ( insulat$ copp] wire1 ,b ,c ,d1 etc41 ! direction ( ! w9d+ ( ea* be+ ! same1 & _! adjac5t ends connect$ toge!r4 ,! commutator segm5ts consi/ ( a correspond+ numb] ( brass angle pieces1 m1 n1 :i* are fix$ aga9/ ! wood5 boss1 o1 c>ri$ on ! driv+ %aft4 ,! junction ( e two adjac5t coils is connect$ to "o ( ! commutator segm5ts1 z %[n at n4 ,ques4 ,:at is ! comp>ison betwe5 r+ & drum armatures8 ,ans4 ,! drum armature is electrically & me*anically ! m effici5t1 possess+1 z x does1 possibilities 9 ! way ( bett] me*anical con/ruction ( ! core1 & 9 ! arrangem5t & fix+ ( ! inductors !reon n to be f\nd 9 ! r+ =m4 ,less wire & magnetiz+ curr5t are requir$ = ! field magnets = a giv5 output ?an ) ! r+ armature4 ,drum w9d+ is n s simple z r+ w9d+1 & x is m difficult to v5tilate a drum ?an a r+ armature1 x be+ necess>y to provide special v5tilat+ ducts4 ,illu/ration3 ,,fig4 #bdi4--,mod]n =m ( ,gramme r+ armature4 ,! core consi/s ( a numb] ( ?9 flat r+s ( well anneal$ *>coal iron1 ! out] diamet] ( ea* r+ or disc be+ #aa in*es1 & its inn] diamet] #i in*es4 ,%eets ( ?9 pap] insulate ea* disc f its neighbors to prev5t ! fl[ ( eddy curr5ts4 ,! armature is m\nt$ on a /eel %aft to :i* is key$ a f\r arm$ metal spid]1 ! extremities ( ^: arms fit into not*es cut 9 ! inn] edges ( ! s(t iron core r+s1 s t a good me*anical connection is obta9$ betwe5 ! core & ! %aft4 ,! spid] is made ( a non-magnetic metal1 to r$uce ! t5d5cy to leakage ( l9es ( =ce across ! int]ior ( ! armature4 ,! armature inductors consi/ ( cotton cov]$ copp] wire ( ,no4 #i /&>d wire gauge1 w\nd ar\nd ! core 9 "o lay]1 & (f]+ a resi/ance1 f bru% to bru%1 ( #j4jdh ohm4 ,!re are two convolutions 9 ea* section1 ! adjac5t ends ( neighbor+ sections be+ sold]$ to radial lugs project+ f ! commutator b>s4 ,ques4 ,describe a r+ armature4 ,ans4 ,x consi/s ess5tially ( an iron r+1 ar\nd :i* is w\nd a numb] ( coils4 ,^! v>i\s coils are w\nd on sep>ately1 ! wire be+ c>ri$ ov] ! outside ( ! r+1 !n ?r\gh ! c5t] op5+ & aga9 ar\nd ! outside1 ?is op]ation be+ repeat$ until ! w9d+ = t individual section is complet$4 ,! adjac5t coil is !n w\nd 9 ! same way1 ! ends ( ea* be+ br\ght out to ! commutator side ( ! armature1 ! arrangem5t ( ! coils on ! r+ & connections ) ! commutator be+ %[n 9 fig4 #bdg1 examples ( actual con/ruction be+ %[n 9 figs4 #bdh & #bdi4 ,ques4 ,= :at conditions ( op]ation is ! r+ armature specially adapt$1 & :y8 ,ans4 ,x is well suit$ to ! g5]ation ( small curr5ts at high voltage1 z = s]ies arc light+1 because ! num]\s coils c be v well insulat$4 ,illu/ration3 ,,fig4 #bej4--;,di/ribution ( magnetic l9es ( =ce ?r\gh a ,gramme r+4 ,s9ce ! metal ( ! r+ furni%es a pa? ( lea/ reluctance1 mo/ ( ! magnetic l9es w foll[ ! metal ( ! r+ & v few w p5etrate into ! ap]ture ( ! int]ior4 ,?is condition causes a s]i\s defect 9 ! action ( r+ armatures r5d]+ ! w9d+ ar\nd ! int]ior useless = ! production ( electromotive =ce4 ,h5ce1 9 r+ armatures only ab\t half ( ! w9d+ is effective1 ! re/ or dead wire1 add+ its resi/ance to ! circuit1 ?us decreas+ ! effici5cy ( ! ma*9e4 ,ques4 ,:y does a r+ armature require m copp] 9 ! w9d+ ?an a drum armature8 ,ans4 ,= ! reason t ^? inductors :i* lie on ! inn] side ( ! iron r+1 be+ scre5$ f practically all ! l9es ( =ce1 z %[n 9 fig4 #bej1 d n g5]ate any curr5t4 ,num]\s attempts h be5 made to utilize ?is "p ( ! w9d+ by mak+ ! pole pieces ext5d ar\nd ! r+ 9 su* a mann] t l9es ( =ce w pass to ! inside ( ! r+1 also by arrang+ an additional pole piece on ! inside ( ! armature1 b me*anical consid]ations h %[n ^! me?ods to be impractical4 ,ques4 ,is any portion ( ! w9d+ ( a drum armature inactive8 ,ans4 ,yes2 ! end connectors d n g5]ate any curr5t4 ,illu/ration3 ,,fig4 #bea4--;,illu/rat+ ! pr9ciple ( ,siem5s' drum w9d+4 ,9 ord] to make ! w9d+ & connections cle>1 "o coil & ! commutator is %[n assembl$1 al?\gh ! latt] is n put 9 place until aft] all ! sections h be5 w\nd1 ! ends ( ! wires be+ tempor>ily twi/$ toge!r until all c be sold]$ to ! ris]s4 ,! cores ( ^! e>ly ma*9es 7 ( wood ov]spun circumf]5tially ) iron wire be=e receiv+ ! longitud9al copp] w9d+s4 ,ques4 ,:at is ! *ief advantage ( ! drum armature8 ,ans4 ,x r$uces consid]ably ! l>ge am\nt ( dead wire necess>y ) ! r+ type4 ,ques4 ,h[ is ?is accompli%$8 ,ans4 ,by w9d+ ! wire entirely on ! out] surface ( a cyl9d] or drum1 z x is call$1 z %[n 9 fig4 #bea1 ?us none ( ! wire is scre5$ by ! metal ( ! core4 ,illu/ration3 ,,fig4 #beb4--;,elem5t>y f\r coil drum w9d+1 %[+ ! connections ) ! commutator segm5ts1 & directions ( curr5ts 9 ! sev]al coils4 ,! action ( ?is type ( armature is fully expla9$ 9 ! text4 ,fig4 #beb %[s an elem5t>y f\r coil drum armature4 ,/>t+ f ! po9t a & foll[+ ! w9d+ ar\nd )\t ref]5ce at fir/ to ! commutator1 x w be f\nd t ! rectangul> turns ( ! wire =m a clos$ circuit1 & are electrically 9 s]ies ) "o ano!r 9 ! ord] ( ! numb]s m>k$ on !m4 ,) respect to ! connections to ! f\r segm5ts w1 x1 y1 z1 ( ! commutator x w be f\nd t at two ( ^!1 x & y1 ! pressures 9 ! w9d+s are bo? direct$ f1 or bo? direct$ t[>d ! junction ) ! connect+ wire4 ,at ! o!r two segm5ts1 z & w1 "o pressure is t[>d ! junction & ! o!r direct$ f x4 ,if1 !re=e1 ! bru%es be plac$ on x & y !y w supply curr5t to an ext]nal circuit1 z & w1 = ! mom5t be+ idle segm5ts4 ,disc ,armatures4--,! inductors ( a disc armature move 9 a plane1 p]p5dicul> to ! direction ( ! l9es ( =ce1 ab\t an axis p>allel to !m z %[n 9 fig4 #bec4 ,! ma9 difficulty ) ?is type has be5 9 con/ruct+ x s t x w be /rong & capable ( resi/+ we> & te>4 ,x 0 introduc$ 9 an ef=t to avoid ! losses due to eddy curr5ts & hy/]esis pres5t 9 ! o!r types ( armature4 ,illu/ration3 ,,fig4 #bec4--;,disc armature ( ,niaudet4 ,x is equival5t to a r+ armature1 hav+ ! coils turn$ ?r\gh an angle ( #ij1 s t all ! coils lie 9 a plane p]p5dicul> to ! axis ( rotation4 ,! connections ( ! coils ) ea* o!r & ) ! commutator rema9 ! same1 ! beg9n+ & ! end ( adjac5t coils lead+ to a common commutator b> z %[n4 ,! magnetic field is arrang$ by ! use ( two magnets1 s arrang$ z to pres5t ! nor? pole ( "o to ! s\? pole ( ! o!r1 & vice v]sa4 ,9 ! figure "o ( ^! magnets is consid]$ z above ! pap]1 & ! o!r bel[4 ,if ?is armature be rotat$ ?r\gh ! magnetic field z %[n1 a rev]sal ( curr5t takes place 9 ea* coil1 :5 x is 9 su* a position t "o ( its diamet]s co9cides ) ! pole l9e1 ,,ns4 ,if ! bru%es be set s z to %ort circuit ! coils t are 9 ?is position1 ! armature w be divid$ into two bran*+s1 ! curr5t fl[+ 9 an opposite direction 9 ea*1 & a direct curr5t w fl[ 9 ! ext]ior circuit4 ,on acc\nt ( ! nature ( ! con/ruction ( a disc armature1 x is necess>y t ! coils subject to induction occupy z small a space z possible 9 ! direction ( _! axes4 ,?is requirem5t1 z well z ! connection ( ! inductors ) ea* o!r & ) ! commutator1 prev5t$ ! g5]al adoption ( ?is =m ( armature1 & subsequ5t exp]i5ce fail$ to ju/ify ! exi/5ce ( ! type4 ,,*apt] ,,xviii ,,armature ,,w9d+s ,to connect up rightly ! inductors on an armature s z to produce a desir$ result is a simple matt] 9 ! case ( r+ w9d+1 = bipol> or multipol> ma*9es4 ,x is a less easy matt] 9 ! case ( drum w9d+1 especially = multipol> ma*9es4 ,(t5 !re are sev]al diff]5t ways ( arriv+ at ! same result1 & ! fact t me?ods :i* are electrically equival5t may be geometrically & me*anically diff]5t makes x desirable to h a sy/ematic me?od ( treat+ ! subject4 ,! elem5t>y arrangem5t ( drum & disc armatures has already be5 consid]$1 :i* is suffici5t explanation = small armature coils ( only a few turns ( wire1 b 9 ! case ( l>g] ma*9es :i* require _m coils1 fur!r treatm5t ( ! subject is necess>y4 ,= example1 9 ord] to direct ! w9d] h[ to make ! connections =1 say a f\r pole ma*9e hav+ #ajj b>s spac$ ar\nd its armature1 "s pla9 me?od ( repres5t+ all ! connections s t !y may be easily und]/ood is necess>y4 ,f ?is ! workman f9ds out :e!r he is to connect ! front,a end ( b> ,no4 #a across to #ej or across a qu>t] ( ! circumf]5ce to #bd1 or across ?ree qu>t]s ( x to b> #ge4 ,aga91 he asc]ta9s to :i* b> he is to connect ! back#a end ( ! b>1 & h[ ! b>s are to be connect$ to ! commutator4 #a ,,note3--,! front end means ! end at :i* ! commutator is locat$4 ,armatures are mo/ conv5i5tly reg>d$ f ?is end1 ! opposite end be+ kn[n z ! back end4 ,w9d+ ,diagrams & ,w9d+ ,tables4--,9 ! con/ruction ( armatures1 in/ructions to w9d]s are giv5 9 ! =m ( diagrams & tables4 ,9 ! tables ! lett]s ,f & ,b /& = front & back1 mean+ t[>d ! front end1 & f ! front end respectively4 ,! lett]s ,u & ,d /& = up & d[n4 ,illu/ration3 ,,fig4 #bed4--;,end ( r+ w9d+ = a f\r pole ma*9e4 ,an end view is simply a view %[+ ! arrangem5t ( ! armature inductors & connections look+ f ! front or commutator end4 ,a develop$ view ( ! above w9d+ is %[n 9 fig4 #beg4 ,!re are ?ree k9ds ( w9d+ diagram3 #a4 ,end view diagram2 #b4 ,radial diagram2 #c4 ,develop$ diagram4 ,! end view is simply a view %[+ ! arrangem5t ( ! armature inductors & connections look+ f ! front or commutator end1 su* z %[n 9 fig4 #bed4 ,9 ! radial diagram ! inductors ( ! armature are repres5t$ by %ort radial l9es1 :ile ! end connectors are repres5t$ by curves or zigzags1 ^? at "o end ( ! armature be+ drawn )91 ^? at ! o!r end1 )\t ! circumf]5ce ( ! armature4 ,) ! radial diagram x is easi] to foll[ ! circuits & to di/+ui% ! back & front pit* ( ! w9d+4 ,illu/ration3 ,,fig4 #bee4--,p>tial sket* ( a f\r pole ma*9e laid on its side4 ,if ! obs]v] imag9e himself plac$ at ! c5t]1 & ! panorama ( ! f\r poles to be !n laid out flat1 ! develop$ view ?us obta9$ w\ld appe> z 9 fig4 #bef4 ,! develop$ diagram is a mode ( repres5tation1 orig9ally sugge/$ by ,frits*e ( ,b]l91 9 :i* ! armature w9d+ is consid]$ z ?\gh ! entire /ructure _h be5 develop$ out ( a flat surface4 ,?is is be/ expla9$ by aid ( figs4 #bee & #bef4 ,if 9 fig4 #bee1 :i* repres5ts an armature core & a f\r pole field1 wires a & c be plac$ p>allel to ! axis ( ! armature to repres5t two ( ! armature inductors1 & mov$ along ! air gap space clockwise pa/ ! ,s poles1 !y w cut magnetic l9es induc+ electromotive =ces 9 ! directions indicat$4 ,to attempt to %[ a l>ge numb] ( inductors 9 a draw+ ( ?is k9d w\ld be un9telligible4 ,accord+ly1 ! obs]v] is consid]$ z be+ plac$ at ! c5t] ( ! armature1 & ! panorama ( ! f\r poles surr\nd+ him to be !n laid out flat or develop$ z 9 fig4 #bef4 ,! faces ( ! ,n & ,s poles are %ad$ obliquely = di/9ction4 ,by *oos+ ! prop] directions = ^! oblique l9es1 a piece ( pap] hav+ a n>r[ slit to repres5t ! wire may be laid ov] ! draw+ ( ! pole & :5 mov$1 z indicat$ by ! dott$ arr[s to ! "r1 ! slit 9 pass+ ov] ! oblique l9es w cause an app>5t motion 9 ! direction 9 :i* ! curr5t 9 reality t5ds to fl[4 ,x is easily rememb]$ :i* way ! oblique l9es mu/ slope1 = ^? on ! ,n pole slope p>allel to ! oblique "p ( ! lett] ,n4 ,lap ,w9d+ & ,wave ,w9d+4--,9 w9d+ armatures !re are two di/9ct me?ods employ$1 kn[n respectively z lap & wave w9d+4 ,! di/9ction arises 9 ! foll[+ mann]3 ,s9ce ! inductors1 9 pass+ a nor? pole g5]ate electromotive =ces 9 "o direction1 & 9 pass+ a s\? pole g5]ate electromotive =ces 9 ! opposite direction1 x is evid5t t an inductor 9 "o ( ^! gr\ps ought to be connect$ to "o 9 ne>ly a correspond+ position 9 ! o!r gr\p1 s t ! curr5t may fl[ d[n "o & up ! o!r 9 agreem5t ) ! directions ( ! electromotive =ces4 ,! ord] foll[$ 9 mak+ ^! connections gives rise to lap & wave w9d+s4 ,illu/ration3 ,,fig4 #bef4--;,develop$ view ( ! f\r pole field %[n 9 p]spective 9 fig4 #bee4 ,ques4 ,:at is lap w9d+8 ,ans4 ,"o 9 :i* ! ends ( ! coils come back to adjac5t segm5ts ( ! commutator2 ! coils ( su* a w9d+ lap ov] ea* o!r4 ,ques4 ,:at is a wave w9d+8 ,ans4 ,"o 9 :i* ! coil ends div]ge & g to segm5ts widely sep>at$1 ! w9d+ to a c]ta9 ext5t resembl+ a wave4 ,illu/ration3 ,,fig4 #beg4--;,developm5t ( r+ w9d+ ( f\r pole ma*9e %[n 9 fig4 #bed4 ,! dead wire or inactive inductors on ! inside ( ! r+ are %[n 9 dott$ l9es1 ! full l9es repres5t+ ! active portion ( ! w9d+4 ,angul> ,pit* or ,spread ( ,drum ,coils4--,be=e tak+ up ! w9d+ z a :ole1 ! =m ( ! individual coil %\ld be consid]$4 ,fig4 #bfj %[s an end view ( "o coil 9 position on a drum armature ( a multipol> ma*9e4 ,! two slots ,x & ,y conta9 ! sides ( ! coil & ! di/ance betwe5 !m on ! surface ( ! drum is call$ ! angul> pit* or spread ( ! coil4 ,!oretically ?is is equal to ! pit* ( ! poles1 repres5t$ by ! angle ,m1 :i* is ! angle betwe5 ! pole c5tres4 ,illu/ration3 ,,figs4 #beh & #bei4--,wood5 armature core & w9d+ table = practice 9 armature w9d+4 ,by us+ /r+s ( diff]5t colors to repres5t ! v>i\s coils1 ! pa? ( ea* coil is easily trac$ :5 ! w9d+ is complet$1 z 9 fig4 #bfc4 ,= in/ance1 on a f\r pole ma*9e ! pit* w\ld be #ij1 on a six pole ma*9e1 #fj1 etc4 ,usually ! angul> pit* ( ! coil is made j a little less ?an ! pole pit* ( ! ma*9e1 9 ord] to %ort5 ! end connections ( ! coils f slot to slot4 ,h[ev]1 if ! angul> pit* be made too small tr\ble w be enc\nt]$ 9 commutation4 ,9 addition to ! angul> pit* !re is ! commutator pit* :i* relates to ! di/ance ar\nd ! commutator bridg$ by ! ends ( ! coil4 ,?us1 if ! commutator segm5ts 7 numb]$ consecutively #a1 #b1 #c1 etc41 & ! commutator pit* say is #aj1 x w\ld signify t "o end ( ! coil 0 connect$ to segm5t #a & ! o!r end to segm5t #aa2 ! ends ( ! next coil 9 ord] !n w\ld be connect$ to segm5ts #b & #ab1 9 ea* case !re w\ld be t5 segm5ts betwe5 ! two segm5ts connect+ ) ! coil ends4 ,illu/ration3 ,,fig4 #bfj4--;,end view ( drum armature ( a multipol> ma*9e %[+ "o coil 9 position to illu/rate ! angul> pit* or spread ( drum coils4 ,p>allel or ,lap ,drum ,w9d+4--,9 ord] to avoid mu* ( ! difficulty usually exp]i5c$ by /ud5ts ( drum w9d+1 ! beg9n] %\ld con/ruct = himself a wood5 armature core ^u :i* he c w9d /r+s ( v>i\s colors1 or wires ) di/9ctive insulation1 to repres5t ! num]\s coils t are us$ on real armatures4 ,a few w9d+s attempt$ 9 ?is way w make cle> _m po9ts t _c be s easily grasp$ f a writt5 description4 ,! type ( drum core be/ adapt$ = ?is "w is ! slott$ v>iety z %[n 9 fig4 #beh1 z x w facilitate ! w9d+4 ,! core z %[n 9 ! illu/ration has twelve slots & six commutator segm5ts1 ! numb] ( ea* requir$ = ! example ( lap w9d+ indicat$ 9 ! w9d+ table fig4 #bei4 ,9 mak+ ! wood5 core1 ! slots may be =m$ by nail+ a s]ies ( ?9 /rips ar\nd a cyl9drical piece ( wood1 ?us avoid+ ! tr\ble ( cutt+ grooves4 ,9 ! illu/rations ! commutator segm5ts are %ort5$ 7leav+ no room = bru%es7 9 ord] to %[ ! connections z cle>ly z possible4 ,illu/ration3 ,,fig4 #bfa4--;,develop$ view ( a typical lap w9d+4 ,f ! figure x is se5 t at ! back ( ! armature ea* inductor is unit$ to "o five places fur!r on1 t is1 #a to #f1 #c to #h1 etc41 & at ! front end ( ! w9d+1 aft] hav+ made "o elem5t1 z = example d-#g-ab-;e1 !n =ms a second elem5t e-#i-ad-;f :i* laps ov] ! fir/1 & s on all ar\nd until ! w9d+ returns on itself4 ,ques4 ,describe ! simple lap w9d+ fig4 #bei4 ,ans4 ,z giv5 9 ! table1 x consi/s ( six loops ( wire pres5t+ twelve inductors on ! cyl9drical surface ( ! core or drum4 ,9 ! table1 six wires are %[n1 hav+ di/9ctive & v>i$ insulation s z to readily di/+ui% ! diff]5t coils4 ,opposite ^! are lett]s & figures designat+ ! pa? & connections ( ea* coil4 ,ques4 ,:at is ! pa? ( ! fir/ coil8 ,ans4 ,accord+ to ! table x is3 ,a -- #a -- #f -- ,b t is1 "o end ( ! wire is connect$ to commutator segm5t ,a 7fig4 #bfb7 & !n w\nd to ! back ( ! drum ?r\gh slot #a1 across ! back ( ! drum to slot #f1 return+ ?r\gh ?is slot1 & !n connect$ ) commutator segm5t ,b4 ,illu/ration3 ,,fig4 #bfb4--,skeleton view ( wood5 armature core %[+ 9 position ! fir/ two coils ( ! w9d+ indicat$ 9 ! table fig4 #bei4 ,ques4 ,describe ! pa? ( ! second coil4 ,ans4 ,! second coil1 hav+ ! block insulation1 is w\nd accord+ to ! table1 9 ! ord]3 ,b--#c--h--;,c t is1 beg9n+ at segm5t ,b1 !nce to back ( drum ?r\gh slot #c1 across ! back to slot #h1 return+ ?r\gh ?is slot & end+ at segm5t ,c4 ,! complet$ w9d+ ( ! fir/ two coils are %[n 9 fig4 #bfb1 ! drum be+ %[n 9 dott$ l9es s t all ( ea* coil may be visible4 ,illu/ration3 ,,fig4 #bfc4--,view ( complet$ w9d+ z indicat$ 9 ! table fig4 #bei4 ,?us ! pa? ( ! fir/ coil1 accord+ to ! table is ,a-#a-f-;,b :i* means t ! coil beg9s at segm5t ,a ( ! commutator1 rises to slot #a1 & proce$s ?r\gh ! slot to ! back ( ! drum2 !nce across ! back to slot #f1 ?r\gh ! slot & end+ at segm5t ,b4 ,! o!r coils are w\nd 9 simil> ord] z indicat$ 9 ! table4 ,ques4 ,h[ are ! rema9+ coils w\nd on ! drum8 ,ans4 ,ea* ( ! succe$+ coils are w\nd z indicat$ 9 ! table1 ! la/ connection be+ made to segm5t ,a1 ! "o f :i* ! w9d+ />t$4 ,ques4 ,:at is ! g5]al =m ( ! complet$ w9d+8 ,ans4 ,x may be consid]$ simply z a wire w\nd spirally ar\nd ! drum1 ) loops br\ght d[n to ! commutator segm5ts1 & end+ at ! segm5t f :i* ! />t 0 made4 ,! complet$ w9d+ z indicat$ by ! table is %[n 9 fig4 #bfc4 ,"h ! pa? ( ea* coil is easily di/+ui%$ by means ( ! v>i$ insulations al?\gh 9 "p hidd5 by ! drum4 ,fig4 #bfd %[s a develop$ view ( ! w9d+4 ,illu/ration3 ,,fig4 #bfd4--;,develop$ view ( ! w9d+ %[n 9 p]spective 9 fig4 #bfc4 ,ques4 ,:at condition mu/ obta9 9 w9d+ an ev5 numb] ( coils8 ,ans4 ,! wire mu/ n be w\nd ar\nd ! drum to diametrically opposite positions1 z = in/ance #a to #g 9 fig4 #bfe4 ,ques4 ,:y is ?is8 ,ans4 ,! reason w be cle>ly se5 by attempt+ ! w9d+ on ! wood5 core4 ,a w9d+ ( ?is k9d on ! drum fig4 #beh1 w\ld proce$ z foll[s3 ,a--#a-- #g--;,b ,b--#c-- #i--;,c ,c--#e--aa--;,d ,9 ord] n[ to cont9ue w9d+ 9 a regul> way1 ! wire f segm5t d %\ld pass to ! re> ( ! armature along space #g1 b ?is space is already occupi$ by ! return ( ! fir/ coil4 ,cont9u+ ! w9d+ f ?is po9t1 x w\ld be necess>y to c>ry ! wire f segm5t d to #f or #h1 result+ 9 an unbalanc$ w9d+4 ,illu/ration3 ,,fig4 #bfe4--,lap w9d+ = bipol> ma*9e1 ) unev5 numb] ( coils2 9 ?is case ! re> connectors may be made directly across a diamet] z %[n4 ,ques4 ,h[ is a symmetrical w9d+ obta9$ hav+ an ev5 numb] ( coils8 ,ans4 ,! inductors1 9 pass+ f ! front to ! re> ( ! armature1 fig4 #bfc1 mu/ occupy positions #a1 #c1 #e1 #g1 #i1 #aa1 & ! ev5 numb]$ positions w !n s]ve z ! returns = ^! wires4 ,9 ! example "h %[n !re are six coils1 compris+ twelve inductors & six commutator segm5ts2 x %\ld be not$1 h[ev]1 t if !re 7 an unev5 numb] ( coils1 ! re> connections c\ld be made directly across a diamet] z %[n 9 fig4 #bfe1 :i* w\ld give a symmetrical w9d+4 ,) t5 slots z %[n 9 ! figure1 ! drum w\ld be w\nd1 = a bipol> ma*9e1 accord+ to ! foll[+ table3 ,a--#a-- #f--;,b ,b--#c-- #h--;,c ,c--#e--aj--;,d ,d--#g-- #b--;,e ,e--#i-- #d--;,f ,illu/ration3 ,,fig4 #bff4--;,develop$ view ( a typical wave w9d+4 ,?is w9d+1 in/ead ( lapp+ back t[>d ! commutator segm5t f :5ce x came1 z 9 lap w9d+1 turns ! o!r way4 ,= in/ance1 d-#g-ab does n return directly to e1 b goes on to i1 :5ce ano!r elem5t i-#ag-d-;e cont9ues 9 a sort ( zigzag wave4 ,ques4 ,are coils su* z %[n 9 figs4 #bfc & #bfe us$ 9 practice8 ,ans4 ,no1 = practical use ea* coil w\ld consi/ ( sev]al turns1 ! diagram !n m]ely indicates ! end connections & slots = ! sev]al turns ( ea* coil4 ,s]ies or ,wave ,drum ,w9d+4--,9 ?is mode ( w9d+1 ! inductors are arrang$ ar\nd ! armature s t !y d n turn back1 ?us describ+ a zigzag or wave-l pa?2 t is1 ! coil ends in/ead ( connect+ ) adjac5t segm5ts ( ! commutator1 are atta*$ to segm5ts m or less remote4 ,ques4 ,describe ! circuits ( a simple or simplex wave w9d+4 ,ans4 ,only two sets ( bru%es are requir$ = su* a w9d+1 b z _m bru%es z !re are poles c be us$4 ,illu/ration3 ,,fig4 #bfg4--;,five coil wave w9d+ = a f\r pole ma*9e4 ,9 ?is w9d+ only two bru%es are us$1 !re be+ only two pa?s ?r\gh ! armature4 ,ques4 ,= :at s]vice are wave w9d+s adapt$8 ,ans4 ,!y are g5]ally us$ on armatures design$ to furni% a curr5t ( high voltage & l[ amp]age4 ,an example ( wave drum w9d+ = a f\r pole ma*9e is %[n 9 fig4 #bfg4 ,= simplicity1 v few coils are tak51 !re be+ only five z %[n 9 ! illu/ration4 ,to make ! w9d+1 "o /rip %\ld be remov$ f ! wood5 core & ! o!rs spac$ equally ar\nd ! cyl9drical surface4 ,?is w give t5 slots1 ! numb] requir$ = ! five coils4 ,! w9d+ is indicat$ 9 ! foll[+ table3 ,a--#a-- #d--;,c ,b--#c-- #f--;,d ,c--#e-- #h--;,e ,d--#g--aj--;,a ,e--#i-- #b--;,b ,accord+ly ! fir/ coil />t+ at segm5t ,a1 is c>ri$ to ! back ( ! drum ?r\gh slot #a1 !nce across ! back & return+ ?r\gh slot #d1 end+ at segm5t ,c ! />t+ po9t ( ! second coil4 ,ea* coil is w\nd on 9 simil> mann]1 ! la/ coil end+ at segm5t ,a1 ! />t+ po9t ( ! fir/ coil4 ,a develop$ view ( ! w9d+ is %[n 9 fig4 #bfh4 ,d\ble ,w9d+s4--,9 ! v>i\s drum w9d+s ?us f> consid]$1 ea* coil _h its individual slots1 t is1 no two occupi$ ! same two slots4 ,?is arrangem5t gave twice ! numb] ( slots z commutator segm5ts4 ,illu/ration3 ,,fig4 #bfh4--;,develop$ view ( ! five coil wave w9d+ %[n 9 fig4 #bfg4 ,9 a d\ble w9d+ !re are z _m segm5ts z slots1 ea* ( ! latt] conta9+ two inductors1 compris+ "p ( two coils4 ,! ,siem5s ,w9d+4--,9 w9d+ drum armatures = bipol> dynamos ( two horse p[] or less1 & especially = v small ma*9es z us$ 9 fan or sew+ ma*9e motors1 a =m ( w9d+1 kn[n z ! ,siem5s w9d+1 :i* is %[n 9 fig4 #bga1 is l>gely us$4 ,x consi/s 9 divid+ ! surface ( ! armature core 9 "o equal numb] ( slots1 say #af1 & us+ a #af "p commutator4 ,9 ! ,siem5s w9d+1 ! end ( ! wire us$ at ! />t is to be connect$ to ! fir/ commutator b>1 b mu/ be fa/5$ to ! armature core out ( ! way s z n to int]f]e ) ! w9d+ ( ! coils4 ,if eight turns ( wire be requir$ to fill a slot ) "o lay]1 !n ! wire is c>ri$ f front to back & b5t aside s z to cle> ! %aft2 aft] pass+ across ! back or pulley end ( ! armature1 x is w\nd 9 ! diametrically opposite section & br\ght to ! front1 !n across ! commutator end & up close to ! beg9n+ ( ! coil4 ,illu/ration3 ,,fig4 #bfi4--,s]ies connect$ wave w\nd r+ armature = a f\r pole ma*9e4 ,! coils are s connect$ t only two bru%es are necess>y4 ,s9ce eight turns are to be us$1 ! process ( w9d+ is cont9u$ until ! section is full & ! end ( ! coil w lie 9 a position ready to beg9 ! next section4 ,sometimes ! wire is cut at ?is "p ( ! coil leav+ #c or #d in*es project+ = connect+ to ! commutator b> #b1 or next to ! fir/ b> :]e ! w9d+ 0 />t$4 ,! usual practice is1 h[ev]1 to make a loop ( ! wire ( suffici5t l5g? to make ! connection to ! commutator & x has ! advantage t s9ce all ( ! coils on ! armature are jo9$ 9 s]ies1 ! end+ ( "o coil is jo9$ to ! beg9n+ ( ! next :i* avoids mak+ mi/akes 9 mak+ ! commutator connections4 ,if ! ends be cut !y %\ld be m>k$ beg9n+ & end to avoid tr\ble1 because if !y get mix$1 x w be necess>y to te/ ea* coil ) a batt]y & compass ne$le 9 ord] to det]m9e ! pol>ity produc$ & f9d :i* is ! beg9n+ ( ! coil & :i* ! end4 ,) #cb ends ( ! wire project+ f ! end ( ! armature1 x is confus+ & mi/akes are (t5 made 9 ! connections1 s t "o or m coils may oppose ea* o!r :i* w\ld r$uce ! voltage4 ,aft] ! surface ( ! armature is cov]$ ) "o lay] x w be notic$ t ! numb] ( leads f ! coils to ! commutator b>s is only "o-half ! numb] ( b>s & t !y lie on "o-half ( ! armature4 ,9 ord] to complete ! w9d+ ! fir/ lay] %\ld be insulat$ & ! second lay] w\nd on4 ,! beg9n+ ( ! new coil w be directly ov] ! fir/ coil put on1 b ! beg9n+ ( ! new coil w be diametrically opposite ! beg9n+ ( ! fir/ coil w\nd4 ,! w9d+ is n[ cont9u$ section by section & z ea* coil is f9i%$ a loop or pair ( leads is left to connect to ea* b>4 ,:5 ! la/ coil is w\nd1 its end w be f\nd ly+ next to ! wire us$ 9 />t+ & %\ld be jo9$ to x & f9ally connect$ to b> numb] "o :]e ! />t 0 made4 ,illu/ration3 ,,fig4 #bgj4--;,develop$ view ( ! s]ies connect$ wave w\nd r+ armature %[n 9 fig4 #bfi4 ,) ! w9d+ & commutator connect$1 all ( ! coils are 9 s]ies & ! beg9n+ ( ! fir/ coil jo9s ! end ( ! la/ coil4 ,if a pair ( bru%es be n[ plac$ on ! commutator at opposite po9ts ! curr5t w fl[ into ! b> & !n divide betwe5 ! two leads connect$ to x1 half ( ! curr5t fl[+ ar\nd "o side & ! o!r half fl[+ ar\nd ! o!r half ( ! armature or 9 o!r words1 ! two halves ( ! armature are jo9$ 9 p>allel4 ,ques4 ,:at is ! objection to ! ,siem5s w9d+ j describ$8 ,ans4 ,x produces an unsightly head :]e ! wires pass ar\nd ! %aft & requires consid]able skill to make x appe> workmanlike4 ,ques4 ,h[ may ?is be avoid$8 ,ans4 ,by us+ ! *ord w9d+s ( ,froehli* or ,breguet1 :i* are improvem5ts ov] ! ,siem5s 9 appe>ance & are m easily c>ri$ out4 ,illu/ration3 ,,fig4 #bga4--;,end view ( an armature1 %[+ ! di/9ction betwe5 ,siem5s' w9d+ & *ord w9d+4 ,*ord ,w9d+4--,9 cases :]e ! front & back pit*es#b are s tak5 t ! av]age pit* diff]s consid]ably f ! value obta9$ by divid+ ! numb] ( inductors by ! numb] ( poles1 ! arrangem5t is call$ a *ord w9d+4 #b ,,note--,! t]m back pit* means ! numb] ( spaces betwe5 ! two inductors ( a coil4 ,= in/ance1 9 fig4 #bfg1 ! pit* is #c2 t is1 !re are ?ree spaces betwe5 say inductors #a & #d :i* =m "p ( ! coil ,a--#a--d--;,c4 ,x is call$ ! back pit* 9 di/9ction f ! front or commutator pit*1 :i* 9 ?is in/ance is #b4 ,9 ?is me?od ea* coil is laid on ! drum s z to cov] an arc ( ! armature surface ne>ly equal to ! angul> pit* ( ! poles2 x is sometimes call$ %ort pit* w9d+4 ,ques4 ,:at is ! diff]5ce betwe5 ! ,siem5s w9d+ & ! *ord w9d+8 ,ans4 ,?is is illu/rat$ 9 fig4 #bga1 :i* %[s "o end ( an armature4 ,9 ! ,siem5s w9d+1 a wire />t+1 say at ,a1 crosses ! head & ent]s ! slot m>k$ ,b4 ,if x ent]s slot ,c x is a *ord w9d+4 ,ques4 ,describe a *ord w9d+4 ,ans4 ,! w9d+ is />t$ 9 ! same mann] z describ$ 9 ! ,siem5s me?od1 only in/ead ( cross+ ! head & return+ 9 ! section diametrically opposite1 ! section ,a ,c1 fig4 #bga1 next to x is us$ = ! return ( ! wire to ! front end4 ,leads = connect+ to ! commutator are left at ! beg9n+ & end ( ea* section z be=e /at$ & ! only diff]5ce betwe5 ! two me?ods w be notic$ :5 ! fir/ lay] is ne>ly complete 9 t two sections ly+ next to ea* o!r h no wire 9 !m4 ,?is w cause ! w9d] to ?9k he has made a mi/ake1 b by cont9u+ ! w9d+ & fill+ 9 ^! blank spaces 9 regul> ord] :5 ! two lay]s are complet$1 all ! sections w be fill$ ) an equal numb] ( turns & !re w be ! requir$ numb] ( leads f ! coils to connect up to ! commutator b>s4 ,ques4 ,h[ _m pa?s 9 ! *ord w9d+ j describ$8 ,ans4 ,two4 ,multiplex ,w9d+s4--,an armature may be w\nd ) two or m indep5d5t sets ( coils4 ,in/ead ( indep5d5t commutators = ! sev]al w9d+s1 !y are comb9$ into "o hav+ two or m sets ( segm5ts int]plac$ ar\nd ! circumf]5ce4 ,?us1 9 ! case ( two w9d+s1 ! bru% comes 9 contact alt]nately ) segm5ts ( ea* set4 ,! bru% !n mu/ be l>ge en\gh to ov]lap at lea/ two segm5ts1 s z to collect curr5t f bo? w9d+s simultane\sly4 ,bo? w9d+s !n are always 9 ! circuit 9 p>allel4 ,ques4 ,:at is ! effect ( a multiplex w9d+8 ,ans4 ,x r$uces ! t5d5cy to sp>k+1 because only half ( ! curr5t is commutat$ at a "t1 & also because adjac5t commutator b>s belong to diff]5t w9d+s4 ,illu/ration3 ,,fig4 #bgb4--;,a progressive wave w9d+4 ,if ! front & back pit*es ( a wave w9d+ be su* t 9 trac+ ! c\rse ( ! w9d+ ?r\gh z _m coils z !re are pairs ( poles1 a segm5t is rea*$ 9 advance ( ! "o f :i* ! />t 0 made1 ! w9d+ is said to be progressive4 ,! figure %[s ?ree coils ( a w9d+ hav+ #ah inductors4 ,f ! def9ition1 ! numb] ( coils to consid] to det]m9e if ! w9d+ be progressive is equal to ! numb] ( poles divid$ by #b1 :i* 9 ?is case is equal to #b4 ,^! coils are %[n 9 ! figure z foll[s3 ,a--#a--d--;,f & ,f--#aa--ad--;,b4 ,! second coil ends at segm5t ,b :i* is 9 advance ( segm5t ,a f :i* ! w9d+ began1 indicat+ t ! w9d+ is progressive4 ,fig4 #bgb is giv5 simply to illu/rate ! def9ition ( a progressive w9d+1 & n to repres5t a practical w9d+4 ,ques4 ,does an accid5t to "o w9d+ disable ! ma*9e8 ,ans4 ,no1 x simply r$uces its curr5t capacity4 ,ques4 ,c multiplex w9d+s h m ?an two w9d+s8 ,ans4 ,yes1 !re may be ?ree or f\r w9d+s4 ,ques4 ,:at is ! objection to increas+ ! numb] ( w9d+s8 ,ans4 ,x involves an increas$ numb] ( inductors & commutator segm5ts1 :i* is undesirable 9 small ma*9es1 b = l>ge ones might be all[able4 ,illu/ration3 ,,fig4 #bgc4--;,a retrogressive wave w9d+4 ,if ! pit*es be su* t 9 trac+ ! w9d+ ?r\gh z _m coils z !re are pairs ( poles1 ! fir/ segm5t ( ! commutator is n enc\nt]$ or pass$ ov]1 ! w9d+ is said to be retrogressive4 ,! numb] ( coils to consid] is two1 z foll[s3 ,a-#a-d-;,d & ,d-#g-aj-;,g4 ,! second coil ends at ,g1 h5ce1 s9ce ! segm5t ,a :]e ! />t 0 made has n be5 rea*$ or pass$ ov] ! w9d+ is retrogressive4 ,fig4 #bgc is giv5 simply to illu/rate ! def9ition ( retrogressive w9d+1 & n to repres5t a practical w9d+4 ,:5 !re are two indep5d5t w9d+s ! arrangem5t is call$ duplex1 ) ?ree w9d+s1 triplex1 & ) f\r1 quadruplex4 ,ques4 ,:at loss is r$uc$ ) multiplex w9d+s8 ,ans4 ,9 ^! w9d+s1 ! division ( :at o!rwise w\ld be v /\t inductors into sev]al small] ones1 has ! effect ( r$uc+ eddy curr5t loss4 ,ques4 ,= :at s]vice are ma*9es ) multiplex w9d+s specially adapt$8 ,ans4 ,multiplex w9d+s are us$ 9 ma*9es int5d$ to supply l>ge curr5ts at l[ voltages1 su* z is requir$ 9 electrolytic "w4 ,numb] ( ,bru%es ,requir$4--,! numb] ( places on ! commutator at :i* x is necess>y or advisable to place a set ( collect+ bru%es c be asc]ta9$ f ! w9d+ diagrams4 ,all t is necess>y is to draw arr[s m>k+ ! directions ( ! induc$ electromotive =ces4 ,:]ev] two arr[ heads meet at any segm5t ( ! commutator1 a positive bru% is to be plac$1 & at e po9t f :i* two arr[s />t 9 oppos$ directions along ! w9d+1 a negative bru% %\ld be plac$4 ,ques4 ,h[ _m bru%es are requir$ = lap w9d+s & ord9>y p>allel r+ w9d+s8 ,ans4 ,!re w be z _m bru%es z poles1 & !y w be situat$ symmetrically ar\nd ! commutator 9 regul> ord] & at angul> di/ances ap>t equal to ! pole pit*4 ,x %\ld be not$ t ! numb] ( bru% sets does n necess>ily %[ ! numb] ( circuits ?r\gh ! armature4 ,ques4 ,h[ _m bru%es are requir$ = wave w9d+s8 ,ans4 ,if arr[s be drawn m>k+ ! direction ( ! induc$ electromotive =ces to det]m9e ! numb] ( bru%es1 x w be f\nd t only two bru%es are requir$ = any numb] ( poles4 ,ques4 ,:at is ! angle betwe5 ^! two bru%es8 ,ans4 ,x is ! same z ! angle betwe5 any nor? & s\? pole4 ,= in/ance1 9 a t5 pole ma*9e ) wave w9d+ ! pit* betwe5 ! bru%es may be any ( ! foll[+ angles3 #cfj #aj #cf #c #cf #ajh #e #cf #ahj ,illu/ration3 ,,figs4 #bgd & #bge4--,"r & left h& w9d+s4 ,^! consi/ respectively ( turns :i* pass ar\nd ! core 9 a "r or left h&$ fa%ion4 ,?us 9 fig4 #bgd1 9 pass+ ar\nd ! circle clockwise f a to b1 ! pa? ( ! w9d+ is a "r h&$ spiral4 ,9 fig4 #bge1 :i* %[s "o coil ( a drum armature1 if a be tak5 z ! />t+ po9t1 9 go+ to b1 a mu/ be connect$ by a spiral connector across ! front end ( ! drum to "o ( ! desc5d+ inductors su* z ,m1 f :i* at ! back end ano!r connector mu/ jo9 x to "o ( ! asc5d+ inductors1 su* z ,s1 :]e x is l$ to b1 ?us mak+ "o "r h&$ turn4 ,sometimes ) lap w9d+ x is desirable to r$uce ! numb] ( bru%es4 ,9 fig4 #bgf1 is %[n ! di/ribution ( curr5ts 9 a f\r pole lap w\nd ma*9e hav+ f\r bru%es & g5]at+ #abj amp]es4 ,9 ea* ( ! f\r circuits ! fl[ is #cj amp]es1 & ! curr5t deliv]$ to ea* bru% is #fj amp]es4 ,if n[ two ( ! bru%es be remov$1 ! curr5t ?r\gh ea* ( ! rema9+ two w be #abj amp]es1 :ile int]nally !re w be only two circuits z %[n 9 fig4 #bgg4 ,x %\ld be not$1 h[ev]1 t ^! two circuits d n take equal %>es ( ! curr5t s9ce1 ?\gh ! sum ( ! electromotive =ces 9 ea* circuit is ! same1 ! resi/ance ( "o is ?ree times t ( ! o!r1 giv+ #ij amp]es 9 "o & #cj amp]es 9 ! o!r1 z indicat$ 9 ! figure4 ,if no sp>k difficulties occur 9 collect+ all ! curr5t ) only two bru%es1 ! arrangem5t w "w satisfactorily1 b ! heat losses w be great] ?an ) f\r bru%es4 ,illu/ration3 ,,fig4 #bgf4--;,di/ribution ( armature curr5ts 9 a f\r pole lap w\nd dynamo hav+ f\r bru%es & g5]at+ #abj amp]es4 ,ques4 ,are m ?an two bru%es ev] us$ ) wave w9d+8 ,ans4 ,x is sometimes advisable to use m ?an two bru%es ) wave w9d+s1 especially :5 ! curr5t is v l>ge4 ,= in/ance1 9 ! case ( a s+ly re-entrant#c simplex wave w9d+ = an eight pole ma*9e1 :5ev] any bru% bridges adjac5t b>s ( ! commutator1 x %ort circuits "o r\nd ( ! wave w9d+ & ?is r\nd is connect$ at ?ree int]m$iate po9ts to o!r b>s ( ! commutator4 ,h5ce1 if ! %ort circuit+ bru% be a positive bru%1 no h>m w be done by ?ree o!r positive bru%es t\*+ at ! o!r po9ts4 ,if ^! o!r bru%es be broad en\gh to bridge across two commutator b>s1 !y may effect commutation1 t is1 ?ree r\nds in/ead ( "o und]go+ commutation toge!r4 #c ,,note4--,a re-entrant w9d+ is "o 9 :i* bo? ends re-ent] or lead back to ! />t+ po9t2 a clos$ w9d+4 ,numb] ( ,armature ,circuits4--,x is possible to h w9d+s t give any desir$ ev5 numb] ( circuits 9 ma*9es hav+ any numb] ( poles4 ,illu/ration3 ,,fig4 #bgg4--,%[+ effect ( remov+ two ( ! bru%es 9 fig4 #bge4 ,if no sp>k difficulties occur 9 collect+ ! curr5t ) only two bru%es1 ! arrangem5t w "w satisfactorily1 b ! heat losses w be great] ?an ) f\r bru%es4 ,ques4 ,h[ _m pa?s are possible 9 p>allel8 ,ans4 ,= a simplex spirally w\nd r+1 ! numb] ( pa?s 9 p>allel is equal to ! numb] ( poles1 & = a simplex s]ies w\nd r+1 !re w be two pa?s4 ,9 ! case ( multiplex w9d+s ! numb] ( pa?s is equal to t ( ! simplex w9d+ multipli$ by ! numb] ( indep5d5t w9d+s4 ,9 l>ge multipol> dynamos x is1 z a rule1 inadvisable to h m ?an #ajj or #aej amp]es 9 any "o circuit1 except 9 ! case ( special ma*9es = electro-*emical "w4 ,su* consid]ations are factors :i* gov]n ! *oice ( numb] ( circuits4 ,equaliz] ,r+s4--,^! are r+s resembl+ a s]ies ( hoops provid$ 9 a p>allel w\nd armature to elim9ate ! effects ( unbalanc+1 by :i* ! curr5t divides unequally among ! sev]al pa?s ?r\gh ! armature4 ,by means ( leads1 equaliz] r+s connect po9ts ( equal pot5tial 9 ! w9d+ & s pres]ve an equalization ( curr5t4 ,illu/ration3 ,,fig4 #bgh4--,re> view ( armature ( a l>ge dynamo built by ! ,g5]al ,electric ,co41 %[+ equaliz] r+s4 ,ques4 ,9 multipol> ma*9es :at po9ts are connect$ by equaliz] r+s8 ,ans4 ,any two or m po9ts 9 ! w9d+1 t dur+ ! rotation1 are at ne>ly equal pot5tials4 ,if !re 7 p]fect symmetry 9 ! field sy/em1 no curr5ts w\ld fl[ along su* connectors2 h[ev]1 ow+ to imp]fect symmetry1 ! induction 9 ! v>i\s sections ( ! w9d+ may be unequal & ! curr5ts n equally di/ribut$4 ,drum ,w9d+ ,requirem5ts4--,!re are sev]al conditions t mu/ be satisfi$ by a clos$ coil drum w9d+3 #a4 ,!re _c be an odd numb] ( inductors2 ,an odd numb] ( inductors w\ld be equival5t to n hav+ a :ole numb] ( coils4 ,! ev5 numb]$ inductors may be reg>d$ z ! returns = ! odd numb]$ inductors4 #b4 ,bo? ! front & back pit*es mu/ be odd 9 simplex w9d+s4 #c4 ,! av]age pit* %\ld be approximately equal to ! numb] ( inductors divid$ by ! numb] ( poles4 ,?is condition mu/ obta9 9 ord] t ! electric pressures induc$ 9 inductors mov+ simultane\sly "u poles ( opposite sign1 w be add$4 ,! smalle/ pit* meet+ ?is condition w\ld /ret* completely across a pole face1 :ile ! l>ge/ w\ld /ret* f ! giv5 pole tip to ! next pole tip ( l pol>ity4 ,! *oice ( front & back pit* = a giv5 numb] ( inductors %\ld1 ) lap & wave w9d+s 9 g5]al1 comply ) ! foll[+ conditions3 #a4 ,all ! coils compos+ ! w9d+ mu/ be simil>1 bo? me*anically & electrically1 & mu/ be arrang$ symmetrically ^u ! armature4 #b4 ,ea* inductor ( a simplex w9d+ mu/ be enc\nt]$ once only1 & ! w9d+ mu/ be re-entrant4 #c4 ,ea* simplex w9d+ compos+ a multiplex w9d+ mu/ fulfill ! requirem5t = a simplex w9d+4 #d4 ,a s+ly re-entrant multiplex w9d+ mu/ z a :ole satisfy ! requirem5t = a simplex w9d+4 ,9 addition to ! above requirem5ts = lap & wave w9d+s 9 g5]al1 lap w9d+s mu/ comply ) ! foll[+ conditions3 #a4 ,! front & back pit*es mu/ be opposite 9 sign2 #b4 ,! front & back pit*es mu/ be unequal2 ,if !y be equal1 ! coil w\ld be %ort circuit$ ^u itself4 #c4 ,! front & back pit*es mu/ diff] by two2 #d4 ,9 multiplex w9d+s1 ! front & back pit*es mu/ diff] by two multipli$ by ! numb] ( indep5d5t simplex w9d+s compos+ ! multiplex w9d+2 #e4 ,! numb] ( slots on a slott$ armature may be ev5 or odd2 #f4 ,! numb] ( inductors mu/ be an ev5 numb]2 x may be a multiple ( ! numb] ( slots2 ,9 ! case ( wave w9d+s ! sev]al conditions to be fulfill$ may be /at$ z foll[s3 #a4 ,! front & back pit*es mu/ be alike 9 sign2 #b4 ,! front & back pit*es may be equal or !y may diff] by any multiple ( two4 ,!y are usually made ne>ly equal to ! numb] ( inductors divid$ by ! numb] ( poles4 ,,*apt] ,,xix ,,!ory ,,( ,,! ,,armature ,curr5t ,di/ribution 9 ,r+ & ,drum ,armatures4--,9 /udy+ ! actions & reactions :i* take place 9 ! armature1 ! /ud5t %\ld be able to det]m9e ! directions ( ! induc$ curr5ts4 ,! basic pr9ciples ( electromagnetic induction 7 giv5 9 *apt] ,x1 f :i*1 = in/ance1 ! di/ribution ( curr5t 9 ! gramme r+ armature1 %[n 9 fig4 #bgi1 is easily det]m9$ by ! application ( ,flem+'s rule4 ,trac+ ! curr5t f ! negative to ! positive bru%1 x w be se5 t x divides1 half go+ ?r\gh coils #a1 #b1 #c1 & half ?r\gh coils ,i1 ,,ii1 ,,iii1 ^! two curr5ts asc5d to ! top ( ! r+1 unit+ at ! positive bru%4 ,ques4 ,9 ! ,gramme r+ armature 7fig4 #bgi7 :at is ! di/ribution ( armature curr5ts8 ,ans4 ,!re are two pa?s 9 p>allel z indicat$ 9 fig4 #bgi4 ,ques4 ,h[ does ! voltage v>y 9 ! coils8 ,ans4 ,x v>ies accord+ to ! position ( ! coils1 be+ lea/ :5 v]tical & greate/ :5 horizontal 9 a two pole ma*9e arrang$ z 9 fig4 #bgi4 ,! upp] & l[] coils 9 ! "r h& half ( ! r+ armature1 fig4 #bgi1 w h ab\t ! same electromotive =ce induc$ 9 !m1 say #b volts ea*1 :ile ! two coils betwe5 !m w h a high] electromotive =ce1 at ! same in/ant1 say #d volts ea*1 s9ce !y occupy ne>ly ! positions ( ! maximum rate ( *ange ( ! magnetic l9es ?read+ ?r\gh !m4 ,^! eight coils may be repres5t$ by two batt]ies connect$ 9 p>allel1 ea* batt]y consi/+ ( two #b volt cells & two #d volt cells z %[n 9 fig4 #bhj4 ,! voltage ( ea* batt]y !n w be #b #d #d #b #ab volts ,illu/ration3 ,,fig4 #bgi4--;,curr5t di/ribution 9 a gramme r+ armature4 ,!re are two pa?s = ! curr5t betwe5 ! bru%es1 half go+ up ea* side ( ! r+ z indicat$ by ! arr[s1 ?us giv+ two pa?s 9 p>allel z indicat$ 9 fig4 #bha4 ,illu/ration3 ,,fig4 #bhj4--;,batt]y analogy illu/rat+ curr5t di/ribution 9 a r+ armature4 ,! eight coils ( ! armature1 fig4 #bgi1 are repres5t$ by two batt]ies ( f\r cells ea*4 ,! action ( ! two units ?us connect$ is indicat$ by ! arr[s4 ,9 ! ext]nal circuit ! voltage is equal to t ( "o batt]y & ! curr5t is equal to ! sum ( ! curr5ts 9 ea* batt]y4 ,! two batt]ies be+ connect$ 9 p>allel1 ! voltage at ! t]m9als w be ! same1 b ! curr5t w be ! sum ( ! curr5ts 9 ea* batt]y4 ,ques4 ,h[ may ! numb] ( pa?s 9 p>allel be increas$8 ,ans4 ,by increas+ ! numb] ( poles4 ,= in/ance1 9 a f\r pole ma*9e1 z 9 fig4 #bhc1 !re are f\r pa?s 9 p>allel4 ,9 ?is case ! armature may be us$ to furni% two sep>ate curr5ts1 ?\gh ?is is n desirable4 ,illu/ration3 ,,fig4 #bha4--;,diagram %[+ di/ribution ( curr5t 9 ! gramme r+ armature ( fig4 #bgi4 ,! curr5t fl[s 9 two p>allel pa?s z indicat$4 ,illu/ration3 ,,fig4 #bhb4--;,diagram %[+ curr5t di/ribution ?r\gh armature ( a f\r pole ma*9e ) l bru%es connect$4 ,!re are f\r pa?s 9 p>allel1 h5ce ! induc$ voltage w equal t ( "o set ( coils1 & ! curr5t w be f\r times t fl[+ 9 "o set ( coils4 ,ques4 ,h[ are ! bru%es connect$8 ,ans4 ,usually all ! positive bru%es are connect$ toge!r1 & all ! negative bru%es z 9 fig4 #bhc1 giv+ f\r pa?s 9 p>allel ?r\gh ! armature z indicat$ 9 fig4 #bhb4 ,illu/ration3 ,,fig4 #bhc4--;,bru% connections = f\r pole dynamo4 ,x is usual to connect all ! positive bru%es to "o t]m9al & all ! negative bru%es to ! o!r :i* gives f\r p>allel pa?s z %[n 9 ! diagram1 fig4 #bhb4 ,9 a f\r pole ma*9e1 two sep>ate curr5ts c be obta9$ by omitt+ ! p>allel bru% connections4 ,ques4 ,h[ does ?is me?od ( bru% connection affect ! voltage8 ,ans4 ,! voltage at ! t]m9als is equal to t ( any ( ! sets ( coils betwe5 "o positive bru% & ! adjac5t negative bru%4 ,?us 9 ! f\r pole ma*9e1 fig4 #bhc1 ! coils ( ! f\r quadrants are 9 f\r p>allels1 :i* gives an int]nal resi/ance equal to "o-sixte5? t ( ! total resi/ance ( ! entire r+4 ,:5 ! coils are connect$ 9 two circuits or s]ies p>allel1 x requires only two bru%es at two neutral po9ts on ! commutator1 = any numb] ( poles2 ?is arrangem5t is %[n 9 fig4 #bfi4 ,ques4 ,9 g5]al :at may be said ab\t ! curr5t pa?s ?r\gh an armature8 ,ans4 ,! pa?s may be 9 p>allel or s]ies p>allel accord+ z ! w9d+ is ( ! lap or wave type4 ,illu/ration3 ,,fig4 #bhd4--,morday's me?od ( measur+ ! v>iation ( voltage ar\nd ! commutator by use ( a s+le explor+ bru% & volt met]4 ,x consi/s 9 connect+ "o t]m9al ( ! volt met] 7pref]ably an electro/atic "o7 to "o bru% ( ! ma*9e1 & ! o!r t]m9al to ! explor+ bru%1 :i* c be mov$ f po9t to po9t1 read+s be+ tak5 at ea* po9t4 ,v>iation ( ,voltage ,ar\nd ! ,commutator4--,!re are num]\s ways ( det]m9+ ! value ( ! induc$ voltage 9 an armature at v>i\s po9ts ar\nd ! commutator4 ,9 ! me?od sugge/$ by ,morday1 x c be measur$ by ! use ( a s+le explor+ bru% & a volt met] z %[n 9 fig4 #bhd4 ,9 ?is me?od1 "o t]m9al ( ! volt met] is connect$ to "o ( ! bru%es ( ! dynamo1 & ! o!r t]m9al is jo9$ by a wire to a small pilot bru% :i* c be press$ aga9/ ! commutator at any desir$ "p ( its circumf]5ce4 ,) ! ma*9e runn+ at its rat$ spe$1 ! explor+ bru% is plac$ 9 successive positions betwe5 ! two bru%es ( ! ma*9e4 ,9 ea* position a read+ ( ! volt met] is tak5 & ! angul> position ( ! explor+ bru% not$4 ,illu/ration3 ,,fig4 #bhe4--;,cross magnetization4 ,?is is def9$ z l9es ( magnetic =ce set up 9 ! w9d+s ( a dynamo armature :i* oppose at "r angles ! l9es ( =ce creat$ betwe5 ! poles ( ! field magnet4 ,! figure %[s ?is cross flux :i* is due to ! armature curr5t alone4 ,ques4 ,h[ does ! voltage v>y betwe5 successive pairs ( commutator segm5ts8 ,ans4 ,! v>iation is n con/ant4 ,cross ,magnetization2 ,field ,di/ortion4--,9 ! op]ation ( a dynamo ) load1 ! induc$ curr5t fl[+ 9 ! armature w9d+1 conv]ts ! armature into an electromagnet sett+ up a field across or at "r angles to ! field ( ! ma*9e4 ,?is cross magnetization ( ! armature t5ds to di/ort ! field produc$ by ! field magnets1 ! effect be+ kn[n z armature reaction4 ,to und]/& ! nature ( ?is reaction x is be/ to fir/ consid] ! effect ( ! field curr5t & ! armature curr5t sep>ately4 ,fig4 #bhe repres5ts ! magnetic flux ?r\gh an armature at re/1 :]e ! field magnets are sep>ately excit$4 ,if ! armature be rotat$ clockwise1 induc$ curr5ts w fl[ upw>d ?r\gh ! two halves ( ! w9d+ betwe5 ! bru%es1 mak+ ! l[] bru% negative & ! upp] bru% positive4 ,ques4 ,if1 9 fig4 #bhe1 ! curr5t 9 ! field magnet be %ut (f1 & a curr5t be pass$ ?r\gh ! armature ent]+ at ! l[] bru%1 :at is ! effect8 ,ans4 ,! curr5t w divide at ! l[] bru%1 fl[+ up ea* side to ! top bru%4 ,^! curr5ts t5d to produce nor? & s\? poles on ea* half ( ! core at ! po9ts :]e ! curr5t ent]s & leaves ! armature4 ,h5ce1 !re w be two nor? poles at ! top ( ! r+ & two s\? poles at ! bottom4 ,ques4 ,:at effect is produc$ by ! l poles at ! top & bottom ( ! r+8 ,ans4 ,! ext]nal effect w be ! same z ?\gh !re 7 a s+le nor? & s\? pole situat$ respectively at ! top & bottom ( ! r+4 ,ques4 ,9 ! op]ation ( a dynamo1 h[ d ! poles induc$ 9 ! armature affect ! magnetic field ( ! ma*9e8 ,ans4 ,!y di/ort ! l9es ( =ce into an oblique direction z %[n exagg]at$ 9 ! diagram fig4 #bhf4 ,illu/ration3 ,,fig4 #bhf4--;,di/ortion ( magnetic field due to cross magnetization4 ,= cle>ness1 ! effect is %[n some:at exagg]at$4 ,a drag or resi/ance to ! movem5t ( ! armature is caus$ by ! attraction ( ! nor? & s\? poles on ! armature & pole pieces respectively4 ,ques4 ,:at effect has ! pres5ce ( poles 9 ! armature on ! op]ation ( ! ma*9e8 ,ans4 ,9 fig4 #bhf1 ! resultant nor? pole n1 n1 n1 :]e ! l9es em]ge f ! r+1 attracts ! s\? pole1 s1 s1 s1 :]e ! l9es ent] ! field magnet1 h5ce a load is br\ght ^u ! eng9e1 :i* drives ! dynamo1 9 dragg+ ! armature ar\nd aga9/ ^! attractions4 ,! /rong] ! curr5t induc$ 9 ! armature1 ! great] w be ! p[] necess>y to turn x4 ,ques4 ,:y does ?is reaction 9 ! armature require m p[] to drive ! ma*9e8 ,ans4 ,! effect produc$ by ! armature reaction is 9 accordance ) ,l5z's law :i* /ates t3 ,9 electromagnetic induction1 ! direction ( ! induc$ curr5t is su* z to oppose ! motion produc+ x4 ,illu/ration3 ,,fig4 #bhg4--;,actual di/ortion ( field result+ f cross magnetization1 z %[n by iron fil+s4 ,rem$ies = ,field ,di/ortion4--,s9ce ! di/ortion ( ! magnetic field ( a dynamo causes unsatisfactory op]ation1 num]\s attempts h be5 made to ov]come ?is defect1 z = in/ance1 by3 #a4 ,exp]im5t+ ) diff]5t =ms ( pole piece2 ,! reluctance ( ! pole piece %\ld be increas$ 9 ! region :]e ! magnetic flux t5ds to become mo/ d5se4 ,! trail+ horn ( ! pole piece may be made long] ?an ! advanc+ horn & cut f>!r f ! surface ( ! armature1 s z to equalize ! di/ribution ( ! magnetic flux4 #b4 ,l5g!n+ ! air gap2 ,?is increases ! reluctance1 & also necessitates m amp]e turns 9 ! field w9d+4 ,! field di/ortion1 h[ev]1 w n be s great1 z x w\ld be if ! magnetic field ( ! ma*9e 7 weak]4 #c4 ,slott+ ! pole pieces2 ,bo? longitud9al gaps & oblique slots h be5 tri$4 ,! r$uction ( cross section ( ! pole piece causes x to become highly saturat$ & to (f] l>ge reluctance to ! cross field4 #d4 ,! use ( auxili>y poles4 ,^! are small poles plac$ betwe5 ! ma9 poles & s w\nd & connect$ t _! action opposes t ( ! cross field4 ,normal ,neutral ,plane4--,?is may be def9$ z a plane pass+ ?r\gh ! axis ( ! armature p]p5dicul> to ! magnetic field ( ! ma*9e :5 !re is no fl[ ( curr5t 9 ! armature1 z %[n 9 fig4 #bhh4 ,x is ! plane 9 :i* ! bru%es w\ld be plac$ to prev5t sp>k+ :5 ! ma*9e is 9 op]ation 7 ! field n di/ort$ by armature reaction1 & !re 7 no self-induction 9 ! coils4 ,commutat+ ,plane2 ,lead ( ! ,bru%es4--,x has be5 f\nd t 9 ord] to r$uce sp>k+ to a m9imum1 ! bru%es mu/ be plac$ 9 c]ta9 positions f\nd by trial & designat$ z be+ locat$ 9 ! neutral plane4 ,:5 ! bru%es are 9 ! neutral plane1 !y are 9 contact ) commutator segm5ts connect+ ) coils t are cutt+ ! l9es ( =ce at ! m9imum rate4 ,ques4 ,def9e ! t]m commutat+ plane4 ,ans4 ,?is is a plane pass+ ?r\gh ! axis ( ! armature & ?r\gh ! c5t] ( contact ( ! bru%es z %[n 9 figs4 #bhi & #cjj4 ,ques4 ,:at is ! angle ( lead8 ,ans4 ,! angle betwe5 ! normal neutral plane & ! commutat+ plane4 ,9 ! op]ation ( a dynamo s9ce ! field1 on acc\nt ( armature reaction1 is twi/$ ar\nd 9 ! direction ( rotation1 ! prop] position = ! bru%es is no long] 9 ! normal neutral plane1 b lies obliquely across1 a few degrees 9 advance4 ,h5ce1 = sp>kless commutation1 ! commutat+ plane is a little 9 advance ( ! normal neutral plane1 ! lead be+ measur$ by ! angle betwe5 ^! planes1 z /at$ 9 ! def9ition4 ,illu/ration3 ,,fig4 #bhh4--,normal neutral plane4 ,?is is a ref]5ce plane f :i* ! lead is measur$4 ,z %[n1 ! normal neutral plane lies at "r angles to ! l9es ( =ce ( an undi/ort$ field4 ,ques4 ,:at may be said ) respect to ! angle ( lead8 ,ans4 ,= sp>kless commutation1 ! angle ( lead v>ies ) ! load4 ,if ! field be mu* alt]$ at full load1 x is evid5t t at half or qu>t] load x w n be ne>ly s mu* twi/$1 h5ce ! necessity = m\nt+ ! bru%es on "s k9d ( rock+ device :i* w all[ !m to be %ift$ 9 diff]5t positions = diff]5t loads4 ,a desirable po9t1 !n1 9 dynamo design is to make ! angle ( lead at full load s small t x w n be necess>y to %ift ! bru%es mu* = v>iation ( load4 ,?is c be accompli%$ by mak+ ! field magnet field consid]ably m p[]ful ?an ! armature field4 ,illu/ration3 ,,fig4 #bhi4--;,diagram illu/rat+ ! demagnetiz+ effect ( armature reaction4 ,?is results f ! =w>d lead giv5 ! bru%es 9 ord] to secure sp>kless commutation4 ,demagnetiz+ ,effect ( ,armature ,reaction4--,9 ! op]ation ( a dynamo1 z previ\sly expla9$1 ! position ( ! bru%es = sp>kless commutation mu/ be v>i$ ) ! load2 t is1 = light load !y %\ld occupy a position practically midway betwe5 ! poles & = a heavy load !y mu/ be mov$ a few degrees 9 ! direction ( rotation4 ,9 o!r words1 ! commutat+ plane mu/ be m or less 9 advance ( ! normal neutral plane z %[n 9 fig4 #bhi4 ,ques4 ,:at is ! effect ( lead8 ,ans4 ,x produces a demagnetiz+ effect :i* t5ds to weak5 ! field magnets4 ,ques4 ,describe ?is demagnetiz+ effect 9 detail4 ,ans4 ,trac+ ! armature curr5ts1 9 fig4 #bhi accord+ to ,flem+'s rule1 x w be se5 t curr5t 9 inductors #a to #ah fl[ f ! obs]v] indicat$ by crosses repres5t+ ! tails ( retreat+ arr[s & 9 inductors #ai to #cf1 t[>d ! obs]v] f ! back ( armature1 indicat$ by dots repres5t+ ! po9ts ( approa*+ arr[s4 ,9 det]m9+ ^! curr5t directions ! inductors to ! "r ( ! neutral l9e are consid]$ z mov+ d[nw>d1 & ^? to ! left z mov+ upw>d4 ,! curr5t 9 inductors #a to #ae & #ai to #cc1 t5ds to cross magnetize ! magnetic field ( ! ma*9e1 b ! curr5t 9 inductors #cd to #cf & #af to #ah t5ds to produce nor? & s\? poles z indicat$4 ,^! poles are 9 opposition to ! field poles & t5d to demagnetize !m4 ,h5ce1 ! inductors ly+ outside ! two upright l9es are kn[n z cross magnetiz+ turns1 & ^? ly+ inside1 z demagnetiz+ turns4 ,! bread? ( ! belt ( demagnetiz+ turns includ$ betwe5 ! two upright l9es is cle>ly proportional to ! angle ( lead2 !re=e1 ! demagnetiz+ effect increases ) ! lead4 ,eddy ,curr5ts2 ,lam9ation4--,induc$ electric curr5ts1 kn[n z eddy curr5ts1 occur :5 a solid metallic mass is rotat$ 9 a magnetic field4 ,!y consume consid]able en]gy & (t5 occasion h>mful rise 9 temp]ature4 ,armature cores1 pole pieces1 & field magnet cores are specially subject to ^! curr5ts4 ,illu/ration3 ,,fig4 #bij4--;,arago's exp]im5t illu/rat+ eddy curr5ts4 ,arago f\nd t if a copp] disc be rotat$ 9 its own plane und]nea? a compass ne$le1 ! ne$le 0 dragg$ ar\nd z by "s invisible friction4 ,! explanation ( ?is ph5om5on1 kn[n z ,arago's rotations1 is due to ,f>aday1 :o discov]$ t x 0 caus$ by induction4 ,t is1 a magnet mov$ ne> a solid mass ( metal1 induces 9 x curr5ts1 :i*1 9 fl[+ f "o po9t to ano!r1 h _! en]gy conv]t$ into heat1 & :i*1 :ile !y la/1 produce 79 accordance ) ,l5z's law7 electromotive =ces t5d+ to /op ! motion4 ,?us1 9 ! figure1 !re are a pair ( eddies 9 ! "p pass+ betwe5 ! poles1 & ^! curr5ts oppose ! motion ( ! disc4 ,f\cault %[$ by exp]im5t ! heat+ effect ( eddy curr5ts1 b su* curr5ts 7 kn[n ye>s be=e ,f\cault's exp]im5ts1 h5ce !y are incorrectly call$ ,f\cault curr5ts4 ,ques4 ,describe ! =mation ( eddy curr5ts4 ,ans4 ,9 fig4 #bia1 a b> inductor is se5 j pass+ f "u ! tip ( ! pole piece ,n ( ! field magnet4 ,not+ ! di/ribution ( ! l9es ( =ce1 x w be se5 t ! edge c d is 9 a weak] field ?an ! edge a b1 h5ce1 s9ce ! two edges move ) ! same velocity1 ! electromotive =ce induc$ along c d w be less ?an t induc$ along a b4 ,?is gives rise to :irls or curr5t eddies 9 ! copp] b> z %[n4 ,illu/ration3 ,,fig4 #bia4--;,=mation ( eddy curr5ts 9 a solid b> inductor4 ,on acc\nt ( its appreciable size1 ! field is sometimes weak] at "o po9t ?an ano!r1 h5ce ! unequal electromotive =ces ?us produc$ w induce eddy curr5ts4 ,ques4 ,:at %\ld be not$ 9 seek+ a rem$y = eddy curr5ts8 ,ans4 ,x %\ld be not$ t eddy curr5ts are due to v small diff]5ces ( pressure & t ! curr5ts are l>ge only because ( ! v l[ resi/ance ( _! circuits4 ,ques4 ,:at is ! be/ means ( r$uc+ eddy curr5ts8 ,ans4 ,lam9ation4 ,ques4 ,expla9 ?is mode ( con/ruction ) respect to ! b> inductor fig4 #bia4 ,ans4 ,9 ! case ( a l>ge b> inductor su* z %[n 9 fig4 #bia1 x c\ld be replac$ by a numb] ( small wires sold]$ toge!r only at ! ends4 ,! lay] ( dirt or oxide on ! outside ( ! wires w furni% suffici5t resi/ance to practically prev5t ! eddy curr5ts pass+ f wire to wire4 ,illu/ration3 ,,fig4 #bib4--;,eddy curr5ts induc$ 9 a solid armature core4 ,eddy curr5ts always occur :5 a solid metallic mass is rotat$ 9 a magnetic field1 because ! out] portion ( ! metal cuts m l9es ( =ce ?an ! inn] portion1 h5ce ! induc$ electromotive =ce n be+ uni=m1 t5ds to set up curr5ts betwe5 ! po9ts ( greate/ & lea/ pot5tial4 ,eddy curr5ts consume a consid]able am\nt ( en]gy & (t5 occasion h>mful rise 9 temp]ature4 ,ques4 ,h[ %\ld an armature core be lam9at$ to avoid eddy curr5ts8 ,ans4 ,x %\ld be lam9at$ at "r angles to its axis4 ,fig4 #bib %[s ! induc$ eddy curr5ts 9 a solid armature core1 & fig4 #bic %[s ! mann] 9 :i* ! pa?s ( ^! curr5ts are int]rupt$ & ! losses due to _! effect dim9i%$ by ! use ( lam9at$ cores4 ,illu/ration3 ,,fig4 #bic4--;,armature core ) a few lam9ations %[+ effect on eddy curr5ts4 ,9 practice ! core is made up ( a great numb] ( ?9 %eet metal discs1 ab\t #ah gauge1 :i* introduces s mu* resi/ance betwe5 ! discs t ! =mation ( eddy curr5ts is almo/ entirely prev5t$4 ,9 fig4 #bic1 only five lam9ations or plates are indicat$1 s z to %[ ! sub-division ( ! eddy curr5ts1 b 9 practical armatures1 ! numb] ( lam9ations or pun*+s ranges f #dj to #ff to an in*1 & br+s ! eddy curr5t loss d[n to ab\t "o p] c5t4 ,a great] increase 9 ! numb] ( lam9ations p] in* is n economical1 h[ev]1 ow+ to ! difficulties enc\nt]$ 9 ! pun*+ & h&l+ ( extremely ?9 %eets ( iron1 & ! loss ( space betwe5 ! plates4 ,armature cores con/ruct$ ( ! numb] ( plates /at$1 & =c$ toge!r by means ( screws & heavy hydraulic pressure1 conta9 f #hj to #ij p] c5t4 ( iron1 & h a magnetic flux c>ry+ capacity only f #e to #ae p] c5t4 less ?an :5 !y are made ( an equal volume ( solid iron4 ,magnetic ,drag on ! ,armature4--,:5ev] a curr5t is induc$ 9 an armature coil by mov+ x 9 ! magnetic field s z to cut l9es ( =ce1 ! direction ( ! induc$ curr5t is su* z to oppose ! motion produc+ x4 ,h5ce1 9 ! op]ation ( a dynamo1 consid]able driv+ p[] is requir$ to ov]come ?is magnetic drag on ! armature4 ,illu/ration3 ,,fig4 #bid4--;,circul> conc5tric magnetic field surr\nd+ a conductor c>ry+ a curr5t4 ,if ?is conductor be mov$ across a magnetic field1 z betwe5 ! poles ( a magnet1 ! l9es ( =ce w be di/ort$ z 9 fig4 #bie1 :i* w oppose ! motion ( ! conductor4 ,a conductor c>ry+ a curr5t is surr\nd$ by a circul> conc5tric magnetic field4 ,if n[ su* a conductor1 ) curr5t fl[+ t[>d ! obs]v] z 9 fig4 #bid1 be plac$ 9 a uni=m magnetic field1 a di/ortion ( ! magnetic l9es w occur z %[n 9 fig4 #bie4 ,! result+ me*anical actions are easily det]m9$ by rememb]+ t ! magnetic l9es act l ela/ic cords t5d+ to %ort5 !mselves4 ,!re is 9 fact a t5sion along ! magnetic l9es & a pressure at "r angles to bo?1 proportional at e po9t to ! squ>e ( _! d5sity4 ,illu/ration3 ,,fig4 #bie4--;,illu/rat+ drag on armature inductors4 ,9 mov+ a wire c>ry+ a curr5t ?r\gh a magnetic field1 ! l9es ( =ce are di/ort$1 & ! effect on ! wire is ! same z ?\gh ! magnetic l9es 7 ela/ic cords t5d+ to %ort5 !mselves4 ,!y1 !re=e1 oppose ! motion ( ! wire2 h5ce1 9 dynamo op]ation1 m or less p[] is absorb$ 9 ov]com+ ?is drag on ! num]\s inductors4 ,9 ! figure ! inductor is be+ mov$ upw>d aga9/ ! drag due to ! magnetic field4 ,x is evid5t by inspection ( ! l9es 9 fig4 #bie1 t !re is a drag ^u ! conductor 9 ! direction %[n by ! arr[4 ,smoo? & ,slott$ ,armatures4--,! inductors ( an armature may be plac$ on a smoo? drum or 9 slots cut 9 ! surface p>allel to ! axis4 ,9 ! fir/ in/ance1 ! magnetic drag comes on ! inductors & 9 ! case ( slots1 ^u ! tee?4 ,! effect ( emb$d+ ! armature inductors 9 slots is to di/ort ! magnetic field z %[n 9 fig4 #bif4 ,mo/ ( ! l9es ( =ce pass ?r\gh ! tee?1 ?us1 n only are ! inductors bett] plac$ = driv+ purposes1 b1 be+ scre5$ magnetically by ! tee?1 ! =ces act+ on !m are r$uc$1 ! great] "p ( ! magnetic drag be+ tak5 up by ! core4 ,x %\ld be not$ t1 al?\gh scre5$ f ! field1 ! inductors 9 a slott$ armature cut magnetic l9es precisely z if !y 7 n protect$4 ,! effect is z ?\gh ! magnetic l9es fla%$ across ! slots f too? to too?1 in/ead ( pass+ across ! int]m$iate slot at ! ord9>y angul> velocity4 ,comp>ison ( ,smoo? & ,slott$ ,armatures4--,! slott$ armature has ! foll[+ advantages ov] ! smoo? type3 #a4 ,r$uc$ reluctance ( ! air gap2 #b4 ,bett] protection = ! w9d+2 #c4 ,inductors held firmly 9 place prev5t+ slippage2 #d4 ,no magnetic drag on inductors2 #e4 ,no eddy curr5ts 9 inductors2 #f4 ,bett] v5tilation2 #g4 ,opposition to armature reaction4 ,due to increas$ d5sity ( flux ?r\gh ! tee?4 ,! disadvantages ( slott$ armatures may be /at$ z foll[s3 #a4 ,t5d5cy ( ! tee? to induce eddy curr5ts 9 ! pole pieces2 #b4 ,increas$ self-induction ( ! armature coils2 #c4 ,great] hy/]esis loss on acc\nt ( d5s] flux 9 ! tee?2 #d4 ,leakage ( l9es ( =ce ?r\gh ! core1 especially 9 ! case ( p>tially enclos$ slots4 ,illu/ration3 ,,fig4 #bif4--;,effect ( slott$ armature4 ,! tee?1 z !y sweep pa/ ! pole face1 cause oscillations ( ! magnetic flux 9 ! iron ne> ! surface because ! l9es 9 ! pole piece ,,pp t5d to cr[d t[>d ! ne>e/ tee?1 & w be less d5se opposite ! slots4 ,?is fluctuation ( ! magnetic l9es produce eddy curr5ts 9 ! pole faces unless lam9at$4 ,! armature inductors1 be+ scre5$ f ! field1 are reliev$ ( ! drag :i* is tak5 by ! tee?4 ,magnetic ,hy/]esis 9 ,armature ,cores4--,:5 ! direction or d5sity ( magnetic flux 9 a mass ( iron is rapidly *ang$ a consid]able exp5diture ( en]gy is requir$ :i* does n appe> z useful "w4 ,= in/ance1 :5 an armature rotates 9 a bipol> field1 ! armature core is subject$ to two opposite magnetic inductions 9 ea* revolution2 t is1 at any "o in/ant a nor? pole is induc$ 9 ! core opposite ! s\? pole ( ! magnet & a s\? pole 9 ! core opposite ! nor? pole ( ! magnet z indicat$ 9 fig4 #big by n & s4 ,accord+ly1 if ! armature rotate at a spe$ ( #a1jjj revolutions p] m9ute1 ! pol>ity ( ! armature w be *ang$ #b1jjj times p] m9ute1 & result 9 ! g5]ation ( heat at ! exp5se ( a portion ( ! en]gy requir$ to drive ! armature4 ,?is loss ( en]gy is due to ! "w requir$ to *ange ! position ( ! molecules ( ! iron1 & takes place bo? 9 ! process ( magnetiz+ & demagnetiz+2 ! magnetism 9 ea* case lagg+ beh9d ! =ce4 ,core ,loss or ,iron ,loss4--,^! t]ms are (t5 employ$ to designate ! total int]nal loss ( a dynamo due to ! comb9$ effect ( eddy curr5ts & hy/]esis1 b z ! losses due to ! =m] are gov]n$ by laws totally diff]5t f ^? applicable to ! latt]1 special analysis is requir$ to sep>ate !m4 ,! eddy curr5t loss p] p\nd ( iron 9 ! armature core dim9i%es ) ! ?9ness ( ! lam9at$ %eets1 & may be made indef9itely small by ! use ( indef9itely ?9 iron plates1 7 x n = c]ta9 me*anical & economical reasons4 ,! loss due to hy/]esis p] p\nd ( iron 9 ! core1 does n v>y ) ! ?9ness ( ! core plates2 x c be r$uc$ only by ! use ( a mat]ial hav+ a l[ hy/]etic coeffici5t4 ,dead ,turns4--,! voltage g5]at$ 9 a dynamo ) a giv5 degree ( field excitation is n /rictly proportional to ! spe$1 b some:at bel[ on acc\nt ( ! v>i\s reactions4 ,t is1 ! ma*9e acts z ?\gh "s ( its revolutions 7 n effective 9 induct+ electromotive =ce4 ,! "n dead turns is giv5 to ! numb] ( revolutions by :i* ! actual spe$ exce$s ! !oretical spe$ = any output4 ,aga91 ?is t]m is sometimes us$ to d5ote t portion ( ! wire on an armature :i* comes outside ! magnetic field & is !re=e r5d]$ ineffective 9 induc+ electromotive =ce4 ,! numb] ( dead turns is ab\t #bj ( ! total numb] ( turns4 ,illu/ration3 ,,fig4 #big4--,magnetic hy/]esis 9 armature core4 ,unlike poles are induc$ 9 ! core opposite ! poles ( ! field magnet4 ,s9ce on acc\nt ( ! rotation ( ! core ! induc$ poles are rev]s$ a ?\s& or m times a m9ute1 consid]able en]gy is requir$ to *ange ! positions ( ! molecules ( ! iron = ea* rev]sal1 result+ 9 ! g5]ation ( heat at ! exp5se ( a portion ( ! en]gy requir$ to drive ! armature4 ,self-induction 9 ! ,coils2 ,spuri\s ,resi/ance4--,self-induction opposes a rapid rise or fall ( an electric curr5t 9 j ! same way t ! in]tia ( matt] prev5ts any in/antane\s *ange 9 its motion4 ,?is effect is produc$ by ! action ( ! curr5t ^u itself dur+ v>iations 9 its /r5g?4 ,9 ! case ( a simple /raight wire1 ! ph5om5on is almo/ imp]ceptible1 b if ! wire be 9 ! =m ( a coil1 ! adjac5t turns act inductively ^u ea* o!r ^u ! pr9ciple ( ! mutual induction aris+ betwe5 two sep>ate adjac5t circuits4 ,ques4 ,:at effect has self-induction on ! op]ation ( a dynamo8 ,ans4 ,x prev5ts ! in/antane\s rev]sal ( ! curr5t 9 ! armature coils4 ,t is1 ! curr5t t5ds to g on & 9 fact does actually cont9ue = a brief "t aft] ! bru% has be5 rea*$4 ,illu/ration3 ,,fig4 #bih4--;,di/ribution ( magnetic l9es ?r\gh a r+ armature4 ,s9ce ! l9es foll[ ! metal ( ! r+ in/ead ( p5etrat+ ! int]ior1 no electromotive =ce is induc$ 9 t portion ( ! w9d+ ly+ on ! int]ior surface ( ! r+4 ,!re is1 !re=e1 a l>ge am\nt ( dead wire or wire t is ineffective 9 induc+ electromotive =ce2 ?is is ! *ief objection to ! r+ type ( armature4 ,ques4 ,:at becomes ( ! en]gy ( ! curr5t at rev]sal8 ,ans4 ,! en]gy ( ! curr5t 9 ! section ( ! w9d+ und]go+ commutation is wa/$ 9 heat+ ! wire dur+ ! int]val :5 x is %ort circuit$1 & z x passes on1 en]gy mu/ aga9 be sp5t 9 />t+ a curr5t 9 x 9 ! rev]se direction4 ,!re is1 !n1 a lagg+ ( ! curr5t 9 ! armature coils due to self-induction4 ,ques4 ,:at is spuri\s resi/ance8 ,ans4 ,?is is an app>5t increase ( resi/ance 9 ! armature w9d+1 :i* is proportional to ! spe$ ( ! armature1 & due to ! lagg+ ( ! curr5t4 ,illu/ration3 ,,fig4 #bii4--;,di/ribution ( magnetic l9es ?r\gh solid drum armature ( a f\r pole ma*9e4 ,armature ,losses4--,! me*anical p[] deliv]$ to ! pulley ( a dynamo is always 9 excess ( its electrical output on acc\nt ( num]\s me*anical & electrical losses4 ,me*anical losses result f3 #a4 ,friction ( be>+s2 #b4 ,friction ( commutator bru%es2 #c4 ,air friction4 ,! electrical losses may be classifi$ z ^? due to3 #a4 ,armature resi/ance2 #b4 ,hy/]esis2 #c4 ,eddy curr5ts4 ,ques4 ,h[ d ! me*anical & electrical losses comp>e8 ,ans4 ,! me*anical losses are small 9 comp>ison ) ! electrical losses4 ,ques4 ,:at may be said ) respect to friction8 ,ans4 ,! be>+ friction v>ies ) ! load4 ,9 calculat+ ?is loss n only mu/ ! weight ( ! armature be consid]$ b also ! belt t5sion & magnetic attraction 9 ord] to get ! resultant ?ru/ on ! be>+4 ,friction ( ! bru%es is v small & may be neglect$4 ,a small loss ( p[] is caus$ by ! friction ( ! air on ! armature4 ,! latt]1 s9ce x revolves rapidly1 acts to "s ext5t z a fan1 & 9 "s ma*9es ?is fan action is made use ( = v5tilation & cool+4 ,ques4 ,h[ are ! o!r losses det]m9$8 ,ans4 ,! loss ( p[] due to armature resi/ance is easily f\nd by ,ohm's law1 b ! hy/]esis & eddy curr5t losses1 kn[n collectively z iron losses1 are n s easily det]m9$4 ,if ! magnetization curve ( ! p>ticul> quality ( iron us$ = armature plates be kn[n1 ! hy/]esis loss may be calculat$ approximately4 ,eddy curr5t losses are ! mo/ important1 especially 9 l>ge ma*9es4 ,z previ\sly expla9$1 9 all ! mov+ metal masses unless lam9at$1 !re w be eddy curr5ts set up if !y cut magnetic l9es4 ,p[] may be lo/ f ?is cause ev5 9 ! metal ( ! %aft if !re be leakage ( magnetic l9es into x4 ,,*apt] ,,xx ,,commutation ,,& ,,! ,,commutator ,! act ( commutation ne$s special /udy4 ,if x be incorrectly p]=m$1 ! imp]fection at once manife/s itself by sp>ks :i* appe> at ! bru%es4 ,9 ! /udy ( ?is *apt] on commutation x w\ld be advisable = ! /ud5t to fir/ review ! basic pr9ciples ( commutation z giv5 9 *apt] ,,xiv1 :i* conta9s a brief & simple explanation ( h[ ! alt]nat+ curr5t 9 ! armature is conv]t$ into direct curr5t by ! action ( ! commutator4 ,ques4 ,:at is ! p]iod ( commutation8 ,ans4 ,! "t requir$ = commutation1 or ! angle ?r\gh :i* ! armature mu/ turn to commute ! curr5t 9 "o coil4 ,ques4 ,^u :at does ! p]iod ( commutation dep5d8 ,ans4 ,^u ! wid? ( ! bru%es z %[n 9 fig4 #cjj4 ,?is fixes ! angle ?r\gh :i* ! armature mu/ revolve to commute ! curr5t 9 "o coil4 ,?is angle is =m$1 z %[n 9 ! figure1 by two int]sect+ planes1 ,m & ,s1 :i* pass ?r\gh ! axis ( ! armature & ! two edges ( ! bru%4 ,commutation !n1 beg9s at ,m & ends at ,s4 ,ques4 ,:at is ! position ( ! commutat+ plane ) respect to ,m & ,s1 9 fig4 #cjj8 ,ans4 ,x bisects ! angle =m$ by ! planes ,m & ,s4 ,illu/ration3 ,,fig4 #cjj4--;,armature ) "o bru% 9 position to illu/rate ! p]iod ( commutation & commutat+ plane4 ,! latt] is call$ commutat+ l9e by "s writ]s4 ,! p]iod ( commutation dep5ds on ! ?ickness ( ! bru% end 9 contact ) ! commutator4 ,c>eful di/9ction %\ld be made betwe5 commutat+ plane1 neutral plane1 & normal neutral plane z def9$ else:]e4 ,ques4 ,:at is ! ! commutat+ plane8 ,ans4 ,an imag9>y plane pass+ ?r\gh ! axis ( ! armature & ! c5t] ( contact ( ! bru%4 ,ques4 ,:at two planes are ref]r$ to 9 /at+ ! position ( ! bru%es8 ,ans4 ,! normal neutral plane & ! commutat+ plane4 ,! angle int]cept$ by ^! two planes repres5ts ! lead1 ?us 9 /at+ t ! bru%es h a lead ( #f1 means t ! angle int]cept$ by ! normal neutral plane & ! commutat+ plane is #f4 ,illu/ration3 ,,fig4 #cja4--,! prop] position ( ! bru%es1 if !re 7 no field di/ortion & self-induction 9 ! armature coils1 w\ld be 9 ! normal neutral plane4 ,9 ! actual dynamo ^! two di/urb+ effects are pres5t :i* makes x necess>y to advance ! bru%es z %[n 9 figs4 #cjb & #cjc to secure sp>kless commutation4 ,ques4 ,:at is ! diff]5ce betwe5 ! normal neutral plane & ! neutral plane8 ,ans4 ,?is is illu/rat$ 9 figs4 #cja & #cjb4 ,! normal neutral plane is ! position ( z]o induction assum+ no di/ortion ( ! field z 9 fig4 #cja4 ,! neutral plane is ! position ( z]o induction ) di/ort$ field z 9 fig4 #cjb & z is f\nd 9 ! actual ma*9e2 ! di/ortion is exagg]at$ 9 ! figure = cle>ness4 ,illu/ration3 ,,fig4 #cjb4--;,bru% adju/m5t = field di/ortion4 ,! effect ( ! latt] is to twi/ ! l9es ( =ce ar\nd 9 ! direction ( rotation1 ?us maximum induction takes place 9 an incl9$ plane4 ,! bru%es !n mu/ be advanc$ to ! neutral plane :i* is at "r angles to ! plane ( maximum induction4 ,?is gives ! prop] position ( ! bru%es neglect+ self-induction4 ,ques4 ,:at is ! normal plane ( maximum induction8 ,ans4 ,a plane1 #ij 9 advance ( ! normal neutral plane1 be+ ! position ( maximum induction ) no di/ortion ( field1 z 9 fig4 #cja4 ,ques4 ,:at is ! plane ( maximum induction8 ,ans4 ,a plane #ij 9 advance ( ! neutral plane1 be+ ! position ( maximum induction 9 a di/ort$ field z 9 fig4 #cjb4 ,illu/ration3 ,,fig4 #cjc4--;,bru% adju/m5t = self-induction4 ,= conv5i5ce an electric curr5t is reg>d$ z hav+ weight & h5ce possess+ ! prop]ty ( in]tia4 ,! curr5t !n dur+ commutation _c be in/antly br\ght to re/ & />t$ 9 ! rev]se direction b ^! *anges mu/ be br\ght ab\t gradually by an oppos+ =ce4 ,h5ce by advanc+ ! bru%es beyond ! neutral plane z illu/rat$1 commutation takes place ) ! %ort circuit$ coil cutt+ ! l9es ( =ce s z to induce a curr5t 9 ! opposite direction2 ?is opposes ! motion ( ! curr5t 9 ! %ort circuit$ coil1 br+s x to re/ & />ts x 9 ! opposite direction1 ?us prev5t+ sp>ks4 ,figs4 #cja to #cjc %\ld be c>efully comp>$ & ?or\ghly und]/ood4 ,ques4 ,:at %\ld be not$ ) respect to ! diff]5t planes8 ,ans4 ,! commutat+ plane %\ld be c>efully di/+ui%$ f ! normal neutral plane & f ! neutral plane1 z %[n 9 fig4 #cjc4 ,commutation4--,9 ord] to und]/& j :at happ5s dur+ commutation1 a section ( a r+ armature may be us$ = illu/ration1 su* z %[n 9 fig4 #cjd4 ,"h ! coils ,a1 ,b1 ,c1 ,d1 ,e1 are connect$ to commutator segm5ts #a1 #b1 #c1 #d1 & ! positive bru% is %[n 9 contact ) two segm5ts #b & #c1 ! bru% be+ 9 ! neutral position4 ,curr5ts 9 ! coils on ea* side ( ! neutral l9e fl[ to ! bru% ?r\gh segm5ts #b & #c2 ! bru% !n is positive4 ,illu/ration3 ,,fig4 #cjd4--;,commutation4 ,?is takes place dur+ ! brief int]val 9 :i* any two segm5ts ( ! commutator are bridg$ by ! bru%4 ,! coil connect+ ) ! two segm5ts "u ! bru% is ?us %ort circuit$4 ,dur+ commutation ! curr5t 9 ! %ort circuit$ coil is br\ght to re/ & />t$ aga9 9 ! rev]se direction aga9/ ! opposition (f]$ by its s call$ in]tia1 or effect produc$ by self-induction4 ,n[1 z ! armature turns1 ! commutator segm5ts come successively into contact ) ! bru%4 ,9 ! figure1 segm5t #c is j leav+ ! bru% & #b is beg9n+ to pass "u x1 h5ce1 = an in/ant ! coil ,c is %ort circuit$4 ,ques4 ,9 fig4 #cjd1 :at are ! curr5t conditions8 ,ans4 ,previ\s to contact ) segm5t #b1 curr5t fl[$ 9 coil ,c 9 ! same direction z 9 coil ,b4 ,ques4 ,:at occurs :ile ! bru% is 9 contact ) segm5ts #b & #c8 ,ans4 ,dur+ ?is brief int]val1 ! curr5t 9 ,c is /opp$ & />t$ aga9 9 ! opposite direction4 ,simil>ly ea* coil ( ! armature z x passes ! bru% w be %ort circuit$ & h its curr5t rev]s$4 ,?is is kn[n z commutation4 ,ques4 ,:at is ! effect ( field di/ortion ) respect to commutation8 ,ans4 ,! neutral plane no long] co9cides ) ! normal neutral plane b is advanc$ 9 ! direction ( rotation ( ! armature z %[n 9 fig4 #cjb4 ,! reaction ( ! poles ,n' & ,s' ( ! armature field on ! poles ,s & ,n ( ! ma9 magnetic field t5ds to cr[d ! l9es ( =ce into ! upp] pole face ( ! s\? pole ( ! magnet1 & into ! l[] pole face ( ! nor? pole4 ,?is effect is due to ! /rong magnetic attraction betwe5 ! opposite poles ,s & ,n' & ,n & ,s'1 & ! equally /rong repulsion betwe5 l poles ,n & ,n' & ,s & ,s'4 ,h5ce1 ! plane ( maximum induction no long] co9cides ) ! normal plane ( maximum induction1 b is advanc$ 9 ! direction ( rotation1 dep5d+ ^u ! /r5g? ( ! armature curr5t1 be+ %ift$ =w>d = an increase ( curr5t1 & backw>d = a decrease ( curr5t4 ,?is di/ortion ( ! field & ! consequ5t %ift+ ( ! plane ( maximum induction naturally results 9 ! %ift+ ( ! neutral plane f ! v]tical position to ! incl9$ position z %[n4 ,position ( ! ,bru%es2 ,sp>k+4--,9 accordance ) ! laws ( electromagnetic induction1 if ! bipol> r+ armature %[n 9 fig4 #cja be rotat$ 9 ! direction indicat$ by ! arr[ ! armature curr5t ent]+ at ! bru% ,e w divide1 "o "p pass+ ?r\gh ! coils on ! "r half ( ! r+1 & ! o!r "p ?r\gh ! coils on ! left half ( ! r+1 to ! bru% ,f1 f :i* ! total curr5t w pass out1 urg$ by ! full value ( ! electromotive =ce induc$ 9 all ! coils on bo? halves ( ! r+4 ,illu/ration3 ,,figs4 #cje to #cjh--;,improp] bru% adju/m5t result+ 9 excessive sp>k+4 ,:5 ! bru%es are n advanc$ f> en\gh1 commutation takes place be=e ! %ort circuit$ coil rea*es ! neutral plane1 h5ce1 its motion is n *ang$ ) respect to ! magnetic field s z to induce a rev]se curr5t till aft] commutation4 ,!re is !n no oppos+ =ce1 dur+ commutation1 to /op & rev]se ! curr5t 9 ! %ort circuit$ coil1 & :5 ! bru% breaks contact ) segm5t #a1 z 9 fig4 #cjh1 ! mom5tum ( ! curr5t 9 coil ,f causes x to jump ! air gap f segm5t #a to segm5t #b & ! bru%1 aga9/ ! enorm\s resi/ance ( ! air1 ?us produc+ a sp>k ^: int5sity dep5ds on ! mom5tum ( ! curr5t 9 coil ,f4 ,sp>k+1 if all[$ to cont9ue1 w injure ! bru%es & commutator segm5ts4 ,aga91 if ! bru%es be plac$ at ! po9ts ,g & ,h1 ea* half ( a curr5t ent]+ at ,g1 w pass ?r\gh "o-half ( ! coils on ! left side & "o-half ( ! coils on ! "r side ( ! r+1 s t ea* half ( ! curr5t w be urg$ =w>d by an electromotive =ce equal to ! electromotive =ce t5d+ to =ce x back1 & !re=e1 no curr5t w pass 9 or out ?r\gh ! bru%es4 ,f ^! consid]ations x is obvi\s t ! prop] position = ! bru%es w\ld be 9 ! normal neutral plane1 7 x n = ! di/urb+ effects ( armature reaction & self induction ( ! curr5t4 ,ques4 ,%\ld ! bru%es ( a dynamo be plac$ 9 ! neutral plane8 ,ans4 ,no4 ,ques4 ,:y n8 ,ans4 ,! bru%es mu/ be advanc$ beyond ! neutral plane to prev5t sp>k+4 ,ques4 ,:at is ! cause ( sp>k+ at ! bru%es8 ,ans4 ,x is due to self-induction 9 ! coil und]go+ commutation4 ,ques4 ,expla9 ! effect ( self-induction 9 detail4 ,ans4 ,:5 commutation takes place ) ! bru%es 9 ! neutral plane z 9 fig4 #cjd1 !re w be no voltage induc$ 9 ! %ort circuit$ coil ,c4 ,! curr5t1 !re=e1 :i* fl[$ 9 coil ,c be=e x 0 %ort circuit$ w cease1 & z segm5t #c breaks contact ) ! bru%1 x w be ?r[n z a p]fectly idle coil ^u ! "r h& half ( ! r+ 9 :i* a curr5t is fl[+ t[>d ! bru%4 ,moreov]1 ! curr5t :i* 0 fl[+ ?r\gh ,d & #c directly to ! bru%1 mu/ sudd5ly trav]se ! long] pa? ?r\gh ! idle coil ,c4 ,n[1 on acc\nt ( self-induction1 ! curr5t acts 9 precisely ! same mann] z ?\gh x _h weight2 t is3 ,x _c be in/antly /opp$ or />t$4 ,illu/ration3 ,,figs4 #cji to #cac4--;,h[ sp>kless commutation is obta9$ by advanc+ ! bru%es beyond ! neutral plane2 commutation progressively %[n4 ,illu/ration3 ,,fig4 #cji4--;,commutation beg9s2 curr5t fl[s up bo? sides ( ! armature1 unit+ at ,s & fl[+ to ! bru% ?r\gh commutator segm5t #a z indicat$ by ! arr[4 ,illu/ration3 ,,fig4 #caj4--,segm5t #b has come into contact ) ! bru% & coil ,f1 9 :i* commutation is tak+ place1 is n[ %ort circuit$4 ,! curr5t n[ divides at ,m1 "p pass+ to ! bru% ?r\gh segm5t #b1 & "p ?r\gh coil ,f & segm5t #a4 ,al?\gh coil ,f is %ort circuit$ & hav+ pass$ ! neutral plane1 is cutt+ ! l9es ( =ce s z to induce a curr5t 9 ! opposite direction1 x /ill cont9ues to fl[ ) un*ang$ direction aga9/ ^! oppos+ conditions4 ,?is is due to self-induction 9 ! coil :i* resi/s any *ange j z ! mom5tum ( a heavy mov+ body1 su* z a tra9 ( c>s1 (f]s resi/ance to ! action ( ! brakes 9 ret>d+ & /opp+ its motion4 ,!re=e1 :5 segm5t #c leaves ! bru%1 ! curr5t w n in/antly *ange its pa? & fl[ ?r\gh ,c1 b w be urg$ by its mom5tum1 & jump ! air gap betwe5 ! bru% & segm5t #c1 ?us produc+ a sp>k4 ,illu/ration3 ,,fig4 #caa4--,segm5t #b has mov$ fur!r "u ! bru%1 & ! opposition (f]$ to ! =w>d fl[ ( ! curr5t 9 ! %ort circuit$ coil ,f by ! rev]se induction 9 ! magnetic field to ! "r ( ! neutral plane has f9ally br\ght ! curr5t 9 ,f to re/4 ,! curr5ts f ea* side ( ! armature n[ fl[ direct to ! bru% ?r\gh _! respective end segm5ts #a & #b4 ,illu/ration3 ,,fig4 #cab4--,segm5t #a is n[ almo/ out ( contact ) ! bru%4 ,a curr5t has n[ be5 />t$ 9 ! coil ,f 9 ! rev]se direction due to induction 9 ! magnetic field to ! "r ( ! neutral plane2 x fl[s to ! bru% ?r\gh segm5t #b4 ,! curr5t has n yet rea*$ its full /r5g? 9 ,f1 accord+ly1 "p ( ! curr5t com+ up f ! "r divides at ,s & fl[s to ! bru% ?r\gh segm5t #a4 ,illu/ration3 ,,fig4 #cac4--;,completion ( commutation 9 segm5ts #a & #b2 ! bru% is n[ 9 full contact ) segm5t #b1 ! curr5t 9 coil ,f has n[ rea*$ its full value1 h5ce ! curr5t fl[+ up f ! "r no long] divides at ,s b fl[s ?r\gh ,f & segm5t #b to ! bru%4 ,if ! curr5t 9 ,f _h n rea*$ its full value1 at ! in/ant segm5t #a left contact ) ! bru%1 x c\ld n imm$iately be made to fl[ at full spe$ any m ?an c\ld a locomotive h its spe$ in/antly *ang$4 ,?is1 z previ\sly expla9$1 is due to self-induction 9 ! coil or ! s call$ in]tia ( ! curr5t :i* opposes any sudd5 *ange 9 its rate ( fl[ or direction4 ,accord+ly t portion ( ! curr5t :i* 0 fl[+ up f ! "r & pass+ (f at ,s to ! bru% ?r\gh segm5t #a z 9 fig4 #cab1 w\ld1 :5 ?is pa? is sudd5ly cut (f z 9 fig4 #cac1 enc\nt] enorm\s opposition 9 coil ,f4 ,h5ce1 x w\ld mom5t>ily cont9ue to fl[ ?r\gh segm5t #a & jump ! air gap betwe5 ?is segm5t & ! bru%1 result+ 9 a m or less int5se sp>k dep5d+ on ! curr5t conditions 9 coil ,f4 ,ques4 ,h[ may ?is sp>k+ be prev5t$8 ,ans4 ,if ! bru%es be giv5 additional lead1 t is %ift$ fur!r to ! "r to "s position z ,n ,n1 fig4 #cjd1 coil ,c w n rema9 idle dur+ ! int]val x is %ort circuit$1 b w cut ! magnetic l9es 9 su* a way z to induce a curr5t 9 ! rev]se direction ?r\gh x4 ,"u ^! conditions1 :5 segm5t #c breaks contact ) ! bru%1 ! curr5t fl[+ ?r\gh ,d does n enc\nt] an idle coil1 b "o 9 :i* a curr5t is fl[+ 9 ! same direction1 h5ce1 ! t5d5cy to jump ! air gap & produce a sp>k is r$uc$2 ) prop] adju/m5t ( ! bru%es1 !re w be no sp>k+4 ,ques4 ,:at is ! objection to v ?9 bru%es8 ,ans4 ,"t mu/ be all[$ = rev]sal ( ! curr5t1 h5ce ! bru%es mu/ n be s ?9 z m]ely to bridge ! insulation betwe5 segm5ts4 ,ques4 ,:at is ! effect ( lead8 ,ans4 ,!re is usually mu* sp>k+ :5 ! lead is too small2 a little sp>k+ :5 too great1 & no sp>k+ :5 j "r4 ,if ! lead be excessive1 !re is a wa/e ( en]gy due to ! g5]ation ( a l>g] rev]se curr5t 9 ! %ort circuit$ coil ?an is necess>y4 ,fix$ ,position ( ,bru%es4--,! condition = sp>kless commutation is t ! curr5t 9 ! %ort circuit$ coil be r$uc$ to z]o1 & increas$ 9 ! opposite direction up to ! same value z t 9 ! next coil lead+4 ,if ! bru%es are to rema9 9 a fix$ position1 ?is condition w only be realiz$ at ! p>ticul> load = :i* ! bru%es are set4 ,?us1 if ! bru%es be set = ! av]age load1 ! rev]s+ field w n be correct = ei!r a weak] or /rong] load4 ,h5ce1 sp>kless commutation ) fix$ bru%es mu/ be due to "s o!r factor4 ,ques4 ,:at may be said ) respect to c>bon bru%es8 ,ans4 ,s9ce c>bon possesses a high resi/ance1 ! drop w v>y greatly ) ! contact area1 ?us affect+ a diff]5ce ( pot5tial 9 ! two segm5ts pass+ "u ! bru% & x is l>gely to ?is t sp>kless commutation is due4 ,ques4 ,:at is ! effect ( resi/ance on commutation8 ,ans4 ,9 fig4 #cjd dur+ commutation1 t is1 :ile ! bru% contacts ) any two segm5ts1 z #b & #c1 ! curr5ts com+ up ?r\gh ! w9d+ on ei!r side ( ! neutral plane are (f]$ two pa?s to ! bru%3 #a1 direct to bru% ?r\gh ! connect+ segm5t1 or #b1 across ! %ort circuit$ coil & adjac5t segm5t4 ,?us1 on ! "r side3 to bru% ?r\gh segm5t #c1 or across coil ,c & adjac5t segm5t #b4 ,! curr5t w take ! pa? ( lea/ resi/ance4 ,at ! beg9n+ ( commutation1 almo/ ! entire bru% area be+ 9 contact ) segm5t #c1 ! contact resi/ance ( ?is segm5t w be mu* less ?an = segm5t #b2 h5ce1 n only w ! curr5t at ! "r fl[ ?r\gh #c1 b also ! curr5t at ! left aft] fir/ trav]s+ ! %ort circuit$ coil4 ,z commutation progresses1 ! area ( contact ( #c decreases :ile t ( #b increases1 & ! respective resi/ances v>y 9 inv]se proportion4 ,likewise ! t5d5cy ( ! curr5t 9 ! left half ( ! w9d+ to take ! long] pa? ?r\gh coil ,c & segm5t #c to ! bru% gradually decreases1 becom+ z]o :5 ! two contact areas become equal4 ,dur+ ! second half ( ! p]iod ( commutation1 ! contact area ( segm5t #b becomes great] & ( #c1 less2 ?us ! resi/ance ( #b is l[]$1 & t ( #c increas$4 ,accord+ly1 all ( ! curr5t at ! left w fl[ ?r\gh segm5t #b1 & ! curr5t at ! "r w fl[ ?r\gh ,c & #b r ?an ?r\gh #c4 ,9 ?is way ! curr5t is rev]s$ 9 ,c1 &1 if ! bru% be broad en\gh to all[ a suffici5t "t int]val1 ! curr5t 9 ,c is built up to its full value be=e segm5t #c leaves ! bru%1 ?us secur+ sp>kless commutation4 ,?is contact resi/ance factor 9 sp>kless commutation is illu/rat$ 9 figs4 #cad to #cah1 x be+ assum$ t dur+ commutation1 ! bru% contact resi/ance is inv]sely proportional to ! area ( contact1 & t ! w9d+ is free ( resi/ance & inductance4 ,! curr5t is tak5 z #dj amp]es1 9 :i* case #bj amp]es w fl[ f ea* side ( ! w9d+ to ! bru%4 ,9 fig4 #cad ! in/ant be=e commutation beg9s all ! curr5t w fl[ ?r\gh segm5t ,a4 ,at ! end ( ! fir/ qu>t] ( ! p]iod ( commutation1 fig4 #cae1 #cj amp]es w fl[ f ! "r to bru% ?r\gh ,a1 & f ! left1 #aj amp]es ?r\gh ! %ort circuit$ coil via ,a & #aj amp]es ?r\gh ,b4 ,at ! end ( ! second qu>t] or half p]iod1 fig1 #caf1 ! curr5t ?r\gh ea* half ( ! w9d+ w fl[ to ! bru% ?r\gh ^! respective segm5ts4 ,at ! end ( ! ?ird qu>t]1 fig4 #cag1 ! curr5t f ! "r w divide1 #aj amp]es go+ ?r\gh ,a1 & #cj amp]es trav]s+ ! %ort circuit$ coil & out ?r\gh ,b4 ,! entire curr5t f ! left w fl[ ?r\gh segm5t ,b4 ,at ! end ( ! f\r? qu>t]1 fig4 #cah1 or completion ( ! p]iod ! curr5t f ea* half ( ! w9d+ w fl[ to ! bru% ?r\gh ,b4 ,illu/ration3 ,,figs4 #cad to #cah4--;,bru% contact resi/ance !ory ( commutation1 neglect+ self-induction & resi/ance 9 ! coils4 ,! total curr5t is assum$ to be #dj amp]es made up ( #bj amp]es fl[+ t[>d ! bru% f ! coils on ! "r & #bj amp]es f ! coils on ! left4 ,dur+ commutation1 t is1 ! int]val dur+ :i* ! bru% contacts ) any two adjac5t segm5ts ( ! commutator1 ! curr5t is assum$ to v>y directly z ! contact area4 ,illu/ration3 ,,fig4 #cad4--;,beg9n+ ( commutation2 segm5t ,a is entirely "u ! bru%1 & ,b is at ! initial po9t ( contact4 ,= ?is position ! curr5ts f bo? sides fl[ to ! bru% ?r\gh segm5t ,a4 ,illu/ration3 ,,fig4 #cae4--,"o-qu>t] p]iod ( commutation4 ,"o qu>t] ( ! bru% area is 9 contact ) ,b & ?ree qu>t]s 9 contact ) ,a2 h5ce1 #aj amp]es w fl[ ?r\gh ,b & #cj amp]es ?r\gh ,a4 ,illu/ration3 ,,fig4 #caf4--,second qu>t] ( commutation p]iod4 ,! bru% n[ contacts equally ) bo? segm5ts1 h5ce #bj amp]es w fl[ ?r\gh ea* segm5t4 ,illu/ration3 ,,fig4 #cag4--,?ird qu>t] ( commutation p]iod4 ,?ree qu>t]s ( ! bru% area is 9 contact ) segm5t ,b & "o qu>t] ) segm5t ,a2 accord+ly1 #cj amp]es w fl[ ?r\gh ,b & #aj amp]es ?r\gh ,a4 ,illu/ration3 ,,fig4 #cah4--;,completion ( commutation4 ,! bru% is 9 full contact ) segm5t ,b & at ! po9t ( break+ contact ) ,a1 h5ce ! entire curr5t f bo? sides or #dj amp]es w fl[ ?r\gh ,b4 ,illu/ration3 ,,figs4 #cai to #cbc4--;,bru% contact !ory ( commutation = case 9 :i* ! bru% cov]s two segm5ts ( ! commutator4 ,fig4 #cai beg9n+ ( commutation2 fig4 #cbj "o-qu>t] p]iod2 fig4 #cba1 "o-half p]iod2 fig4 #cbb1 ?ree-qu>t] p]iod2 fig4 #cbc completion ( commutation4 ,ques4 ,:at is ! effect ( increas+ ! degree ( contact ( ! bru%es8 ,ans4 ,x l5g!ns ! p]iod ( commutation1 & p]mits x to />t 9 "o coil be=e ! prec$+ coil has entirely pass$ ?r\gh ?is /age4 ,! effect ( *ang+ ! degree ( contact is %[n 9 figs4 #cai to #cbc1 9 :i* ! wid? ( ! bru% is made equal to t ( two segm5ts4 ,con/ruction ( ,commutators4--,! commutator = a clos$ coil armature consi/s ( a numb] ( segm5ts or ,l-%ap$ b>s ,c ( drop =g$ h>d drawn copp] assembl$ ar\nd a tubul> iron hub z %[n 9 figs4 #cbd & #cbe4 ,! b>s are held 9 position by ! nuts ,e1 & wa%]s ,f1 screw$ on ! ends ( ! tube ,d4 ,! b>s are insulat$ f ea* o!r & f ! wa%]s by mica z %[n by ! heavy l9es ,g1 & !y are also insulat$ f ! tube ei!r by a tube ( mica ,h1 or by a suffici5t air space4 ,! ends ( ! sections ( w9d+ are connect$ to ! v]tical portions ( ! b>s ,k1 by ins]tion 9 ! slots ,l1 :]e !y are securely held 9 place by means ( ! b9d+ screws1 :i* = great] security are sold]$ toge!r1 & may be releas$ f ! slots1 :5ev] necess>y1 by ! application ( a hot sold]+ iron4 ,illu/ration3 ,,figs4 #cbd & #cbe4--,side & end sectional views ( commutator %[+ con/ruction4 ,! p>ts are3 ,c1 segm5ts2 ,d1 tubul> iron hub2 ,e1 end nuts2 ,f1 clamps2 ,g1 insulation2 ,l1 ris] connection4 ,x is v important t all ! p>ts ( ! commutator %\ld be fitt$ toge!r p]fectly & screw$ up tightly1 9 ord] to prev5t loos5ess4 ,commutator segm5ts are (t5 made ) ! wa%]s ,e1 project+ beyond ! ends1 b su* con/ruction r$uces ! effective l5g? ( ! commutator1 !re=e ! "u cut =m ( b> is pref]able4 ,9 ! con/ruction ( commutators1 ! conditions ( op]ation require t !re be3 #a4 ,adequate insulation2 ,x is necess>y to h good insulation betwe5 ea* segm5t1 & a specially good insulation betwe5 ! segm5ts & ! hub or sleeve on :i* !y are m\nt$2 also betwe5 ! segm5ts & end clamps4 ,! insulat+ mat]ial mu/ n absorb moi/ure1 h5ce asbe/os1 pla/]1 or vulcaniz$ fibre are n us$4 ,! end insulat+ r+s are usually built up ( mica & %ellac1 m\ld$ :ile hot "u pressure to ! correct %ape4 ,illu/ration3 ,,fig4 #cbf4--;,front view ( ,we/]n ,electric ,commutator = b> w\nd armature4 ,?is commutator is made ( h>d drawn copp] & insulat$ ?r\gh\t1 v5tilat+ spaces be+ provid$ ne> ! %aft4 #b4 ,rigidity aga9/ c5trifugal =ce2 ,s9ce ! segm5ts are subject to c5trifugal =ce1 !y mu/ be securely clamp$ 9 place4 ,screws _c be us$1 = t w\ld de/roy ! insulation4 ,!y are !re=e held 9 place by insulat$ clamps z %[n 9 fig4 #cbd4 ,^! clamps %\ld be /rong & capable ( hold+ ! segm5ts firmly 9 position1 = if a segm5t %\ld rise out ( its place ?r\gh c5trifugal =ce1 x w\ld di/urb ! action ( ! bru% & cause sp>k+4 #c4 ,provision = we>4 ,! segm5ts %\ld be ( consid]able radial dep?1 s t ! commutator may be turn$ d[n f "t to "t to pres]ve its circul> =m4 ,illu/ration3 ,,fig4 #cbg4--,sectional view ( a ,g5]al ,electric commutator4 ,! segm5ts are ( roll$ or =g$ copp] & are sep>at$ by s(t mica insulat+ %eets4 ,?is mica mu/ we> d[n ev5ly ) ! copp]1 h5ce its consi/5cy is important4 ,! segm5ts are w$ge %ap$ s t :5 drawn radially inw>d !y support ea* o!r l ! /ones ( an ar*4 ,!y are drawn toge!r by holl[ cone coll>s :i* be> ^u lugs project+ f ! ends ( ! segm5ts4 ,^! lugs are turn$ to =m a smoo? cone aft] ! segm5ts are assembl$4 ,! coll>s are insulat$ ) mica f ! segm5ts & !y are held 9 place by nuts ^u ! commutator %ell or by bolts pass+ f end to end "u ! segm5ts4 ,! segm5ts are also provid$ ) lugs = connection to ! w9d+s4 ,po9ts ,relat+ to ,commutators4--#a4 ,! numb] ( commutator segm5ts dep5ds on ! s*eme ( w9d+ & on ! numb] ( sections 9 ! armature w9d+4 #b4 ,increas+ ! numb] ( b>s dim9i%es ! t5d5cy to sp>k1 & less5s ! fluctuations ( ! curr5t4 ,!re are two practical reasons = n us+ a v great numb] ( segm5ts3 x increases ! co/1 & 9 small ma*9es ! segm5ts w\ld be s ?9 t a bru% ( ! prop] ?ickness to collect ! curr5t w\ld lap ov]1 or bridge sev]al segm5ts4 ,types ( ,commutator4--,commutators are made 9 v>i\s =ms1 b !y may be gr\p$ into two g5]al types3 #a4 ,commutators = clos$ coil armatures2 ,^! consi/ ( a l>ge numb] ( segm5ts or b>s1 insulat$ f ea* o!r & v>y+ 9 numb] accord+ to ! s*eme ( armature w9d+1 & on ! numb] ( sections into :i* t w9d+ is gr\p$4 ,illu/ration3 ,,fig4 #cbh4--;,a l>ge curr5t l[ voltage bipol> dynamo built = electrolytic "w & "h %[n to illu/rate ! l>ge size commutator & bru%es necess>y to collect ! l>ge curr5t4 ,c>bon bru%es w\ld n be suitable = ?is class ( ma*9e because ev5 ) copp] bru%es1 ^: conductivity is mu* high] ?an c>bon1 ! commutator mu/ be ( consid]able size to give ! requir$ bru% contact area4 ,! contra/ betwe5 ! axial l5g?s ( ! armature & ! commutator is v m>k$4 ,! rock] con/ruction is ( ! ord9>y type1 & heavy flexible cables conduct ! curr5t f ! bru% hold]s to ! fix$ t]m9als4 ,! ma*9e "h illu/rat$ gives #caj amp]es at #g volts :5 runn+ at a spe$ ( #adjj ,r4 ,p4 ,m41 correspond+ to an output ( #b4ag kil[atts4 #b4 ,commutators = op5 coil armatures2 ,?is =m ( commutator is us$ on "s ma*9es design$ especially = arc light+1 su* z ! ,bru% & ,?ompson-,h\/on ma*9es4 ,!y consi/ ( a comp>atively small numb] ( segm5ts ea* ( :i* cov]s a wide angle1 & are sep>at$ f ea* o!r by air gaps4 #c4 ,! segm5ts %\ld be ( consid]able dep? to p]mit return+ occasionally s t _! circul> =m may be pres]v$2 #d4 ,! insulat+ mat]ial mu/ be su* t x w n absorb oil or moi/ure2 ,mica is be/ adapt$ = insulation1 b z !re are a great _m v>ieties1 diff]+ greatly 9 h>dness & o!r equalities1 x is important to select ! k9d t we>s at ! same rate z ! segm5ts4 ,if ! mica be too h>d1 ! we>+ ( ! segm5ts w leave x project+ & prev5t prop] contact ) ! bru%es2 aga91 if ! mica be too s(t1 x w result 9 furr[s or depressions betwe5 ! segm5ts into :i* copp] du/ w collect1 caus+ %ort circuits4 ,,*apt] ,,xxi ,,bru%es ,,& ,,! ,,bru% ,,ge> ,) respect to con/ruction1 bru%es may be broadly classifi$ z3 #a1 ^? made ( metal1 &2 #b1 ^? made ( c>bon4 ,!re are sev]al v>ieties ( metal bru%1 su* z3 #a4 ,gauze bru%es2 #b4 ,wire bru%es2 #c4 ,lam9at$ or /rip bru%es4 ,gauze ,bru%es4--,^! are v flexible & yield+1 _! use be+ att5d$ ) little we> ( ! commutator4 ,ques4 ,:at is ! con/ruction ( a gauze bru%8 ,ans4 ,a gauze bru% is made up ( a %eet ( copp] gauze1 fold$ sev]al times1 ) ! wires runn+ 9 an oblique direction1 s z to =m a solid flat /rip ( f to in* 9 ?ickness1 increas+ ) ! volume ( ! curr5t to be collect$4 ,ques4 ,:at is ! object ( fold+ ! gauze ) ! wires runn+ 9 oblique directions8 ,ans4 ,x is to prev5t ! ends ( ! bru% fray+ or ?read+ out1 :i* w\ld be ! case if ! gauze 7 fold$ up 9 any o!r mann]4 ,ques4 ,:at are ! features ( gauze bru%es8 ,ans4 ,!y make good contact1 b are q exp5sive4 ,!y may be set ei!r tang5tially or radially1 ! latt] pref]ably1 s9ce ! po9t ( contact rema9s ! same z ! bru%es we> away4 ,illu/ration3 ,,figs4 #cbi to #ccb4--,v>i\s =ms ( bru%4 ,fig4 #cbi gauze bru%2 fig4 #ccj lam9at$ or /rip bru%2 fig4 #cca /rip & wire bru% z us$ on ! e>ly ,edison ma*9es2 fig4 #ccb c>bon bru%4 ,c>bon is pref]r$ to copp] = bru%es on acc\nt ( ! r$uction ( sp>k+ secur$ by its use4 ,wire ,bru%es4--,?is class ( bru%1 :i* 0 ext5sively us$ be=e ! inv5tion ( ! gauze bru%1 is made up ( a bundle ( brass or copp] wires1 laid side by side & sold]$ toge!r at "o end4 ,s9ce wire bru%es are h>d] ?an ! gauze bru%1 !y are m liable to cut or score ! commutator1 & are also m tr\blesome to trim4 ,lam9at$ or ,/rip ,bru%es4--,^! probably repres5t ! simple/ =m ( bru%1 b are n ext5sively us$ ow+ to ! lack ( flexibility4 ,!y consi/ ( a numb] ( /rips ( copp] or brass1 laid "o ^u ! o!r & sold]$ at "o end1 z 9 fig4 #ccj4 ,illu/ration3 ,,fig4 #ccc4--;,g5]al ,electric bru% hold]4 ,! bru% hold] yoke consi/s ( a ca/ iron r+ ( elliptical section1 support$ f ! bracket ( ! end %ield 9 su* a mann] z to facilitate ! %ift+ ( ! bru%es4 ,x is provid$ ) a suitable h&le1 & may be fa/5$ 9 any position by means ( a ?umb nut on ! outside ( ! bracket4 ,x is s con/ruct$ t ! t5sion on ! individual bru% c be adju/$ )\t lift+ ! bru% f ! commutator & )\t ! use ( tools4 ,! bru% c be remov$ :ile ! ma*9e is runn+1 )\t mov+ ! hold] on ! /ud & )\t di/urb+ any o!r bru%4 ,removal ( ! bru%es = inspection c be accompli%$ )\t p]man5t *ange 9 ! adju/m5t ( ! t5sion ( ! bru% hold] spr+4 ,! connection betwe5 ! bru% & /ud is made ?r\gh a flexible copp] connection4 ,ques4 ,:at "n is g5]ally giv5 to /rip bru%es8 ,ans4 ,!y are commonly & errone\sly call$ tang5tial bru%es1 b !y are really bevel$ at ! end & set incl9$ to ! l9e ( tang5cy s t ! ends ( all ! %eets w make contact4 ,9 ! ,bru% & ,?omson-,h\/on arc dynamos1 9 :i* ! curr5t is limit$ to t5 amp]es1 ! bru%es consi/ ( a simple /rip ( flexible %eet copp]1 ! ends ( :i* are slit 9 a numb] ( places s z to insure contact at sev]al po9ts4 ,illu/ration3 ,,fig4 #ccd4--;,crock]-,:eel] bru% hold]4 ,! c>bon bru% ,b is firmly clamp$ 9 ! box ,c by two screws :i* be> on a %eet ( brass to protect ! c>bon f be+ brok5 by ! ends ( ! screws4 ,! box ,c is c>ri$ by f\r flexible spr+s ,s ,s1 "o at ea* corn] & =m$ ( h>d copp] leaves4 ,^! are fix$ at "o end to ! box & at ! o!r to ! solid base :i* is 9 "o piece ) ! spoke atta*$ to ! rock] r+4 ,an adju/+ screw passes ?r\gh appropriate lugs on ! box ,c & loosely ?r\gh ! head ,a ( a fix$ arm a4 ,betwe5 ! l[] surface ( a & ! upp] lug on ! box ,c is plac$ ! pressure spr+4 ,c>bon ,bru%es4--,:5 metallic bru%es are us$ ^u ! commutators ( high t5sion ma*9es1 !y frequ5tly give rise to excessive sp>k+ & also heat+ ( ! armature1 ! metallic du/ giv5 (f appe>+ to lodge betwe5 ! segm5ts ( ! commutator1 ?us p>tially %ort circuit+ ! armature4 ,to obviate ?is1 c>bon bru%es are ext5sively us$ 9 su* dynamos1 ?is mat]ial be+ f\nd v effectual 9 ! prev5tion ( sp>k+4 ,ques4 ,:at is ! usual =m ( c>bon bru%es8 ,ans4 ,!y are usually 9 ! =m ( oblong blocks4 ,illu/ration3 ,,fig4 #cce4--,p]spective views ( ,crock]-,:eel] bru% hold]4 ,?is hold] is ( ! p>allel type 9 :i* ! bru%es may be adju/$ )\t affect+ ! lead4 ,ea* bru% is held rigidly 9 its box & !re are no slid+ contacts 9 ! pa? ( ! curr5t4 ,! hold] is fur!r describ$ "u fig4 #ccd4 ,ques4 ,h[ are !y adju/$ on ! commutator8 ,ans4 ,!y are set butt end on ! commutator1 & f$ =w>d z !y we> away by means ( a spr+ hold]4 ,ques4 ,:y are c>bon bru%es s ext5sively us$8 ,ans4 ,because !y are ! only =m ( bru% t w give good commutation ) fix$ lead4 ,ques4 ,:at may be said ( ! diff]5t grades ( c>bon 9 use = bru%es8 ,ans4 ,! v s(t c>bon leaves a lay] ( graphitic matt] on ! commutator1 & at high voltages1 ?is may cause sp>k+2 su* grade ( c>bon %\ld only be us$ on l[ voltage ma*9es4 ,illu/ration3 ,,fig4 #ccf4--,we/]n ,electric box type bru% hold]4 ,! box :i* holds ! bru% is broa*$ to all[ ! bru% to slide freely1 b n loosely1 to & f ! commutator aga9/ :i* x is normally held by a lev] act+ directly ^u ! bru% head4 ,?is avoids ! possibility ( unev5 be>+ on ! commutator1 z ! bru%es are all[$ v slight lat]al or angul> motion4 ,! adju/m5t ( a bru% is also simplifi$ aft] x has be5 remov$ & !n replac$4 ,t5sion on ! bru% head is obta9$ by a special spr+ :i* ma9ta9s any giv5 t5sion = :i* x may be set4 ,an auxili>y flat /eel spr+ on ! l[] side ( ! lev] acts z a %ock absorb] betwe5 ! lev] & ! bru% head1 absorb+ all m9or vibrations caus$ by a worn commutator4 ,side contact betwe5 bru% & bru% hold] is n reli$ ^u to c>ry ! curr5t1 flexible copp] pigtails p]=m+ ?is function to ! exclusion ( slid+ contacts or t5sion spr+s1 9 ord] to r$uce ! bru% loss4 ,x is n necess>y to take ! bru% rigg+ ap>t or loos5 cable connections :5 x is desir$ ei!r to remove or rev]se ! bru%es to *ange ! direction ( armature rotation4 ,ques4 ,h[ are ! ends ( c>bon bru%es treat$ & :y8 ,ans4 ,!y are usually cov]$ at _! upp] "p ) a coat+ ( electro-deposit$ copp] to insure good contact ) ! hold]4 ,comp>ison ( ,copp] & ,c>bon ,bru%es4--,copp] bru%es t5d to te> & r\gh5 ! surface ( ! commutator1 :ile c>bon bru%es t5d to keep ! surface smoo?4 ,copp] causes m we> ( ! commutator ?an c>bon4 ,) c>bon bru%es1 ! armature may be run 9 ei!r direction4 ,! resi/ance ( c>bon be+ great] ?an copp]1 !re is less %ort circuit+ caus$ by c>bon p>ticles ?an by ^? ( copp]4 ,illu/ration3 ,,fig4 #ccg--,we/+h\se bru% hold]4 ,x is made ( brass1 ca/ 9 "o piece1 & ( /&>d slid+ type ) a %unt ( braid$ copp] wire directly connect$ to a clamp on ea* bru% & to ! solid portion ( ! hold]1 :]e x is held by a screw4 ,?is %unt relieves ! spr+ ( heavy curr5ts4 ,! hold] is s arrang$ z to be easily accessible = adju/m5t1 clean+ & r5ewal ( c>bons4 ,prop] t5sion is provid$ by spiral /rap spr+s s m\nt$ z to elim9ate friction & give uni=m pressure ov] a wide work+ range4 ,! spr+ t5sion is readily adju/$ by a simple rat*et arrangem5t4 ,ques4 ,:at is ! *ief m]it ( c>bon bru%es8 ,ans4 ,!y give less sp>k+ ?an o!r types4 ,ques4 ,h[ has ! con/ruction ( c>bon bru%es be5 v>i$8 ,ans4 ,s9ce1 = m9imum sp>k+1 x is only necess>y t ! bru% h high resi/ance 9 ! region ne> its edge1 attempts h be5 made to increase ! conductivity ( ! o!r portions by comb9+ ) ! c>bon1 copp] %eets or wires4 ,ques4 ,:at are ! objections to c>bon bru%es8 ,ans4 ,!y are easily brok5 & n be+ flexible1 vibration1 or any r\ghness ( ! commutator w cause bad contact4 ,illu/ration3 ,,fig4 #cch4--;,holz] ,cabot multiple bru% hold]4 ,ea* bru% is fa/5$ securely to a ma*9$ surface by "o or two ma*9e screws1 mak+ a positive contact4 ,sev]al /rips ( flexible copp] ( ample section to c>ry ! curr5t are int]pos$ betwe5 ! "p ( ! hold] c>ry+ ! bru% & ! portion clamp+ ! /ud1 no slid+ contact or spr+ be+ !re=e requir$ to c>ry any curr5t4 ,! bru%es are proportion$ = a c>ry+ capacity ( n m ?an #be amp]es p] squ>e in* ( bru% surface4 ,! bru% c be adju/$ to any degree ( t5sion dur+ ! op]ation ( ! ma*9e if necess>y4 ,ea* hold] is insulat$ 9 su* a mann] t no %ort circuit c occur if ! hold] be accid5tally tipp$ backw>d :ile ! op]ator is *ang+ a bru% or clean+ ! commutator dur+ a run4 ,ques4 ,= :at class ( ma*9e are c>bon bru%es specially adapt$8 ,ans4 ,= ma*9es furni%+ a small curr5t at high pressure4 ,:5 c>bon bru%es are us$1 x is desirable t ! curr5t be small1 because1 on acc\nt ( ! l[ conductivity ( ! c>bon1 m contact area is necess>y ?an ) copp] = equal curr5t transmission4 ,= fix$ lead & fluctuat+ curr5ts1 c>bon bru%es %\ld be us$4 ,ques4 ,= :at class ( ma*9e are copp] bru%es especially adapt$8 ,ans4 ,= ma*9es furni%+ l>ge curr5t at l[ pressure1 z 9 fig4 #cbh4 ,size ( ,bru%es4--,! numb] ( bru% sets dep5ds ^u ! numb] ( poles ( ! ma*9e1 b !re may be sev]al bru%es 9 ea* set4 ,x is usual1 except 9 ! smalle/ ma*9es1 to place at lea/ two bru%es exactly simil> side by side in/ead ( "o broad bru%1 ?us all[+ "o bru% to be remov$ = trimm+ or r5ewal :ile ! ma*9e is runn+4 ,moreov]1 bett] contact is secur$ by ?is sub-division1 because a slight elevation 9 ! commutator surface at "o po9t may slightly raise "o bru% ( a set at ea* revolution )\t mu* h>m1 :ile ) "o broad bru%1 ! entire bru% w\ld be lift$1 caus+ bad sp>k+4 ,ques4 ,:at det]m9es ! numb] ( bru%es 9 ea* set8 ,ans4 ,x dep5ds ^u ! curr5t capacity1 size ( ma*9e1 & judgm5t ( ! design]4 ,ques4 ,:at may be said ) respect to ! dim5sions ( ! bru%es8 ,ans4 ,no g5]al rule c be giv5 = bread? & ?ickness ( bru%4 ,! contact face mu/ cle>ly be wid] ?an ! ?ickness ( ! insulation betwe5 commutator segm5ts1 s9ce ! p]iod ( commutation mu/ la/ an appreciable int]val ( "t on acc\nt ( self-induction4 ,ques4 ,:at %\ld be ! m9imum wid? ( ! bru% contact face8 ,ans4 ,x may be tak5 z "o & "o-half times ! ?ickness ( ! commutator segm5ts4 ,ques4 ,h[ wide %\ld a c>bon bru% contact be8 ,ans4 ,! bru% %\ld be ?ick en\gh to cov] two & "o-half commutator segm5ts4 ,! ?ickness %\ld 9 no case be excessive on acc\nt ( ! loss due to heat+1 :i* results f ! diff]5ce ( pot5tial at ! =w>d & re> edge ( ! bru%4 ,illu/ration3 ,,fig4 #cci4--;,contact angle = ! diff]5t types ( bru%4 ,at ,a is %[n a bru% ) tang5tial contact1 & at ,b1 a s call$ tang5t bru%2 ! latt] is prop]ly call$ an incl9$ bru%4 ,%eet copp] bru%es are set tang5tially z at ,a1 & gauze bru%es incl9$ z at ,b4 ,c>bon bru%es are plac$ radially z at ,c :5 m\nt$ 9 box hold]s1 & incl9$ opposite to ! direction ( rotation :5 us$ ) reaction hold]s4 ,contact ,angle ( ,bru%4--,?is may be def9$ z ! angle :i* ! bru%es make ) ! commutat+ plane z %[n 9 fig4 #cci4 ,! sev]al k9ds ( bru%1 toge!r ) ! v>i$ conditions ( op]ation require diff]5t contact angles rang+ f z]o to #ij4 ,?us 9 ! figure1 a copp] /rip bru% may lie at #ij or tang5tially z at ,a4 ,wire or gauze bru%es %\ld make a m or less acute angle z at ,b1 9 ord] to pres5t ! end & n ! side ( ! bru% to ! commutator4 ,c>bon bru%es may be plac$ end on or radially z at ,c1 :i* is ! position almo/ univ]sally us$ 9 ! case ( traction or o!r rev]s+ motors4 ,sometimes ! c>bon bru% is incl9$ z at ,d1 9 ord] t ! revolv+ commutator may t5d to pu% ! bru% aga9/ its supports & ?us ensure bett] contact4 ,bru% ,contact4--,! relation betwe5 contact pressure1 contact resi/ance1 & friction ( bru%es v>ies greatly = diff]5t k9ds ( bru%4 ,copp] bru%es w c>ry f #aej to #bjj amp]es p] squ>e in* ( contact surface2 & c>bon bru%es f #dj to #gj amp]es p] squ>e in*4 ,! usual contact pressure is #a4be to #a4e p\nds p] squ>e in* = copp] bru%es1 & #a4e to #b p\nds p] squ>e in* = c>bon bru%es4 ,! rim velocities ( commutators v>y f #a1ejj to #b1ejj feet p] m9ute1 ! velocity usually increas+ ) ! size ( ! ma*9e4 ,illu/ration3 ,,fig4 #cdj4--;,bissell d\ble bru% hold]4 ,flexible cables c>ry ! curr5t betwe5 ! bru%es & hold]s4 ,?is hold] works equally well = =w>d or rev]se rotation4 ,two or m hold]s are us$ on ea* /ud except = ! two smalle/ frames4 ,! con/ruction p]mits ( adju/m5t or r5ewal ( bru% :ile ! ma*9e is 9 op]ation4 ,suffici5t contact area ( bru% is provid$ to p]mit runn+ on "o c>bon at ord9>y loads 9 case ! o!r become worn or inop]ative4 ,ques4 ,:at is ! drop 9 voltage at ! bru%es8 ,ans4 ,= c>bon bru%es x is ab\t ,o4#h to #a4j volt at ea* contact1 or #a4f to #b4j volts = ! two1 positive & negative1 contacts ( a ma*9e4 ,?is value is n mat]ially affect$ by plac+ a numb] ( bru%es 9 p>allel or by us+ sev]al sets1 z 9 ! case ( multipol> ma*9es1 z su* arrangem5t m]ely r$uces ! curr5t d5sity1 & s9ce ! contact resi/ance v>ies 9 ! inv]se ratio1 _! product rema9s ne>ly con/ant4 ,ques4 ,:at may be said ( ! friction ( ! bru%es8 ,ans4 ,! coeffici5t ( friction ( bru%es is ab\t 4#b to4#be = copp] & 4#c = c>bon4 ,illu/ration3 ,,fig4 #cda--,we/]n ,electric bru% ge>4 ,! bru% hold]s c>ry c>bon bru%es & are s design$ t ! bru%es may be firmly clamp$ 9 position & also be capable ( indep5d5t adju/m5t4 ,any bru% c be remov$ :ile ! ma*9e is 9 op]ation )\t di/urb+ ! o!rs & )\t mov+ ! hold] on ! /ud4 ,ques4 ,h[ _m watts are lo/ at ! bru%es8 ,ans4 ,! watt loss is equal to #a4f to #b4 volts = c>bon multipli$ by ! total curr5t c>ri$4 ,! watt lo/ on acc\nt ( friction may be calculat$ by ! =mula3 774#c #gdf7_/ccjjj7 7,p ,s7 watts lo/ by c>bon friction1 9 :i* ,p is ! total pressure 9 p\nds on ! commutator1 & ,s1 ! rim velocity ( ! commutator 9 feet p] m9ute4 ,! losses due to contact resi/ance & bru% friction are v liable to be greatly increas$ above ! values t may be obta9$ by ! prec$+ me?ods1 if ! commutator & bru%es are dirty & r\gh1 or n 9 good condition4 ,illu/ration3 ,,figs4 #cdb to #cde4--,v>i\s types ( bru% hold]4 ,fig4 #cdb1 arm or lev] type2 fig4 #cdc1 spr+ arm type2 fig4 #cdd1 box type2 fig4 #cde1 reaction type4 ,bru% ,hold]s4--,^! are devices employ$ to hold ! bru%es aga9/ ! commutator ) ! prop] pressure4 ,!y diff] consid]ably 9 v>i\s types ( ma*9e1 h5ce1 no g5]al rules c be giv5 ) respect to _! con/ruction or use1 b any bru% hold] mu/ fulfill ! foll[+ requirem5ts3 #a4 ,x mu/ hold ! bru% securely & at ! same "t fe$ x =w>d z x we>s away s z to ma9ta9 a prop] contact2 #b4 ,x mu/ hold ! bru% at ! prop] contact angle2 #c4 ,x mu/ be capable ( be+ rais$ f ! commutator1 & held out ( contact by "s =m ( cat*2 #d4 ,x mu/ be s con/ruct$ t ! bru% c be easily remov$ = clean+ or r5ewal2 #e4 ,! spr+ pressure mu/ be adju/able2 #f4 ,! bru% hold]s !mselves mu/ be c>ri$ on a rock] arm1 or rock] r+4 ,x is desirable t bru% hold]s be capable ( individual adju/m5t1 s t ea* may be set at its own po9t ( m9imum sp>k+4 ,a few =ms ( bru% hold] are illu/rat$ 9 figs4 #cdb to #cde4 ,! v>i\s k9ds ( bru% hold] may be divid$ into f\r types3 #a4 ,arm or lev] type2 #b4 ,spr+ arm type2 #c4 ,box type2 #d4 ,reaction type4 ,9 ! arm or lev] type ! bru% is firmly atta*$ to ! extremity ( a rigid arm capable ( movem5t ab\t ! bru% sp9dle1 except 9 s f> z x is re/ra9$ by a spr+ z 9 fig4 #cdb4 ,fig4 #cdc %[s a bru% hold] ( ! spr+ arm type4 ,! bru% is firmly atta*$ to ! extremity ( a spr+ arm1 ! o!r end ( :i* is secur$ to ! bru% sp9dle1 & :5 once adju/$ is n capable ( movem5t ab\t ! bru% sp9dle4 ,9 ! box type ( bru% hold] z illu/rat$ 9 fig4 #cdd1 ! bru% is free to move up & d[n 9 ! bru% box1 s f> z x is n re/ra9$ by a spr+ rigidly secur$ to ! arm :i* c>ries ! bru% box at its extremity4 ,illu/ration3 ,,fig4 #cdf4--;,=t ,wayne type ,,mpl dynamo2 view %[+ details ( armature1 commutator & bru% rigg+ ( l>ge ma*9e4 ,! lam9ations ( ! armature core are pun*$ f ?9 %eet /eel1 anneal$ & japann$4 ,spac+ ribs are built into ! core at prop] int]vals =m+ air passages = v5tilation4 ,9 addition1 !re are recesses 9 ! inside ( ! flanges :i* p]mit ! passage ( air f ! int]ior ar\nd ! ends ( ! core to ! op5+s 9 ! end flanges4 ,! armature coils are con/ruct$ ( r\nd or b> copp] on /&>d =ms4 ,! coils are laid 9 slots 9 ! surface ( ! core4 ,! commutator is con/ruct$ ( b>s ( h>d drawn copp] ( uni=m size & %ape1 support$ & clamp$ at ei!r end betwe5 bevel$ r+s & securely seat$ on ! commutator drum4 ,! drum is connect$ by radial arms to ! commutator sleeve :i* is m\nt$ & key$ on ! armature hub ext5sion4 ,fig4 #cde %[s ! reaction type ( bru% hold]1 9 :i* ! movem5t ( ! bru% is con/ra9$ 9 "o direction by ! surface ( a "p rigidly secur$ to ! bru% sp9dle1 & is fur!r con/ra9$ by a spr+ controll$ arm1 ! pressure ( :i* is capable ( ready adju/m5t4 ,among ! special =ms ( bru% hold] may be m5tion$ #a4 ,scissor type ( bru% hold]1 us$ = slip r+s1 & consi/+ ( two arms pivot$ toge!r l a pair ( scissors4 ,! l[] ends ( ! arms c>ry ! bru%es1 suitably m\nt$1 & ! upp] ends are drawn toge!r by a spr+1 :i* ?us ex]ts pressure on ! bru%es4 #b4 ,clock spr+ type ( bru% hold] 9 :i* ! necess>y contact pressure is appli$ to ! bru% by means ( a clock spr+1 :i*1 ) ! aid ( a rat*et may be w\nd up & adju/$ to any desir$ pressure4 ,illu/ration3 ,,fig4 #cdg4--,we/]n ,electric bru% hold]4 ,?is hold] consi/s ( a rugg$ iron ca/+1 elliptical 9 section1 & support$ f ! commutator end be>+ bracket 9 su* a mann] z to provide = ! %ift+ ( ! bru%es4 ,a h&le atta*$ to ! yoke aids 9 ?is %ift+ & a ?umb nut on ! outside holds ! :ole bru% ge> 9 ! desir$ position4 ,! bru% is f$ ?r\gh an accurately broa*$ slot by a spr+ :i* ma9ta9s uni=m pressure aga9/ ! commutator ?r\gh\t ! we>+ l5g? ( ! bru%4 ,! long lev] arm ( ! spr+ is suffici5tly flexible to take up any m9or vibrations ( ! bru%4 ,! t5sion ( ! bru% may be adju/$ )\t lift+ x f ! commutator or di/urb+ any ( ! o!r hold]s4 ,! bru%1 may be remov$ = inspection by ?r[+ ! spr+ out ( not*4 ,! bru% is connect$ to ! hold] by flexible copp] pig tails ( ample curr5t c>ry+ capacity4 ,ques4 ,h[ are bru% hold]s c>ri$8 ,ans4 ,!y are c>ri$ by a rock] arm = bipol>1 & by a rock] r+ = multipol> ma*9es1 :i* is m\nt$ ^u "o ( ! ma9 be>+s1 or ^u a support specially provid$ = x1 be+ pivot$ to revolve f ! same c5t] z ! %aft1 to p]mit %ift+ ! bru%es4 ,ques4 ,m5tion "o tr\ble sometimes enc\nt]$ ) bru% hold]s4 ,ans4 ,!re is sometimes tr\ble result+ f ! curr5t pass+ ?r\gh ! spr+ :i* heats x & de/roys its ela/icity4 ,illu/ration3 ,,fig4 #cdh4--,we/]n ,electric p>allel spr+ bru% hold] z us$ on ! l>g] ma*9es4 ,ques4 ,h[ may ?is be avoid$8 ,ans4 ,by insulat+ "o end ( ! spr+1 & c>ry+ ! entire curr5t directly f ! bru% itself to ! ma9 conductors by a flexible copp] /rip or cable firmly connect$ to bo?4 ,ques4 ,:at may be said ) respect to bru% con/ruction on ma*9es = electrolytic "w8 ,ans4 ,! collection ( l>ge curr5ts at l[ voltage1 g5]at$ by comp>atively small ma*9es1 requires c>eful design ( bru%es & bru% hold]s4 ,! commutator is long] ?an ! commutators on ma*9es ( equal capacity at high] voltages1 & z a rule ! commutator segm5ts are ?ick] & few] 9 numb]4 ,ea* bru% set is made up ( num]\s n>r[ bru%es r ?an two abnormally wide ones4 ,an example ( bru% & bru% ge> design$ to meet su* conditions is %[n 9 fig4 #cbh4 ,9 l>ge ma*9es = electrolytic "w1 x is n unusual to f9d ! curr5t divid$ betwe5 two wide commutators1 "o at ea* end ( ! armature1 ?us giv+ a long] axial be>+ surface = ! bru%es )\t inconv5i5tly l5g!n+ ! p9s ^u :i* ! sep>ate bru%es are ?read$4 ,multipol> ,bru% ,ge>4--,! bru% ge> :i* includes ! hold]s & c>ri] arm or r+1 becomes m complicat$ z ! numb] ( poles & magnitude ( ! curr5t is increas$4 ,9 ! e>ly days ( multipol> ma*9es1 s*emes ( armature w9d+ 7 devis$ su* t all ! necess>y cross connections 7 made inside ! ma*9e1 & ! numb] ( bru% hold]s r$uc$ to two & plac$ at an angul> di/ance ap>t dep5d+ ^u ! numb] ( poles4 ,su* w9d+s1 ?\gh possible1 are n us$ mu*1 *iefly on acc\nt ( _! complexity1 :i* n only increases ! dang] ( error 9 con/ruction1 b also makes repairs co/ly4 ,9 mod]n multipol> ma*9es1 su* complicat$ w9d+s are avoid$1 & ! sev]al sets ( bru%es are connect$ toge!r 9 two gr\ps1 positive & negative4 ,^! connections are c>efully design$ z "p ( ! bru% ge>4 ,ques4 ,h[ are ! bru%es held 9 l>ge multipol> dynamos8 ,ans4 ,!y are held at ! prop] po9ts ( commutation by arms (fset f a ca/ iron rock] r+1 :i* is itself support$ by brackets project+ f ! magnet yoke z %[n 9 fig4 #cdf4 ,ques4 ,:at provision is made = %ift+ ! r+ to adju/ ! lead8 ,ans4 ,! r+ is rotat$ by means ( a worm ge> & h& :eel4 ,,*apt] ,,xxii ,,armature ,,con/ruction ,! armature ( a dynamo has be5 def9$ z3 a collection ( coils ( wire w\nd ar\nd an iron core1 & s arrang$ t electric curr5ts are induc$ 9 ! wire :5 ! armature is rotat$ 9 a magnetic field4 ,f ! me*anical po9t ( view ! armature may be said to be made up ( ! foll[+ p>ts3 #a4 ,%aft2 #b4 ,core2 #c4 ,spid] 79 l>ge ma*9es72 #d4 ,w9d+2 #e4 ,commutator4 7broadly speak+74 ,( ! two types ( armature1 r+ & drum1 ! latt] is almo/ univ]sally us$1 h5ce ! examples ( con/ruction :i* foll[ w be conf9$ *iefly to ?is type4 ,%aft4--,a typical armature %aft is %[n 9 fig4 #cdi4 ,x is made ( /eel &1 except 9 ! small] ma*9es1 is ?ick] 9 ! middle ?an at ! ends = /iffness to )/& ! /rong magnetic side pull on ! core :5 ! latt] is slightly1 ne>] "o pole piece ?an ! o!r4 ,ques4 ,:at is ! object ( provid+ %\ld]s on ! %aft z 9 fig4 #cdi8 ,ans4 ,!y s]ve to keep ! armature 9 ! prop] position ) respect to ! be>+s4 ,ques4 ,h[ is ! %aft proportion$8 ,ans4 ,if x be proportion$ to secure ! prop] /iffness1 x w be f\nd ( ample size to resi/ ! twi/+ /ra94 ,illu/ration3 ,,fig4 #cdi4--,typical %aft = an armature4 ,! illu/ration %[s ! keyways = pulley armature & commutator4 ,9 ! small] sizes1 !re is usually a flange at ,a1 & ?reads at ,b & ,c = reta9+ nuts4 ,! %aft is subject also to b5d+ by ! weight ( ! armature1 by ! magnetic drag on its core1 & 9 belt driv5 ma*9es1 by ! lat]al drag ( ! pulley4 ,:5 runn+1 x is also subject$ to b5d+ /resses if ! armature be n prop]ly balanc$4 ,if ! be>+s d n give1 x is evid5t t all su* actions t5d to b5d ! %aft at def9ite po9ts4 ,core4--,9 ! small & m$ium size dynamos1 ! core is atta*$ direct to ! %aft4 ,!re are two k9ds ( core3 #a4 ,smoo?2 #b4 ,slott$4 ,ques4 ,:at may be said ( ! smoo? type ( core8 ,ans4 ,x has become obsolete1 except 9 special cases1 z = ma*9es us$ = electrolytic "w :]e a l>ge curr5t at l[ voltage is requir$4 ,ques4 ,:at is necess>y ) a smoo? core8 ,ans4 ,driv+ horns z lat] describ$4 ,illu/ration3 ,,fig4 #cej4--,lam9at$ smoo? core armature p>tly assembl$4 ,x consi/s ( num]\s discs ( ?9 %eet iron ?read$ on ! %aft & press$ toge!r by end plates4 ,! object ( ?is con/ruction is to prev5t eddy curr5ts4 ,ques4 ,:at is a slott$ core8 ,ans4 ,"o hav+ a s]ies ( p>allel slots1 simil> to ! spaces betwe5 ! tee? ( a ge> :eel1 & 9 :i* ! inductors are laid4 ,ques4 ,:at provision is made to avoid eddy curr5t 9 cores8 ,ans4 ,!y are lam9at$4 ,ques4 ,describe ?is me?od ( con/ruction4 ,ans4 ,! core is made ( /amp+s ( ?9 wr\ght iron or mild /eel4 ,! num]\s discs /amp$ f ! %eet metal are ?read$ on ! %aft z 9 fig4 #cej1 =m+ a practically solid metal mass4 ,illu/ration3 ,,fig4 #cea4--,sectional view ( lam9at$ smoo? core armature %[+ end plates1 flange & reta9+ nut4 ,a key is provid$ to prev5t rotation ( ! core ) respect to ! %aft4 ,ques4 ,h[ ?ick are ! discs8 ,ans4 ,! ?ickness ranges f 4#jad in* to 4#jbe in*1 correspond+ to #bg & #bb ,b & ,s gauge respectively1 #bg gauge be+ mo/ly us$4 ,ques4 ,h[ are ! discs held 9 place8 ,ans4 ,by two end plates press$ toge!r ei!r by l>ge nuts screw$ directly on ! %aft z 9 fig4 #cea1 or by bolts pass+ ?r\gh ! core f end to end1 z 9 fig4 #ceb1 holes be+ pun*$ 9 ! discs = ! purpose4 ,ques4 ,:at precaution is tak5 ) respect to ! core bolts8 ,ans4 ,!y are insulat$ f ! core by tubes & wa%]s ( mica or o!r insulat+ mat]ial4 ,illu/ration3 ,,fig4 #ceb4--,lam9at$ armature core ) ?r\gh reta9+ bolts4 ,9 ! l>g] sizes1 ^! bolts are us$ in/ead ( a nut ?read$ on ! %aft on acc\nt ( ! l>ge size ( ! latt]4 ,ques4 ,:at is ! con/ruction ( ! core end plates1 & :y8 ,ans4 ,! rims are bevel$ q ?9 to avoid eddy curr5ts4 ,ques4 ,h[ is ! core connect$ to ! %aft8 ,ans4 ,s9ce ! core has ! full torque ex]t$ ^u x by ! drag ( ! inductors1 x mu/ be firmly connect$ to ! %aft by means ( a key1 z %[n1 s t x may be positively driv54 ,core discs are /amp$ 9 "o piece up to ab\t #cj in*es 9 diamet]1 & = l>g] sizes !y are built up f sections z lat] describ$4 ,figs4 #cec & #ced %[ two =ms ( disc /amp$ 9 "o piece4 ,! fir/ illu/rates a solid disc1 & ! second a v5tilat$ disc 9 :i* m or less ( ! metal is cut away ne> ! c5t]1 ?us provid+ passages = ! circulation ( air :i* c>ries away "s ( ! heat g5]at$ 9 ! armature4 ,illu/ration3 ,,figs4 #cec & #ced4--,solid & v5tilat$ core discs4 ,9 fig4 #cec1 ! metal cut away ne> ! c5t] r$uces ! weight & provides passages = air circulation4 ,9 "s in/ances a =c$ circulation is secur$ by means ( a fan atta*$ to ! armature1 z %[n 9 fig4 #cff4 ,insulation ( ,core ,discs4--,:5 ! discs are /amp$ f v ?9 metal1 ! m]e exi/5ce ( a film ( oxide is suffici5t insulation4 ,x is usual1 h[ev]1 to apply a quick dry+ v>ni% t w give a h>d t\gh coat & n s(t5 ) heat or become brittle & crumble "u vibration4 ,! v>ni% may be appli$ ei!r by dipp+ or ) a japann+ ma*9e2 x mu/ be v ?91 & ! solv5t employ$ %\ld be a v volatile _s4 ,=ms ( ,armature ,tee?4--,! tee? /amp$ 9 ! core discs are made 9 v>i\s %apes1 dep5d+ l>gely on ! me?od ( secur+ ! inductors 9 ! slots aga9/ electromagnetic drag & c5trifugal =ce4 ,! tee? may be cut ) _! sides3 #a4 ,incl9$2 #b4 ,project+2 #c4 ,not*$4 ,ques4 ,:at may be said ( tee? ) incl9$ sides8 ,ans4 ,a too? ( ?is type is %[n 9 fig4 #cef1 be+ slightly n>r[] at ! root ?an at ! top1 ! result+ slot hav+ p>allel sides4 ,illu/ration3 ,,fig4 #cee4--,we/]n ,electric slott$ armature core4 ,! lam9ations are ( %eet /eel1 anneal$ & japann$4 ,!y are m\nt$ directly on ! %aft1 7except 9 ! l>ge sizes7 & held 9 place by sub/antial end plates4 ,ques4 ,:at are ! features ( ! project+ type ( too?8 ,ans4 ,! project+ type is %[n 9 figs4 #ceg & #ceh 9 :i* ! tops project2 ?is gives a l>g] core area ar\nd ! circumf]5ce ( ! armature :i* r$uces ! reluctance ( ! air gap1 & provides project+ surfaces = reta9+ ! inductors 9 ! slots by ! ins]tion ( w$ges4 ,ques4 ,:at is ! object ( cutt+ not*es 9 tee?8 ,ans4 ,!y are provid$ = ! ins]tion ( reta9+ w$ges1 z 9 fig4 #cfa2 ?is results 9 less area at ! top ( ! tee?4 ,ques4 ,h[ %\ld tee? be proportion$ to secure mo/ effici5t op]ation8 ,ans4 ,! wid? ( ! too? %\ld be ab\t equal to ! wid? ( ! slot m9us twice ! ?ickness ( ! slot insulation2 t is1 ! cross sectional area ( ! tee? %\ld be equal to t ( ! slots4 ,illu/ration3 ,,figs4 #cef to #cei4--,v>i\s =ms ( armature tee?2 fig4 #cef incl9$ type =m+ a slot ) p>allel sides2 figs4 #ceg & #ceh project+ type :i* provides a support = ! reta9+ w$ges2 fig4 #cei enclos$ type :i* =ms tunnels = ! inductors4 ,advantages & ,defects ( ,slott$ ,armatures4--,! slott$ armature1 sometimes call$ ! ,pac9otti armature1 aft] its inv5tor1 has ! foll[+ advantages ov] ! smoo? type3 #a4 ,! inductors are held m firmly 9 place to resi/ /resses due to electromagnetic drag & c5trifugal =ce2 #b4 ,! inductors are protect$ by ! tee? aga9/ me*anical injury2 #c4 ,less reluctance ( ! air gap2 #d4 ,! int]mitt5t induction due to ! pres5ce ( ! tee? prev5ts ! =mation ( eddy curr5ts4 #e4 ,:5 ! tee? are saturat$ !y oppose ! %ift+ ( ! l9es due to armature reaction4 ,illu/ration3 ,,figs4 #cfj & #cfa4--,project+ & not*$ tee?2 cross sections %[+ inductors & reta9+ w$ges 9 place4 ,! disadvantages ( slott$ armatures comp>$ ) ! smoo? type are3 #a4 ,great] hy/]esis loss1 caus$ by d5s] flux 9 ! tee?2 #b4 ,g5]ation ( eddy curr5ts 9 ! pol> faces :5 ! latt] are n ( lam9at$ con/ruction2 #c4 ,great] self-induction 9 ! armature coils2 #d4 ,con/ruction m exp5sive2 #e4 ,leakage ( magnetic l9es ?r\gh core1 ext]ior to w9d+4 ,! g5]ation ( eddy curr5ts 9 ! pol> faces may be ov]come by mak+ ! air gap at lea/ #ej p] c5t4 ( ! di/ance betwe5 ! tee?1 s t ! magnetic l9es c spread f ! corn]s ( ! tee?1 & become ne>ly uni=mly di/ribut$ ov] ! pol> faces4 ,magnetic leakage ?r\gh ! core may be r$uc$ by mak+ ! am\nt ( metal above ! inductors v small4 ,slott$ ,cores2 ,built ,up ,con/ruction4--,9 ! case ( l>ge dynamos1 ! core discs are built up 9 ord] to r$uce ! co/ ( con/ruction2 ! foll[+ p>ts are us$3 #a4 ,spid]2 #b4 ,core r+s split into sections4 ,illu/ration3 ,,figs4 #cfb & #cfc4--,side & end view ( built up armature core4 ,! %eet metal r+ sections conta9+ ! tee? are fa/5$ into dovetail not*es 9 ! spid] z %[n4 ,! lay]s ( r+ sections are plac$ s z to break jo9ts & are held by end clamps & ?r\gh bolts ,b4 ,di/ance pieces are ins]t$ at int]vals to provide v5tilat+ spaces ,d1 ,d1 ,d4 ,ques4 ,:at is ! approv$ me?od ( core con/ruction 9 l>ge armatures8 ,ans4 ,! core %\ld be ( ! built up con/ruction to avoid wa/e ( mat]ial 9 ! /amp+s4 ,ques4 ,describe ! con/ruction ( a built up core4 ,ans4 ,r+ sections /amp$1 f %eet metal are fa/5$ to a c5tral support or spid]1 :i* consi/s ( an iron hub ) radiat+ spokes & a rim ) provision = fa/5+ ! r+s4 ,! rim ( ! spid] is provid$ ) dovetail not*es into :i* fit simil>ly %ap$ int]nal projections on ! core segm5ts4 ,^! features are %[n 9 figs4 #cfb to #cfd4 ,ea* lay] ( core sections is plac$ on ! spid] s z to break jo9ts & ! core ?us =m$ is firmly held 9 place by end clamps z %[n4 ,! mann] ( fa/5+ ! r+s to ! spid] is an important po9t1 = x mu/ be done )\t r$uc+ ! effective cross section ( ! core 9 ord] n to *oke ! magnetic flux4 ,illu/ration3 ,,fig4 #cfd4--;,built up core ) f\r spoke spid]1 ea* spoke c>ry+ two dovetail not*es ,9 ?is con/ruction a little m air space is obta9$ = v5tilation ?an :]e a sep>ate spoke is provid$ = ea* not*4 ,9 ord] to secure a bett] fit & r$uce ! ma*9e "w1 ! spid] hub 9 l>ge ma*9es is sometimes cor$ ) enl>g$ section betwe5 ! out] be>+ surfaces1 & x is n unusual to f9d ^! surfaces turn$ to two diff]5t sizes z 9 fig4 #cfe1 to admit ( easi] erect+4 ,to avoid any tr\ble t may arise by unequal expansion1 ! rim ( ! spid] is n made cont9u\s1 b 9 sev]al sections z %[n 9 fig4 #cfd4 ,! rim "h consi/s ( f\r sections ea* ( :i* has two dovetail not*es4 ,by ?us divid+ ! rim into sections1 its weight is some:at r$uc$ & ! v5tilat+ spaces betwe5 ! sections increas$4 ,v5tilation4--,9 ! op]ation ( a dynamo m or less heat is g5]at$1 dep5d+ on ! load2 h5ce x is desirable t provision be made to c>ry (f "s ( ?is heat to prev5t excessive rise ( temp]ature4 ,illu/ration3 ,,fig4 #cfe4--;,hub & %aft design on l>ge ma*9es to r$uce ! ma*9e "w & facilitate erect+4 ,ques4 ,:y d armature cores heat8 ,ans4 ,!y heat f ^! causes3 eddy curr5ts1 hy/]esis1 & heat g5]at$ 9 ! inductors4 ,ques4 ,h[ is adequate v5tilation secur$8 ,ans4 ,! spid] is con/ruct$ ) z mu* op5 space z possible ?r\gh :i* air curr5ts may circulate4 ,! core is divid$ into sev]al sections ) int]v5+ air spaces ,d z %[n 9 fig4 #cfc1 ! discs be+ kept ap>t at ^! po9ts by di/ance pieces4 ,^! op5+s betwe5 ! discs are call$ v5tilat+ ducts2 !y are usually spac$ f #b to #d in*es ap>t4 ,illu/ration3 ,,fig4 #cff4--,we/]n ,electric b>rel w\nd armature1 hav+ a fan atta*$ at "o end to induce a circulation ( air = v5tilation4 ,ques4 ,:at o!r provision is sometimes made to secure v5tilation8 ,ans4 ,9 "s ma*9es a =c$ circulation ( air is secur$ by means ( a fan atta*$ to "o end ( ! armature z %[n 9 fig4 #cff4 ,insulation ( ,core4--,be=e ! w9d+ is assembl$ on ! core1 ! latt] %\ld be ?or\ghly insulat$4 ,japan or enamel insulation is n suffici5t because x is liable to h bubbles or m9ute holes 9 x1 or be pi]c$ by p>ticles ( metal or by ! r\gh edges ( ! core discs4 ,two or m lay]s ( /rong pap]1 fibre1 canvas or mica1 %\ld be appli$ to ! core be=e plac+ ! inductors 9 position4 ,! ends ( ! core %\ld be insulat$ ) ?ick] mat]ial1 s9ce ! /ra9 ^u x is great]1 especially at ! edges4 ,illu/ration3 ,,fig4 #cfg4--;,holz] ,cabot p>tially w\nd b>rel w\nd armature %[+ arrangem5t ( coils4 ,! core is built up ( ?9 discs ( s(t anneal$ /eel1 :i* are slott$ to all[ ! wire to s9k bel[ ! surface1 ?is be+ sometimes call$ iron clad con/ruction4 ,! discs are held by end plates1 clamp$ )\t ?r\gh bolts4 ,! coils are ma*9e =m$ ( r\nd ribbon or b> copp] dep5d+ on ! size & purpose ( ! ma*9e1 be+ )\t jo9t except at ! commutator4 ,!y lie 9 insulat$ tr\ghs1 ! upp] lay]s be+ insulat$ f ! l[] lay]s by fibre4 ,armature ,w9d+s4--,! subject ( w9d+s has be5 fully treat$ f ! !oretical po9t ( view 9 *apt] ,,xviii4 ,x rema9s !n to expla9 ! diff]5t me?ods employ$ 9 ! %op & ! me*anical devices us$ to con/ruct ! s*eme ( w9d+ adopt$4 ,ques4 ,:at is ! con/ruction ( ! inductors8 ,ans4 ,!y are made ( copp]2 ! ord9>y =m consi/s ( simple copp] wire1 insulat$ ) a d\ble or triple cov]+ ( cotton1 & 9 "s cases copp] b>s are us$ = l>ge curr5t ma*9es4 ,ques4 ,:at is ! objection to copp] b>s8 ,ans4 ,!y are liable to h eddy curr5ts set up 9 !m z illu/rat$ 9 fig4 #bia4 ,illu/ration3 ,,fig4 #cfh4--;,holz] ,cabot iron clad b& w\nd armature complete2 view %[+ op5+s = v5tilation4 ,! advantage ( ! =m ( w9d+ adopt$1 is ! ease ) :i* a coil may be replac$ 9 case ( injury & ! additional cool+ surface4 ,! coils are held 9 place by maple w$ges secur$ by b9d+ wires :i* are sold]$ ?r\gh\t _! l5g?4 ,ques4 ,:at may be said ) respect to ! sizes ( wire us$ = inductors8 ,ans4 ,wire l>g] ?an ab\t numb] #h ,b & ,s gauge 74#abhe in* diamet]7 is n easily h&l$1 h5ce = l>ge inductors1 two or m wires may be w\nd toge!r 9 p>allel4 ,accord+ to ! me*anical features & mann] ( assembl+ on ! core1 drum w9d+s may be divid$ into sev]al classes1 z foll[s3 #a4 ,h& w9d+2 #b4 ,evolute or butt]fly w9d+2 #c4 ,b>rel w9d+2 #d4 ,ba/>d w9d+2 #e4 ,=m] w9d+4 ,h& ,w9d+4--,! fir/ w9d+s 7 put on by h& & prov$ objectionable on acc\nt ( ! clumsy ov]lapp+ ( ! wires at ! ends ( ! armature1 :i* /ops v5tilation & h9d]s repairs1 :ile ! out] lay]s ov]ly+ ^? fir/ w\nd1 br+ into close proximity inductors ( widely v>y+ voltage4 ,! me?od is /ill us$ 9 special cases & = small ma*9es4 ,su* a w9d+ has r>ely1 if ev]1 be5 made ) "o cont9u\s wire4 ,illu/ration3 ,,figs4 #cfi & #cgj4--;,evolute & /raight out connectors4 ,9 small ma*9es ! connectors mu/ be curv$ z 9 fig4 #cfi1 b 9 l>ge ma*9es1 especially :]e ! tee? are wide1 !y may be /raight z 9 fig4 #cgj4 ,^! connectors may take ei!r ( ! foll[+ =ms3 #a4 involute or evolute connectors--,an involute is ! curve drawn by ! extremity ( a piece ( /r+ :i* is unw\nd f a cyl9d]2 #b4 spiral connectors--,^! consi/ ( d\ble spirals1 ! commutator be+ usually connect$ to ! junction ( ! two spirals4 ,^! connectors are also kn[n z butt]fly connectors4 ,evolute or ,butt]fly ,w9d+4--,?is mode ( w9d+1 0 introduc$ by ,siem5s = electroplat+ dynamos to ov]come ! objections to h& w9d+4 ,x takes its "n f ! me?od ( unit+ ! inductors by means ( spiral end connectors z %[n 9 fig4 #cgd1 also 9 figs4 #cfi & #cgj1 :i* %[ m mod]n =ms4 ,illu/ration3 ,,fig4 #cga4--;,holz] ,cabot armature2 re> view %[+ back head & coil gu>d4 ,! con/ruction ( core & w9d+ is describ$ 9 fig4 #cfg4 ,! %aft is ( crucible /eel gr\nd to gauge4 ,! commutator segm5ts are ( drop =g$ copp] 9 ! small] & h>d-drawn copp] 9 ! l>g] sizes4 ,! insulat+ mat]ial betwe5 ! segm5ts is mica4 ,on ! l>g] sizes1 ! commutator %ell is fitt$ ) a ?read & m\nt$ on a spid]4 ,?is con/ruction provides op5+s betwe5 ! commutator & %aft = v5tilation4 ,ques4 ,:at are evolute connectors8 ,ans4 ,! =k %ap$ /rips us$ to connect b>s at diff]5t positions on ! armature1 z %[n 9 fig4 #cfi4 ,9 l>ge ma*9es1 especially :]e ! tee? are wide1 ^! connections may be /raight1 b 9 small cc ma*9es !y mu/ be curv$ 9 ! mann] %[n 9 ! upp] "p ( ! figure1 z ! room available may dim9i% by z mu* z half1 z ! l[e/ po9t is rea*$1 & ! room occupi$ by ! /rip is ! wid? ( a horizontal section at v>i\s po9ts4 ,?is wid?1 9 ! case ( ! /raight connections1 is con/ant4 ,9 place ( ! wood5 block1 us$ 9 e>ly ma*9es1 = fa/5+ ! middle "p ( ! connectors1 !y may be an*or$ to an insulat$ clamp+ device built up l a commutator & = t reason call$ a false commutator4 ,illu/ration3 ,,figs4 #cgb & #cgc4--;,b>rel & evolute w9d+s2 end views %[+ placem5t ( coils4 ,:5 all ! coils are w\nd on ! =m]1 ! plac+ ( !m on ! armature is a simple matt]4 ,aft] insulat+ ! slots1 ! w9d] beg9s at any conv5i5t slot1 & ins]ts ! coils z %[n4 ,be=e he c fill all ! slots1 "s ( ! fir/ coils mu/ be rais$ & ! la/ ones ins]t$ und]nea?4 ,!re is n mu* diff]5ce betwe5 b>rel & evolute w9d+ & "o /yle may be us$ at "o end ( ! armature & ! o!r at ! opposite end4 ,ques4 ,h[ are ! inductors arrang$ 9 evolute w9d+8 ,ans4 ,9 fig4 #cgc1 x w be se5 t ! ends ( ! evolute connectors lie 9 two planes1 h5ce ! inductors mu/ project to diff]5t di/ances beyond ! core4 ,accord+ly1 "o long & "o %ort b> may be conv5i5tly plac$ 9 ea* slot1 side by side4 ,9 l>ge ma*9es1 especially :]e ! tee? are wide1 ! connectors may be /raight z 9 fig1 #cgj4 ,evolute connectors may be us$ = ei!r lap or wave w9d+s4 ,illu/ration3 ,,fig4 #cgd4--,siem5s' b> armature2 end view4 ,ea* inductor 9 ! =m ( a b> is connect$ to ! next by means ( two evolute spiral copp] /rips1 "o b5d+ inw>dly1 ! o!r outw>dly1 _! junction be+ 9 "s cases secur$ to a block ( wood ^u ! %aft4 ,_! out] ends are atta*$ to ! b>s by rivets or silv] sold]4 ,b>rel ,w9d+4--,?is is a =m ( drum w9d+ 9 :i* ! inductors are arrang$ 9 two lay]s & c>ri$ out obliquely on an ext5sion ( ! cyl9drical surface ( ! drum to meet & connect ) radial ris]s4 ,illu/ration3 ,,figs4 #cge & #cgf4--,s+le lay] & d\ble lay] b>rel w9d+4 ,b>rel w9d+ is a me?od ( arrang+ ! ends ( armature coils z !y pass f "o pole to ! next1 9 :i*1 in/ead ( us+ involute or butt]fly connections1 ,v-%ap$ end connections are us$ :i* lie on a cyl9drical surface1 :i* is a cont9uation ( ! armature surface4 ,! coil ends mu/ ( necessity be arrang$ 9 two lay]s1 b ! me?od may be us$ = ei!r "o or two coils p] slot1 ! diff]5ce 9 arrangem5t = ^! is "h illu/rat$4 ,b>rel w9d+ has be5 v widely adopt$4 ,al?\gh x involves an increas$ l5g? ( armature1 ?is gives additional cool+ surface & provides = good v5tilation4 ,9 b>rel w9d+1 ! coil ends mu/ ( necessity be arrang$ 9 two lay]s b ! me?od may be us$ = ei!r "o or two coils p] slot1 ! diff]5ce 9 arrangem5t = ^! two cases be+ %[n 9 figs4 #cge & #cgf4 ,9 ! s+le lay] b>rel w9d+1 fig4 #cge1 ea* slot is occupi$ by b "o side ( "o coil4 ,9 ! d\ble lay] b>rel w9d+1 fig4 #cgf1 ! opposite sides ( two sep>ate coils occupy space 9 ! same slot4 ,! coils1 on em]g+ f ! slots b5d 9 opposite directions1 & if "o side ( a coil occupy ! bottom portion ( a slot1 its o!r side usually occupies ! top portion ( a slot di/ant f ! fir/ slot by ! pol> pit*4 ,illu/ration3 ,,fig4 #cgg4--,we/+h\se b>rel w\nd armature4 ,! coils are =m] w\nd f copp] /rap & are int]*angeable4 ,9 ! l>g] size ma*9e !y are ( ! s+le type4 ,! illu/ration %[s pla9ly ! *>act]i/ic feature ( b>rel w9d+1 namely ! oblique end connectors c>ri$ out on ! ext5d$ drum4 ,ba/>d ,w9d+4--,9 ?is type ( w9d+1 ! end connectors project f ! inductors 9 /raight l9es p>allel to ! %aft & !n are b5t inw>d4 ,x has ! effect ( be+ some:at %ort] ?an ! b>rel w9d+4 ,9 ord] to secure bett] v5tilation1 x is usual to comb9e a ba/>d w9d+ at ! re> end ( ! armature ) a b>rel w9d+ at ! commutator end4 ,?is class ( w9d+ is us$ only ) b> armatures4 ,illu/ration3 ,,fig4 #cgh4--,re> end ( ,we/+h\se wave-b>rel w\nd armature2 view %[+ v5tilation4 ,=m] ,w9d+4--,?is relates to a me?od ( w9d+ coils1 & n to any p>ticul> type2 t is1 me*anical w9d+ z di/+ui%$ f h& w9d+4 ,:ile h& w9d+ is necess>y = r+ armatures1 a drum armature is w\nd bett] & m easily by ! aid ( ma*9]y4 ,ques4 ,:at is a =m] coil8 ,ans4 ,a =m] coil1 z its "n sugge/s1 is "o t is w\nd complete ^u a =m] be=e be+ plac$ ^u ! armature4 ,ques4 ,:at is ! advantage ( ?is me?od ( w9d+ coils8 ,ans4 ,by ! use ( =m]s mu* "t is sav$1 ?us r$uc+ ! co/1 & also by _! use all ! coils are symmetrical :i* improves ! appe>ance ( ! f9i%$ w9d+4 ,illu/ration3 ,,figs4 #cgi & #chj4--;,diagrams illu/rat+ lap & wave b>rel w9d+s4 ,ques4 ,h[ is ! requir$ %ape ( ! template or =m] = w9d+ ! coils det]m9$8 ,ans4 ,by w9d+ "o coil on ! armature 9 ord] to asc]ta9 its dim5sions & %ape2 x is !n remov$ f ! armature & us$ z a patt]n 9 con/ruct+ ! =m]4 ,types ( ,=m] ,coil4--,( ! num]\s %apes ( =m] coil1 m5tion %\ld be made (3 #a4 ,evolute coils2 #b4 ,/raight out coil ,ques4 ,describe ! evolute type ( =m] coil4 ,ans4 ,! evolute coil is w\nd ar\nd eight p9s ins]t$ 9 a bo>d z %[n 9 fig4 #cha4 ,! requir$ numb] ( turns are tak5 ar\nd ^! p9s & _! ends ,g & ,h left project+4 ,! coil ?us =m$ is n[ cov]$ ) tape & aft] removal f ! bo>d1 is put into a clamp at ,c & ,f1 & op5$ up z %[n 9 fig4 #chb1 :i* is ! =m requir$ = ins]tion 9 ! prop] slots ( ! armature4 ,illu/ration3 ,fig4 #cha4--,me?od ( w9d+ evolute coils4 ,9 prep>+ ! =m]1 x is necess>y to "k ! dim5sions ( ! coil1 h5ce1 a patt]n coil mu/ fir/ be made1 f :i* ! spac+ ( ! p9s c be tak5 s t ! complet$ coil w fit into ! slots = :i* x is int5d$4 ,aft] ! p9s h be5 prop]ly spac$ on ! bo>d1 ! wire is w\nd ar\nd !m z indicat$1 z _m turns be+ tak5 z decid$ on = ea* coil4 ,:5 ! coil is ?us completely w\nd1 x is tak5 f ! p9s1 & ! l[] ends1 ,c & ,f1 plac$ 9 a suitable clamp4 ,! two halves ( ! coil are !n spread ap>t1 ! coil assum+ ! %ape illu/rat$ 9 fig4 #chb4 ,fig4 #chb4--;,appe>ance ( an evolute =m] w\nd coil op5$ out4 ,! po9ts ,a1 ,b1 ,c1 etc41 correspond to simil> po9ts 9 fig4 #cha4 ,ques4 ,:at is ! peculi>ity ( ! evolute coil8 ,ans4 ,! two sides ( ! evolute coil h unequal dim5sions4 ,! "p m>k$ ,,ab1 9 fig4 #cha :i* is an upp] lay] inductor is long] ?an ! "p ,,de1 :i* con/itutes a l[] lay] inductor4 ,! portions ,,dc & ,,ef act z p>ts ( an inn] lay] ( evolutes1 & ! portions ,,af & ,,bc z p>ts ( an out] lay] ( evolutes4 ,^! features are %[n 9 fig4 #chb4 ,ques4 ,h[ are evolute coils plac$ on ! core8 ,ans4 ,!y are plac$ 9 position z %[n 9 figs4 #cgb & #cgc1 cont9u+ ar\nd ! core until all ! slots are fill$4 ,to complete ! op]ation x is necess>y to raise "s ( ! fir/ laid coils & ins]t ! la/ ones bel[ !m4 ,! w9d+ is ?us complet$ & is symmetrical4 ,illu/ration3 ,,fig4 #chc4--,we/+h\se comb9ation ba/>d & b>rel w9d+4 ,a ba/>d w9d+ at ! re> end is comb9$ ) a b>rel w9d+ at ! commutator end1 z %[n 9 ! illu/ration1 to secure bett] v5tilation4 ,ques4 ,describe ! me?od ( w9d+ ! /raight out type ( =m] coil4 ,ans4 ,! /raight out coil may be w\nd on a =m] su* z %[n 9 fig4 #chd4 ,?is consi/s ( a bo>d hav+ f\r upright p9s1 ,a1 ,b1 ,d1 ,e1 prop]ly spac$ & two horizontal p9s ,c1 ,f1 atta*$ to ext5sions at ea* end ( ! bo>d4 ,a coil ( ! requir$ numb] ( turns is w\nd ar\nd ^! p9s & !n op5$ out z 9 fig4 #che4 ,aft] v>ni%+ & bak+ x is ready to be plac$ on ! armature4 ,ques4 ,= :at class ( w9d+ are /raight out =m] coils suitable8 ,ans4 ,= b>rel w9d+4 ,illu/ration3 ,,fig4 #chd4--,me?od ( w9d+ /raight out coils4 ,!re are sev]al ways ( mak+ ^! coils4 ,a =m] may be prep>$1 z %[n 9 ! figure1 ) a bo>d hav+ ins]t$ f\r p9s1 & hav+ atta*$ two blocks at ! ends c>ry+ horizontal p9s z %[n4 ,ar\nd ! sev]al p9s1 ! coil is w\nd to ! requir$ numb] ( turns & tap$4 ,?is coil diff]s f ! evolute coil 9 t ! two halves are ( equal size1 ! p>ts :i* act respectively z upp] & "u inductor be+ ( equal l5g?4 ,! coil z %[n is suitable = wave w9d+4 ,illu/ration3 ,,fig4 #che4--;,appe>ance ( /raight out coil aft] be+ op5$ out4 ,9 op5+ out ! coil1 ! ends ,c & ,f are put into a clamp & twi/$ at "r angles to ! plane ( ! coil4 ,! lett]s correspond to ! po9ts indicat$ 9 fig4 #chd4 ,ques4 ,h[ are /raight out coils plac$ on ! core8 ,ans4 ,9 ! same mann] z describ$ = evolute coils2 :5 9 position /raight out coils appe> z 9 fig4 #cgb4 ,ques4 ,:at is ! approv$ me?od ( putt+ tape on a coil8 ,ans4 ,consid]able "t is sav$ by ! use ( a ma*9e design$ = ! purpose1 su* z %[n 9 fig4 #chg4 ,illu/ration3 ,,fig4 #chf4 ,ano!r & simpl] me?od ( w9d+ a /raight out coil4 ,a bo>d ) only two p9s is employ$ z %[n2 ?is plan1 h[ev]1 gives m tr\ble 9 ! subsequ5t op5+ out ( ! coil4 ,! con/ruction ( ^! ma*9es is su* t a roll ( tape plac$ on a split metal r+ is revolv$ ar\nd ! coil to be tap$1 ! coil be+ gradually mov$ until x is entirely cov]$4 ,coil ,reta9+ ,devices4--,9 ! op]ation ( a dynamo !re are two =ces :i* t5d to ?r[ ! inductors out ( position3 #a4 ,armature drag2 #b4 ,c5trifugal =ce4 ,bo? ( ^! =ces are pres5t ) smoo? core armatures1 b only c5trifugal =ce ) slott$ armatures4 ,! devices us$ to hold ! inductors 9 position aga9/ ^! =ces are3 #a4 ,driv+ horns2 #b4 ,b9d+ ribbons2 #c4 ,reta9+ w$ges4 ,ques4 ,:at are driv+ horns8 ,ans4 ,!y are simply p9s or /rips project+ f ! surface ( a smoo? core z %[n 9 fig4 #bea4 ,illu/ration3 ,,fig4 #chg4--;,armature coil tap+ ma*9e4 ,num]\s ma*9es h be5 inv5t$ = tap+ armature coils4 ,!y consi/ ess5tially ( a device :i* revolves a roll ( tape ar\nd ! coil1 9 su* a direction t ! tape is unw\nd f ! roll & rew\nd on ! coil4 ,! spe$ at :i* ! coil is f$ ?r\gh ! ma*9e w det]m9e ! ov]lapp+ ( ! tape4 ,ques4 ,:at o!r k9ds ( reta9] are us$ on smoo? core armatures8 ,ans4 ,!y require sev]al b9d+ ribbons or brass b&s plac$ ar\nd ! w9d+ to prev5t ! inductors be+ ?r[n (f ! core by c5trifugal =ce4 ,ques4 ,) slott$ armatures :at provision mu/ be made = reta9+ ! inductors 9 position8 ,ans4 ,reta9+ w$ges mu/ be ins]t$ into ! not*es or betwe5 ! project+ tops ( ! tee?4 ,illu/ration3 ,,fig4 #chh4--;,front view ( l>ge armature = direct connect$ dynamo1 built by ! ,g5]al ,electric ,co4 ,ques4 ,h[ are ! w$ges made8 ,ans4 ,!y are usually made ( well bak$ h>d wood1 su* z hornbeam1 or h>d :ite vulcaniz$ fibre4 ,sometimes a spr+y /rip ( ,g]man silv] is us$4 ,,*apt] ,,xxiii ,,motors ,an electric motor is j ! rev]se ( a dynamo2 x is a ma*9e = conv]t+ electrical en]gy into me*anical en]gy4 ,! electrical en]gy deliv]$ by ! dynamo mu/ be obta9$ f a /eam eng9e1 gas eng9e1 or o!r p[]2 ! me*anical en]gy obta9$ f ! motor comes f ! en]gy ( ! curr5t fl[+ ?r\gh its armature4 ,ques4 ,:at is ! con/ruction ( a motor8 ,ans4 ,x is con/ruct$ 9 ! same mann] z a dynamo4 ,any ma*9e t c be us$ z a dynamo w1 :5 suppli$ ) electrical p[]1 run z a motor1 & conv]sely1 a motor :5 driv5 by me*anical p[]1 w supply electrical en]gy to ! circuit connect$ to x4 ,dynamos & motors1 !re=e1 are conv]tible ma*9es1 & ! diff]5ces t are f\nd 9 practice are l>gely me*anical2 !y arise *iefly f ! conditions "u :i* ! motor mu/ "w4 ,h5ce1 ! /udy ( ! motor beg9s ) a k ( ! dynamo1 & accord+ly ! /ud5t %\ld und]/& ?or\ghly all ! fundam5tal pr9ciples ( ! dynamo1 z already giv51 be=e proce$+ fur!r ) ! /udy ( ! motor4 ,pr9ciples ( ! ,motor4--,all ! e>ly attempts to introduce motors fail$1 *iefly because ! law ( ! cons]vation ( en]gy 0 n fully recogniz$4 ,?is law /ates t en]gy c nei!r be creat$ nor de/roy$4 ,e>ly exp]im5t]s discov]$1 by plac+ a galvanomet] 9 a circuit ) a motor & batt]y1 t1 :5 ! motor 0 runn+1 ! batt]y 0 unable to =ce ?r\gh ! wires s /rong a curr5t z t :i* fl[$ :5 ! motor 0 /&+ /ill4 ,moreov]1 ! fa/] ! motor ran1 ! weak] did ! curr5t become4 ,illu/ration3 ,,fig4 #chi4--;,conductor1 ly+ 9 a magnetic field & c>ry+ no curr5t2 ! field is n di/ort$ :e!r ! conductor be at re/ or 9 motion4 ,ques4 ,:y does less curr5t fl[ :5 ! motor is runn+ ?an :5 /&+ /ill8 ,ans4 ,because ! motor1 on acc\nt ( its rotation acts z a dynamo & ?us t5ds to set up 9 ! circuit a rev]se electromotive =ce1 t is1 an electromotive =ce 9 opposite direction to ! curr5t :i* is driv+ ! motor4 ,ques4 ,:at is ! real driv+ =ce :i* causes ! armature ( a motor to rotate8 ,ans4 ,! propell+ drag1 t is1 ! drag :i* ! magnetic field ex]ts ^u ! armature wires ?r\gh :i* ! curr5t is fl[+1 or 9 ! case ( deeply too!d cores1 ^u ! protrud+ tee?4 ,! ,propell+ ,drag4--,9 fig4 #chi is %[n ! condition :i* prevails :5 a conductor c>ry+ no curr5t is plac$ 9 a uni=m magnetic field4 ,! magnetic l9es pass /raight f "o pole to ! o!r4 ,! field is n di/ort$ :e!r ! conductor be at re/ or 9 motion1 s long z !re is no fl[ ( curr5t4 ,?is repres5ts ! condition 9 ! air gap ( a motor or dynamo1 :5 no curr5t is fl[+ 9 ! armature4 ,ques4 ,:at happ5s :5 a curr5t fl[s 9 ! conductor ( fig4 #chi4 ,ans4 ,x sets up a magnetic field ( its own z %[n 9 fig4 #cij4 ,ques4 ,:at is ! effect ( ?is magnetic field8 ,ans4 ,x di/orts ! orig9al field 7fig4 #chi7 9 :i* ! conductor lies1 mak+ ! magnetic l9es d5s] on "o side & less d5se on ! o!r z 9 fig4 #cij4 ,ques4 ,:at is ! nature ( ^! di/ort$ magnetic l9es8 ,ans4 ,!y t5d to %ort5 !mselves to _! orig9al =m ( /raight l9es4 ,ques4 ,:at effect has ?is on ! conductor8 ,ans4 ,x produces a =ce on ! conductor t5d+ to pu% x 9 ! direction indicat$ by ! arr[1 fig4 #cij4 ,illu/ration3 ,,fig4 #cij4--;,conductor c>ry+ a curr5t 9 a magnetic field4 ,! curr5t fl[+ 9 ! conductor sets up a magnetic field :i* di/orts ! orig9al field z %[n1 mak+ ! magnetic l9es d5s] on "o side & less d5se on ! o!r4 ,?is results 9 a =ce ^u ! wire1 :i*1 9 ! case ( a dynamo 7fig4 #cia7 opposes its movem5t1 & :i* =ms ! propell+ drag 9 ! case ( a motor 7fig4 #cib74 ,! di/ort$ magnetic l9es may be reg>d$ z s _m rubb] b&s t5d+ to /raight5 !mselves2 ,! result !n is cle>ly to =ce ! conductor 9 ! direction indicat$4 ,accord+ to ,l5z' law1 ! direction ( ! curr5t 9 ! armature ( a dynamo is su* z to oppose ! motion produc+ x4 ,:5 ! armature ( a dynamo is rotat$1 ! b5d+ ( ! l9es ( =ce ( ! ma9 magnetic field due to armature reaction acts z a drag aga9/ ! motion ( ! armature4 ,armature reaction increases ) ! increase ( ! armature curr5t4 ,!re=e1 ! effect ( ! drag increases ) ! increase ( load & requires an additional exp5diture ( p[] to drive ! armature4 ,9 a motor1 ! direction ( ! actuat+ curr5t is ! rev]se ( t ( ! armature curr5t ( a dynamo1 consequ5tly1 ! armature reaction :i* con/itutes a drag1 act+ aga9/ rotation ( ! armature ( a dynamo1 becomes a pull 9 ! direction ( rotation ( ! armature ( a motor & con/itutes its real turn+ effect or torque :i* is us$ at ! pulley to d me*anical "w4 ,! great] ! load appli$ to ! motor1 ! great] w be ! am\nt ( curr5t tak5 f ! supply ma9s1 & consequ5tly1 ! great] ! torque4 ,illu/ration3 ,,figs4 #cia & #cib4--;,action ( ! magnetic =ce 9 a dynamo & motor4 ,9 ! fir/ in/ance1 accord+ to ,l5z' law1 ! direction ( ! curr5t induc$ 9 ! wire is su* z to oppose ! motion produc+ x4 ,9 ! op]ation ( a motor1 ! curr5t suppli$ 9 fl[+ ?r\gh ! armature w9d+ di/orts ! field & ?us produces rotation4 ,9 ! figures1 ! direction ( ! =ce is cle>ly indicat$ by rememb]+ t ! di/ort$ l9es ( =ce act l rubb] b&s t5d+ to /raight5 & %ort5 !mselves4 ,ques4 ,:at are ! ess5tial requirem5ts ( con/ruction 9 a motor8 ,ans4 ,!y are3 #a1 a magnetic field1 #b1 conductors plac$ p]p5dicul> to ! field1 & #c1 provision = motion1 ( ! conductors across ! field 9 a direction p]p5dicul> to bo? !mselves & ! field4 ,! ,rev]se ,electromotive ,=ce4--,:5 an electric curr5t fl[s ?r\gh "s portion ( a circuit 9 :i* !re is an electromotive =ce1 ! curr5t w !re ei!r receive or give up en]gy1 accord+ to :e!r ! electromotive =ce acts ) or aga9/ ! curr5t4 ,illu/ration3 ,,fig4 #cic4--;,=ce ex]t$ on a curr5t c>ry+ conductor plac$ across a magnetic field4 ,let ,n1 ,s1 be ! pole pieces ( an ord9>y electromagnet1 hav+ _! faces flat & ) only a n>r[ air gap betwe54 ,9 ?is gap is /ret*$ ! v]tical copp] wire ,a ,b1 kept taut by a /rong spr+ at ,a2 curr5t c be pass$ into ! wire f ! leads ,c & ,d4 ,atta*$ to ! wire 9 ! middle ( ! gap is a horizontal cord pass+ ov] a pulley ,p & kept taut by a weight ,w2 ! pulley c>ries a po9t] ,f :i* moves 9 front ( a scale s s4 ,if ! electromagnet be n[ excit$ & h ! pol>ity indicat$1 x w be f\nd t on pass+ a /rong curr5t d[n ! wire1 ! index ,f moves t[>d ! "r1 %[+ a simil> movem5t 9 ! wire4 ,! index returns to z]o :5 ! curr5t 9 ! wire ceases1 & moves 9 ! opposite direction if ! curr5t 9 ! wire be rev]s$ & s5t up in/ead ( d[n4 ,! exp]im5t c be fur!r v>i$ by rev]s+ ! magnetiz+ curr5t ( ! electromagnet4 ,?is is illu/rat$ 9 fig4 #cie1 :i* repres5ts a circuit 9 :i* !re is a dynamo & a motor4 ,ea* is rotat+ clockwise1 & accord+ly1 ea* g5]ates an electromotive =ce t5d+ upw>d f ! l[] to ! upp] bru%4 ,9 bo? cases ! upp] bru% is positive4 ,9 ! dynamo1 h[ev]1 :]e en]gy is be+ suppli$ to ! circuit1 ! electromotive =ce is 9 ! same direction z ! curr5t1 & 9 ! motor1 :]e "w is be+ done1 ! electromotive =ce is 9 ! rev]se direction to t ( ! dynamo4 ,illu/ration3 ,,fig4 #cid4--,%[+ relative directions ( armature curr5t & rev]se electromotive =ce ( a motor4 ,:5 a motor is 9 op]ation1 ! wires ar\nd ! p]iph]y ( its armature cut ! magnetic l9es ( =ce produc$ by ! field magnet exactly z 9 ! case ( ! dynamo4 ,consequ5tly1 an electromotive =ce is induc$ 9 ea* wire1 z 9 ! dynamo armature4 ,?is induc$ electromotive =ce is 9 opposition to ! fl[ ( curr5t due to ! electromotive =ce ( ! supply circuit1 & t5ds1 !re=e1 to keep d[n ! fl[ ( curr5t4 ,! figure %[s a s+le loop ( wire1 on ! armature core connect$ directly to ! s\rce ( electricity4 ,) curr5t fl[+ 9 ! loop 9 ! direction indicat$ by ! arr[s m>k$ c1 a magnetic field is set up 9 ! direction indicat$ by ! l>ge arr[ m>k$ direction ( armature flux4 ,) ! field magnet en]giz$ s z to produce a field 9 ! direction indicat$ by ! l>ge arr[ ,f1 ! reaction betwe5 ! two fields w turn ! armature core 9 ! direction indicat$ by ! arr[ ,r4 ,z ! core turns1 ! upp] wire ( ! loop w cut ! flux "u ! s\? pole ( ! field magnet1 & ! o!r side ( ! loop w cut ! flux "u ! nor? pole4 ,! result w be ! induction ( a rev]se electromotive =ce 9 ! loop1 ! direction be+ indicat$ by ! small arr[s m>k$ e4 ,! actual fl[ ( curr5t 9 ! armature is t due to ! diff]5ce betwe5 ! impress$ & rev]se voltage2 ! latt] is proportional to ! spe$ ( ! armature1 ! numb] ( armature wires & ! /r5g? ( ! magnetic field 9 ! air gaps betwe5 ! armature & ! pole faces4 ,! spe$ ( a motor suppli$ ) curr5t at con/ant voltage v>ies directly ) ! rev]se electromotive =ce1 also ) o!r conditions fix$1 ! /rong] ! field1 ! sl[] ! spe$4 ,weak5+ ! field w increase ! spe$ up to ! po9t :]e ! increase 9 rev]se electromotive =ce due to ! increas$ spe$ cuts d[n ! armature curr5t bel[ ! value necess>y to give ! requisite pull at ! armature p]iph]y4 ,:5 ?is po9t is rea*$1 any weak5+ ( ! field w r$uce ! spe$ ( ! armature4 ,! pull or torque ( a motor armature is directly proportional to ! /r5g? ( ! magnetic field1 & to ! /r5g? ( ! armature curr5t1 ! numb] ( armature inductors be+ fix$4 ,9 a field ( con/ant /r5g?1 !re=e1 ! pull ( ! armature dep5ds on ! am\nt ( curr5t pass+ ?r\gh ! w9d+4 ,! torque mu/ be j suffici5t to ov]come ! load2 if 9 excess1 ! spe$ w increase until ! increase ( ! rev]se electromotive =ce r$uces ! curr5t & ! increase ( spe$ increases ! load to ! po9t ( equilibrium betwe5 load & torque4 ,if ! torque be insuffici5t = ! load1 ! spe$ w dim9i% until equilibrium is e/abli%$1 assum+ ! motor is runn+ on con/ant voltage circuit4 ,ques4 ,describe simil> conditions :i* prevail 9 ! op]ation ( a dynamo4 ,ans4 ,:5 no curr5t is be+ g5]at$ by ! dynamo1 little p[] is requir$ to drive x1 b :5 ! ext]nal circuit is clos$ & curr5t is =c$ ?r\gh x aga9/ m or less resi/ance1 "w is be+ done1 h5ce m p[] is requir$4 ,9 o!r words1 !re is an opposition to ! me*anical =ce appli$ at ! pulley :i* is proportional to ! electric p[] deliv]$ by ! dynamo4 ,an oppos+ reaction or rev]se =ce !n is set up 9 a dynamo :5 x does "w4 ,illu/ration3 ,,fig4 #cie4--;,circuit ) g5]ator & motor4 ,:5ev] curr5t fl[s ?r\gh "s portion ( a circuit 9 :i* !re is an electromotive =ce1 ! curr5t w !re ei!r receive or give up en]gy accord+ to :e!r ! electromotive =ce acts ) ! curr5t or aga9/ x4 ,9 ! figure1 ! g5]ator & motor are rotat+ clockwise1 & h5ce ea* g5]ates an electromotive =ce t5d+ upw>ds f ! l[] bru% to ! high]4 ,9 ea* case ! upp] bru% is ! positive "o4 ,9 ! dynamo1 :]e en]gy is be+ suppli$ to ! circuit1 ! electromotive =ce is 9 ! same direction z ! curr5t1 :ile 9 ! motor :]e "w is be+ done & en]gy is leav+ ! circuit1 ! electromotive =ce is 9 a direction :i* opposes ! curr5t4 ,ques4 ,9 ! op]ation ( a motor :at is ! nature ( ! rev]se electromotive =ce8 ,ans4 ,x is proportional to ! velocity ( rotation1 ! /r5g? ( ! magnets1 & to ! numb] & arrangem5t ( ! wires on ! armature1 t is1 ! rev]se voltage dep5ds on ! rate at :i* ! l9es ( =ce are cut4 ,illu/ration3 ,,figs4 #cif & #cig4--,wat] & electric circuits4 ,diagrams %[+ comp>ison betwe5 wat] motor & electric motor4 ,9 ! diagrams3 ,! pump corresponds to ! dynamo4 ,! high level pipe positive conductor4 ,! l[ level pipe negative conductor4 ,! valve swit*4 ,! wat] motor electric motor4 ,! wat] pressure 7call$ head7 electric pressure 7call$ voltage74 ,! fl[ 9 gallons p] m9ute amp]es4 ,! size ( pipe size ( conductor4 ,! foot p\nds watts4 ,! great] ! diff]5ce betwe5 ! height ( ! two pipes ! high] ! pressure1 & ! great] ! diff]5ce betwe5 ! pressures ( ! two conductors ! high] ! voltage4 ,! l>g] ! diamet] ( ! pipes ! less resi/ance is (f]$ to ! fl[ ( wat]1 & ! l>g] ! diamet] ( ! conductors ! less resi/ance is (f]$ to ! fl[ ( electricity4 ,! m wat] requir$ by ! wat] :eel1 ! m p[] is requir$ to drive ! pump4 ,! m electricity requir$ by ! motor ! m p[] is requir$ to drive ! g5]ator4 ,illu/ration3 ,,fig4 #cih4--;,fairbanks-,morse /&>d ,,tr type motor4 ,?is type is built 9 ! small] sizes & ! design is su* t ! motor c be in/all$ ^u ! floor1 wall or ceil+1 ! be>+ yokes be+ atta*$ to ! frame by f\r equally spac$ bolts s t !y c be turn$ to provide = prop] op]ation ( ! oil+ devices 9 ei!r position4 ,a sub/antial base is provid$ ) a ?ru/ screw = adju/+ ! belt t5sion4 ,?is base has clamp+ bolts :i* p]mit adju/+ ! position ( ! motor :ile susp5d$4 ,!re is a ca/ r+ type frame hav+ /eel side pieces :i* press firmly toge!r1 ! /eel lam9ations mak+ up ! pole pieces4 ,! field coils armature1 & armature coils are illu/rat$ 9 detail 9 figs4 #cii to #dja4 ,! commutator b>s are ( drawn copp]1 insulat$ ) mica4 ,! lugs :i* ext5d outw>d f ! b>s to receive ! lead wires f ! armature w9d+s are =m$ 9 "o piece ) ! b>s1 & are ( ! full wid? ( ! b>s ) ! insulator ext5d+ outw>d betwe5 !m1 s t :5 assembl$ a solid flange is =m$ to receive ! armature connections4 ,self-oil+ be>+s are provid$ & ! location ( ! be>+ sleeves 9 ! h\s+ is adju/able s t ! armature may be c5t]$ 9 ! magnetic field4 ,! bru% rigg+ is c>ri$ on a skeleton rock] support$ 9 a groove1 turn$ 9 ! edge ( ! frame4 ,! bru% hold]s are ( ! box type ) indep5d5tly adju/able t5sion spr+ = ea*4 ,/&>d %unt w9d+s are = #aae1 #bcj & #eej volts4 ,! comp\nd w\nd motors op]ate at approximately ! same full load spe$s z ! %unt w\nd1 b ! no load spe$s w be ab\t #bj p] c5t4 high] ?an ! full load spe$s4 ,!y h1 h[ev]1 ! ability to ex]t a m p[]ful />t+ ef=t ?an %unt motors )\t draw+ su* a heavy curr5t f ! l9e1 & are1 !re=e1 especially adapt$ = driv+ app>atus t has to be frequ5tly />t$ & /opp$ "u load & :]e close spe$ regulation is n requir$4 ,ques4 ,describe an exp]im5t :i* %[s ! exi/5ce ( a rev]se electromotive =ce 9 a motor4 ,ans4 ,! app>atus requir$ consi/s ( a small motor1 batt]y1 & ammet]4 ,!y %\ld be connect$ 9 "o circuit & ! deflection ( ! ammet] obs]v$ :5 ! armature is held /ation>y1 & :5 x rotates ) v>i\s loads4 ,9 an exp]im5t ( ?is k9d made on a motor ) sep>ately excit$ magnets1 ! foll[+ figures 7 obta9$3 ,revolutions p] m9ute #j #ej #ajj #afj #ahj #aie ,amp]es #bj #af4b #ab4b #g4h #f4a #e4a ,app>5tly1 if ! motor _h be5 help$ on to run at #bfa revolutions p] m9ute1 ! curr5t w\ld h be5 r$uc$ to z]o4 ,9 ! la/ result obta9$1 ! curr5t ( #e4a amp]es 0 absorb$ 9 driv+ ! armature aga9/ its own friction at ! spe$ ( #aie revolutions p] m9ute4 ,illu/ration3 ,,fig4 #cii4--;,fairbanks-,morse field coil & pole piece4 ,! field coils are w\nd ^u iron =ms1 ea* lay] treat$ ) insulat+ comp\nd4 ,aft]w>d !y are remov$ f ! =ms & bak$ h>d & dry & f9ally wrapp$ ) insulat+ mat]ials2 all b ! ?ree small] sizes are wrapp$ ) a protect+ cord4 ,! s]ies & %unt coils ( ! comp\nd w9d+ "h %[n are w\nd sep>ately1 ! small] "o be+ ! s]ies coil & ! l>g] ! %unt coil4 ,ques4 ,expla9 ! action ( ! curr5t suppli$ to a motor = its op]ation4 ,ans4 ,! motor curr5t pass+ ?r\gh ! field magnets pol>izes !m & e/abli%es a magnetic field1 & ent]+ ! armature1 pol>izes its core 9 su* a way t ! positive pole ( ! core is away f ! negative pole ( ! magnetic field1 & ! negative pole is away f ! positive pole ( ! magnetic field4 ,! magnetic repulsions & attractions ?us creat$ cause ! armature to rotate 9 a position ( magnetic equilibrium or s z to br+ its positive & negative poles opposite ! negative & positive poles respectively ( ! magnetic field4 ,x is evid5t t unless suitable means 7 provid$ to rev]se ! pol>ity ( ! armature core at ! in/ant x rea*$ ! position ( ! magnetic equilibrium1 ! armature w\ld n rotate any fur!r4 ,! con/ruction is su* t ! pol>ity ( ! armature core1 or ! direction ( ! curr5t 9 ! armature coils is rev]s$ at ! prop] in/ant automatically by ! commutator1 ?us giv+ cont9u\s rotation4 ,illu/ration3 ,,fig4 #djj4--;,fairbanks-,morse armature = #g ,h4,p41 #acjj ,r4,p4,m41 ,,tr type motor4 ,! armature core is built up ( ?9 %eet /eel lam9ations ) not*es 9 ! circumf]5ce1 :i*1 :5 ! discs are plac$ toge!r1 =m grooves or slots to receive ! armature coils4 ,! armature cores = ! l>g] ma*9es are m\nt$ on a ca/ iron spid]1 :i* also c>ries ! commutator1 mak+ ! two p>ts entirely self-conta9$1 & ) ?is con/ruction1 x is possible to remove ! armature %aft1 )\t di/urb+ ! core1 commutator or w9d+s4 ,cores ( all sizes are provid$ ) v5tilat+ spaces1 runn+ f ! surface to ! c5tral op5+ ( ! core1 s t air is drawn ?r\gh ! core & bl[n out ov] ! w9d+s by ! revolution ( ! armature4 ,direction ( ,rotation ( ,motors4--,9 ! case ( ei!r a motor1 or a dynamo us$ z a motor1 ! direction 9 :i* ! armature w rotate is easily f\nd by ! left h& rule1 z illu/rat$ 9 fig4 #daa1 :5 ! pol>ity ( ! field magnets & ! direction ( curr5ts ?r\gh ! armature are kn[n4 ,ques4 ,h[ may ! rotation ( a motor be rev]s$8 ,ans4 ,by rev]s+ ei!r ! curr5t ?r\gh ! fields1 or ! curr5t ?r\gh ! armature4 ,ques4 ,:at w happ5 if bo? curr5ts be rev]s$8 ,ans4 ,! motor w run 9 ! same direction z be=e4 ,illu/ration3 ,,fig4 #dja4--;,fairbanks-,morse wire w\nd armature coils4 ,^! coils are =m w\nd & are ?or\ghly insulat$ & bak$ be=e assembl+ 9 ! slots4 ,mat]ial ( great me*anical /r5g? z well z high insulat+ value is us$1 & ! coils are subject$ to dipp+s 9 insulat+ comp\nd & to bak+s1 ?us driv+ out all moi/ure & mak+ a coil :i* is practically wat]pro( & :i* w )/& r\gh h&l+4 ,^! coils1 :5 complet$1 are plac$ 9 ! slots1 :]e !y are reta9$ by b&s on ! ?ree small] sizes & by h>dwood w$ges on ! l>g] sizes4 ,ques4 ,:at is ! effect ( supply+ curr5t to a s]ies dynamo8 ,ans4 ,x w run 9 a direction opposite to its motion z a dynamo4 ,ques4 ,:at is ! result ( rev]s+ ! direction ( curr5t at ! t]m9als ( a s]ies motor8 ,ans4 ,x w n *ange its direction ( rotation1 s9ce ! curr5t /ill fl[s ?r\gh ! armature 9 ! same direction z ?r\gh ! field4 ,illu/ration3 ,,figs4 #djb to #daj4--;,diagrams %[+ relative direction ( rotation ( motors & dynamos4 ,f figs4 #cia & #cib1 x is se5 t ! direction ( ! curr5t 9 a motor armature mu/ be su* z w increase1 by ! flux x produces1 ! int5sity at ! lead+ pol> edge & decrease ! int5sity at ! trail+ pol> edge4 ,9 a dynamo1 ! armature has to be mov$ by me*anical =ce1 aga9/ a magnetic =ce1 h5ce ! lead+ pol> edge is weak5$1 :ile ! trail+ edge is /r5g!n$4 ,! magnetomotive =ce 9 a motor armature is1 !re=e1 oppos$ to ! direction ( t 9 a g5]ator armature1 :5 ! direction ( rotation & ! direction ( ! field magnetomotive =ce are ! same4 ,^u ?is dep5ds all ! relations exi/+ betwe5 ! direction ( rotation ( a ma*9e :5 act+ z a motor or z a dynamo4 ,ques4 ,:at is ! behavior ( a %unt dynamo :5 us$ z a motor8 ,ans4 ,its direction ( rotation rema9s un*ang$4 ,ques4 ,:y is ?is8 ,ans4 ,because if ! connections be su* t ! curr5t suppli$ w fl[ ?r\gh ! armature 9 ! same direction z :5 ! ma*9e is us$ z a dynamo1 ! curr5t ?r\gh ! field w be rev]s$1 s9ce ! field w9d+s are 9 p>allel ) ! bru%es4 ,illu/ration3 ,,fig4 #daa4--,! left h& rule = direction ( motion 9 motors4 ,place ! left h&1 z %[n1 s t ! ?umb po9ts 9 ! direction ( ! curr5t1 ! #crd1 #d? & #e? f+]s 9 ! direction ( ! l9es ( =ce1 !n w ! #bnd or =ef+]1 at "r angles to ! o!rs1 po9t 9 ! direction 9 :i* ! conductor is urg$4 ,armature ,reaction 9 ,motors4--,9 ! op]ation ( a motor ! reaction betwe5 ! armature & field magnets di/orts ! field 9 a simil> mann] z 9 ! op]ation ( a dynamo4 ,a curr5t suppli$ f an outside s\rce magnetizes ! armature ( a motor & trans=ms x into an electromagnet1 ^: poles w\ld lie ne>ly at "r angles to ! l9e jo9+ ! pole pieces1 7 x n = ! fact t negative lead mu/ be giv5 to ! bru%es4 ,illu/ration3 ,,fig4 #dab4--,pr9ciple ( ! electric motor z illu/rat$ by exp]im5t %[+ effect ( a magnetic field on a wire c>ry+ an electric curr5t4 ,let a v]tical wire ab be rigidly atta*$ to a horizontal wire gh1 & let ! latt] be support$ by a r+ or o!r metallic support z %[n1 s t ab is free to oscillate ab\t gh z an axis4 ,let ! l[] end ( ab dip into a tr\gh ( m]cury4 ,:5 a magnet is held 9 ! position %[n & a curr5t f a cell is s5t ?r\gh ! wire z indicat$1 ! wire w move 9 ! direction %[n by ! arr[ f1 t is1 at "r angles to ! direction ( ! l9es ( magnetic =ce4 ,let ! direction ( ! curr5t 9 ! wire be rev]s$1 !n ! direction ( ! =ce act+ on ! wire w be f\nd to be rev]s$ also4 ,! conclusion is t a wire c>ry+ a curr5t 9 a magnetic field t5ds to move 9 a direction at "r angles bo? to ! direction ( ! field & to ! direction ( ! curr5t4 ,! relation betwe5 ! direction ( ! magnetic l9es1 ! direction ( ! curr5t1 & ! direction ( ! =ce1 is (t5 rememb]$ by means ( ! foll[+ rule1 kn[n z ! motor rule1 & :i* diff]s f ! dynamo rule only 9 t x is appli$ to ! f+]s ( ! left h& in/ead ( to ^? ( ! "r4 ,let ! =ef+] ( ! left h& po9t 9 ! direction ( ! magnetic l9es ( =ce & ! middle f+] 9 ! direction ( ! curr5t s5t ?r\gh ! wire1 !n w ! ?umb1 at "r angles to ! o!r two f+]s1 po9t 9 ! direction 9 :i* ! wire is urg$4 ,negative lead is ! am\nt ( backw>d advance ( ! bru%es aga9/ ! direction ( ! rotation ( ! armature1 measur$ 9 degrees f ! neutral plane4 ,if ! bru%es be giv5 positive lead1 t is1 plac$ 9 advance ( ! neutral plane 9 ! direction ( rotation1 ! cross magnetiz+ =ce is conv]t$ into "o t t5ds to increase t ( ! field magnet1 :ile if !y be giv5 negative lead1 x t5ds to demagnetize ! field magnet4 ,s9ce ) positive lead ! armature pol>ity /r5g!ns t ( ! field magnet1 x is possible1 disreg>d+ sp>k+1 to op]ate a motor )\t any o!r means be+ tak5 to magnetize ! field magnets1 because ! armature w induce a pole 9 ! field magnet & !n attract itself t[>ds ?is induc$ pole4 ,ques4 ,:at effect has ! cross magnetiz+ =ce on ! field8 ,ans4 ,x t5ds to %ift ! field ar\nd 9 a direction opposite to t ( ! rotation4 ,illu/ration3 ,,fig4 #dac4--;,curr5t commutation 9 a motor4 ,consid]+ ! coil ,w :i* is asc5d+1 curr5t is fl[+ ?r\gh x f ! top bru%1 :ile x is itself ! seat ( an electromotive =ce t t5ds to /op or rev]se its curr5t4 ,! condition = sp>kless commutation requires t dur+ ! int]val ! coil is %ort circuit$ by ! bru%1 ! coil %\ld be pass+ ?r\gh a field t is n only suffici5tly /rong b "o t t5ds to rev]se ! direction ( its curr5t4 ,! coil is already 9 su* a field1 h5ce1 commutation mu/ take place be=e x passes put ( ?is field4 ,to accompli% ?is ! bru%es mu/ be %ift$ backw>d1 t is1 giv5 negative lead1 to ov]come sp>k+4 ,9 o!r words1 ! commutat+ plane mu/ be %ift$ back ( ! neutral plane 9 a motor in/ead ( be+ plac$ 9 advance z 9 a dynamo4 ,ques4 ,:at are ! conditions ( m9imum sp>k+8 ,ans4 ,! same conditions mu/ obta9 z 9 a dynamo1 t is1 ! curr5t 9 ! coil und]go+ commutation mu/ be br\ght to re/ & />t$ aga9 9 ! opposite direction4 ,?is involves t :ile ! coil is %ort circuit$ by ! bru%1 x %\ld be pass+ ?r\gh a field t t5ds to rev]se ! direction ( ! curr5t4 ,s9ce ! coil is already 9 su* a field1 ! act ( commutation mu/ take place be=e x passes out ( ?is field4 ,accord+ly1 a negative lead mu/ be giv5 ! bru%es4 ,illu/ration3 ,,fig4 #dad4--,railway motor4 ,?is type ( motor1 s9ce x mu/ op]ate "u c>s1 has tak5 on ! peculi> =m "u :i* x is mo/ famili>4 ,z illu/rat$1 ! case is ( su* %ape t compactness & wat] pro(+ are secur$1 & ! means ( atta*m5t to ! c> axle & support f ! axle & truck frame are provid$4 ,me?od ( ,/>t+ a ,motor4--,al?\gh motors & dynamos are practically simil> 9 g5]al con/ruction & ei!r "o ( !m w act z ! o!r :5 suitably trav]s$ by an electric curr5t1 !re are c]ta9 diff]5ces betwe5 ! connections & accessories ( a ma*9e op]at$ z g5]ator & "o employ$ z a motor4 ,= in/ance1 :5 a ma*9e is op]at$ z a dynamo1 x is fir/ driv5 up to spe$ until x has excit$ itself to ! "r pressure1 & !n x is connect$ to ! circuit2 b :5 a ma*9e is us$ z a motor x w n />t until x has be5 connect$ to ! circuit1 & ?is mu/ n be done until ! prop] precautions h be5 tak5 to ensure t ! curr5t1 :i* w pass ?r\gh x :5 s connect$1 w n be excessive & !reby result 9 s]i\s injury to ! motor4 ,= ?is reason a rheo/at or v>iable resi/ance1 commonly call$ a />t+ box is usually ins]t$ 9 ! armature circuit ( a motor to prev5t an undue ru% ( curr5t be=e ! motor atta9s its spe$1 & subsequ5tly ! spe$ is regulat$ by ! cutt+ 9 or out ( ! circuit ( c]ta9 extra resi/ances :i* con/itute ! controll] us$ on a s]ies motor requir+ v>iable torque at v>iable spe$1 z 9 ! case ( elevator or electric traction s]vice4 ,illu/ration3 ,,fig4 #dae4--,view ( railway motor1 op54 ,! frame is ( ca/ /eel = lightness1 & :i* s]ves z magnetic circuit & protect+ case4 ,x is circul> or octagonal 9 =m except 9 v l>ge motors4 ,f\r %ort magnets project f ! case4 ,! armature is l>ge 9 ord] to secure ! requir$ torque4 ,x is always s]ies w\nd1 requir+ two bru%es4 ,! bru% hold]s are m\nt$ ^u a frame ( insulat+ mat]ial :i* is atta*$ to ! upp] half ( ! case4 ,! bru%es are adju/able radially1 b usually x is n necess>y to provide = %ift+ z !y rema9 9 ! neutral plane4 ,9 motors :i* receive s little att5tion z ^!1 special att5tion mu/ be giv5 to ! design ( devices = keep+ oil & grease out ( ! case4 ,^! w\ld injure ! insulation ( ! coils & produce sp>k+ at ! commutator4 ,oil r+s are1 !re=e1 plac$ on ! %aft1 & ^! dis*>ge into *amb]s connect$ to ! oil wells or all[ ! oil to ov]fl[ on ! track4 ,! be>+s are made self-oil+ or self-greas+ by means ( r+s or wicks & w run = weeks )\t att5tion4 ,classes ( ,motor4--,motors are classifi$ 9 ! same mann] z dynamos4 ,! fields may be ei!r bipol> or multi-pol>1 & ) respect to ! type ( armature w9d+ employ$1 motors are class$ z3 #a4 ,s]ies w\nd2 #b4 ,%unt w\nd2 #c4 ,comp\nd w\nd4 ,illu/ration3 ,,fig4 #daf4--,s]ies motor connections4 ,a s]ies motor on a con/ant voltage circuit does n h a con/ant field /r5g?1 & does n run at uni=m spe$4 ,if ! load be tak5 (f x w run at excessive spe$4 ,to />t ! motor1 ! circuit is complet$ ?r\gh a v>iable resi/ance or rheo/at by mov+ ! swit* ,s s t ! resi/ances ,r1 ,r#a1 ,r#b1 ,r#c1 are gradually cut out ( ! circuit4 ,to /op1 ! swit* ,s is mov$ back to its (f position4 ,s]ies ,motors4--,a s]ies motor is "o 9 :i* ! field magnet coils1 consi/+ ( a few turns ( ?ick wire1 are connect$ 9 s]ies ) ! armature s t ! :ole curr5t suppli$ to ! motor passes ?r\gh ! field coils z well z ! armature4 ,fig4 #daf is a diagram ( a s]ies motor %[+ ! connections & rheo/at4 ,ques4 ,:at are ! *>act]i/ics ( a s]ies motor8 ,ans4 ,! field /r5g? increases ) ! curr5t1 s9ce ! latt] fl[s ?r\gh ! magnet coils4 ,if ! motor be run on a con/ant voltage circuit1 ) light load1 x w run at a v high spe$2 aga91 if ! motor be load$ heavily1 ! spe$ w be mu* less ?an be=e4 ,illu/ration3 ,,fig4 #dag4--;,g5]al ,electric type ,,cl-,b motor = sl[ & mod]ate spe$s4 ,x is ( multipol> con/ruction1 hav+ six pole pieces4 ,! advantages ( sl[ spe$ ma*9]y are g5]ally und]/ood1 & 9 motors ! additional outlay to secure sl[ spe$s is w>rant$1 inasmu* z x results 9 dim9i%$ we> & friction losses 9 ge>+1 belt+1 be>+s1 & commutators1 & decreas$ bru% r5ewals4 ,! comp>atively sl[ spe$s ( ^! motors are ( importance 9 t !y p]mit belt+ or ge>+ ! motors directly to ord9>y sl[ spe$ l9e %aft+ )\t employ+ int]m$iate c\nt] %aft+4 ,:5 motors are ge>$ to heavy duty ma*9es1 x is consid]$ bett] practice to supply an outbo>d be>+ to take up ! additional /ra9 t w\ld o!rwise be put on ! ge>+ & be>+4 ,ques4 ,= :at k9ds ( s]vice are s]ies motors unsuit$8 ,ans4 ,s]ies motors %\ld n be employ$ :]e ! load may be entirely remov$ because !y w\ld atta9 a dang]\s spe$4 ,!y %\ld n be us$ = driv+ by means ( belts1 because a sudd5 release ( ! load due to a mi%ap to ! belt w\ld cause ! motor to run away4 ,v small s]ies motors may be us$ ) belts s9ce _! comp>atively l>ge frictional resi/ance repres5ts an appreciable load1 re/ra9+ ! motor f rea*+ a dang]\s spe$4 ,ques4 ,= :at s]vice are s]ies motors adapt$8 ,ans4 ,= ge> drive4 ,9 ! case ( a sudd5 release ( ! load ! ge>s provide "s load on acc\nt ( ! frictional resi/ance ( ! ge> tee?4 ,illu/ration3 ,,fig4 #dah4--,%unt motor connections4 ,a %unt motor runs at con/ant spe$ on a con/ant voltage circuit4 ,9 connect+ ! motor 9 circuit1 ! field coils mu/ be plac$ 9 circuit fir/1 s t !re is a c]ta9 am\nt ( field /r5g? to produce rotation ( ! armature & ?us prev5t excessive curr5t ?r\gh ! armature4 ,if ! field magnets 7 n put 9 ! circuit fir/1 ! armature1 at re/ on receiv+ curr5t1 w\ld probably burn out1 because x is ( l[ resi/ance1 & w\ld take practically all ! curr5t suppli$1 especially s9ce no rev]se voltage is g5]at$ 9 ! armature at re/4 ,! me?od ( />t+ is %[n 9 ! illu/ration4 ,to />t1 ! swit* is clos$1 & ! rheo/at lev] pu%$ ov] s z to make contact ) ,a & ,b1 ?us fir/ excit+ ! magnets4 ,on fur!r movem5t ( ! lev]1 ! rheo/at resi/ances ,r1 ,r#a1 ,r#b1 ,r#c1 etc41 are gradually cut out z ! spe$ increases1 until f9ally all ! resi/ance coils are cut out4 ,to /op1 ! lev] is br\ght back to its orig9al position4 ,ques4 ,:at advantage is obta9$ ) s]ies motors ) respect to ! connections8 ,ans4 ,a s+le wire only proce$s f ! rheo/at to ! motor1 s t1 ) ! return wire1 only two wires are requir$4 ,ques4 ,= :at s]vice are s]ies motors specially adapt$8 ,ans4 ,s]ies motors are us$ pr9cipally = electric railways1 trolleys1 & electric vehicles1 & simil> purposes :]e an att5dant is always at h& to regulate or control ! spe$4 ,!y are also us$ on s]ies arc light circuits 9 :i* ! curr5t is ( con/ant /r5g?4 ,v small motors are g5]ally provid$ ) s]ies w9d+s4 ,illu/ration3 ,,fig4 #dai4--,spe$ regulation ( a %unt motor4 ,! spe$ ( a motor dep5ds on ! voltage ( ! curr5t suppli$ & ! field /r5g?4 ,! motor t5ds to rotate s fa/ z to produce a rev]se voltage ne>ly equal to t suppli$ to ! bru%es2 h5ce1 ! spe$ v>ies ) ! voltage suppli$4 ,by decreas+ ?is voltage !n1 ! spe$ is decreas$4 ,accord+ly1 ! spe$ may be r$uc$ by ins]t+1 by means ( a rheo/at1 a resi/ance 9 s]ies ) ! motor4 ,by ins]t+ ?is resi/ance 9 ! field circuit1 ! voltage at ! t]m9als ( ! motor is l[]$1 ?us giv+ ! condition necess>y to r$uce ! spe$4 ,! arrangem5t = spe$ regulation %[n 9 ! figure includes a />t+ regulator & a %unt regulator4 ,%unt ,motors4--,a %unt motor may be def9$ z "o 9 :i* ! field coils are w\nd ) _m turns ( comp>atively f9e wire1 connect$ 9 p>allel ) ! bru%es4 ,! curr5t !n is (f]$ two pa?s3 "o ?r\gh ! armature1 & "o ?r\gh ! field coils4 ,illu/ration3 ,,figs4 #dbj to #dbb4--,rev]s+ ! direction ( rotation ( a s]ies motor4 ,fig4 #dbj %[s ! connections = c\nt] clockwise rotation4 ,! motor may be rev]s$3 #a1 by all[+ ! curr5t to fl[ 9 its orig9al direction 7f ,d to ,c7 9 ! field magnet coils1 & alt]+ ! direction ( ! armature curr5t by *ang+ ! two connections on ! bru%es ,a & ,b1 ?us connect+ ,c to ,a & ,b to ! return wire z 9 fig4 #dba1 or #b1 by leav+ ! direction ( ! curr5t 9 ! armature 9 its orig9al direction1 & rev]s+ t ( ! field curr5t1 z 9 fig4 #dbb4 ,if ! wires lead+ to ! rheo/at & motor directly1 7 rev]s$ !re w\ld be no rev]sal ( ! motor1 because by s do+1 bo? ! armature & field magnet curr5ts w\ld be rev]s$4 ,illu/ration3 ,,figs4 #dbc to #dbe4--,rev]s+ ! direction ( rotation ( a %unt motor4 ,fig4 #dbc %[s ! connections = c\nt] clockwise rotation4 ,! motor may be rev]s$3 #a1 by all[+ ! curr5t to fl[ 9 its orig9al direction ?r\gh ! field magnet coils 7f ,d to ,c71 & rev]s+ its direction ?r\gh ! armature 7f ,a to ,b7 z 9 fig4 #dbd1 or #b1 by all[+ ! armature curr5t to fl[ 9 its orig9al direction 7f ,b to ,a7 & rev]s+ ! curr5t ?r\gh ! field coils 7f ,c to ,d7 z 9 fig4 #dbe4 ,ques4 ,:at may be said ) respect to ! spe$ ( a %unt motor8 ,ans4 ,x is practically con/ant ) v>y+ loads4 ,! v>iation ( spe$ ranges f #a_/aj to #e p] c5t41 except 9 ! case ( small motors1 9 :i* ! v>iation may be mu* great]4 ,ques4 ,h[ %\ld a %unt motor be />t$8 ,ans4 ,to prop]ly />t ! ma*9e1 ! field coils mu/ be fully excit$4 ,x is1 !re=e1 necess>y to swit* ! magnet coils imm$iately on to ! voltage ( supply1 :ile a v>iable resi/ance mu/ be provid$ = ! armature circuit4 ,to get bo? connections at ! same "t1 rheo/ats = %unt motors are arrang$ z %[n 9 fig4 #dah4 ,influ5ce ( ,bru% ,position on ,spe$4--,9 ! case ( a %unt motor suppli$ ) curr5t at con/ant pressure1 ! spe$ is a m9imum :5 ! bru%es are 9 ! neutral plane1 & ! effect ( giv+ ! bru%es ei!r positive or negative lead is to increase ! spe$1 especially ) little or no load4 ,ques4 ,:y does ! spe$ increase8 ,ans4 ,:5 ! bru%es are %ift$ f ! neutral plane1 ! rev]se voltage betwe5 ! bru%es is decreas$1 spe$ rema9+ un*ang$4 ,accord+ly1 ! pressure 9 ! supply ma9s =ces an increas$ curr5t ?r\gh ! armature ?us produc+ an increas$ armature pull :i* causes ! spe$ to increase until ! rev]se voltage rea*es a value suffici5tly l>ge to r$uce ! curr5t to ! value requir$ to supply ! necess>y driv+ torque4 ,comp\nd ,motors4--,?is type ( motor has to a c]ta9 ext5t1 ! m]its ( ! s]ies motor )\t its disadvantages1 & is adapt$ to a v>iety ( s]vice4 ,if ! curr5t fl[ 9 ! same direction ?r\gh bo? ( ! field w9d+s1 !n ! effect ( ! s]ies coil /r5g!ns t ( ! %unt coil2 ?is /r5g!n+ is great]1 ! l>g] ! armature curr5t4 ,illu/ration3 ,,fig4 #dbf4--;,comp\nd motor connections = />t+ f a di/ant po9t4 ,a comp\nd w9d+ may be us$ on motors = _m diff]5t purposes4 ,if ! curr5t fl[ 9 ! same direction ?r\gh bo? w9d+s1 !n ! effect ( ! s]ies coil /r5g!ns t ( ! %unt coil4 ,?is /r5g!n+ increases ) ! load4 ,?us ! motor gets1 at increas+ load1 a /rong] magnetic field1 & w !re=e1 if ! voltage rema9 con/ant run sl[] ?an be=e4 ,accord+ly1 = a giv5 curr5t1 ! />t+ p[] w be great] ?an t ( a %unt motor4 ,) a decreas+ load ! motor w run fa/]4 ,! comp\nd motor has1 to a c]ta9 ext5t1 ! m]its ( ! s]ies motor )\t its disadvantages4 ,by means ( comp\nd motors ! />t+ at a di/ance ) only two ma9s may be effect$1 j z 9 ! case ( ! s]ies motor4 ,! connections are %[n 9 ! diagram4 ,if ! motor be reg>d$ z be+ )\t ! %unt coil1 !n x is connect$ up exactly z ! s]ies motor 9 fig4 #daf4 ,! curr5t com+ f ! />t] ent]s ! s]ies coil at ,f1 fl[s ?r\gh ! s]ies coil & leaves x at ,e1 fl[+ f !re to ! armature bru% ,b1 ?r\gh ! armature to bru% ,a1 & f !re ?r\gh ! second ma9 back to ! g5]ator4 ,! %unt w9d+ is connect$ directly ) ! armature bru%es ,a & ,b1 & gets at />t+1 !re=e1 only a v small voltage1 h5ce its field is ne>ly ineffective4 ,b on acc\nt ( ! s]ies w9d+1 ! motor />ts z a s]ies motor4 ,obvi\sly su* a motor w n develop a v l>ge />t+ p[] l a real s]ies motor1 =1 on acc\nt ( ! l>ge space occupi$ by ! %unt coils1 !re is less space available = ! s]ies coils ?an ) a s]ies motor4 ,a comp\nd motor may1 h[ev]1 ev5 ) ?is arrangem5t1 be easily />t$1 provid$ ! load on />t+ be n too heavy4 ,:5 once runn+ ! armature w produce a rev]se voltage & ! %unt coil w be suppli$ ) ne>ly ! full t]m9al voltage4 ,ques4 ,m5tion "s *>act]i/ics ( ! comp\nd motor4 ,ans4 ,s9ce x is a comb9ation ( ! %unt & s]ies types1 x p>takes ( ! prop]ties ( bo?4 ,! s]ies w9d+ gives x /rong torque at />t+ 7?\gh n z /rong z 9 ! s]ies motor71 :ile ! pres5ce ( ! %unt w9d+ prev5ts excessive spe$4 ,! spe$ is practically con/ant "u all loads )9 ! capacity ( ! ma*9e4 ,ques4 ,describe ! connections = />t+ a comp\nd motor at a di/ance4 ,ans4 ,control at a di/ance c be effect$ ) only two wires1 j z 9 ! case ( a s]ies motor4 ,9 ! diagram fig4 #dbf1 ! curr5t com+ f ! rheo/at ent]s ! s]ies coil at ,f1 & leaves x at ,e1 !nce x fl[s to ! armature bru% ,b1 ?r\gh armature to bru% ,a1 & f "h back to ! dynamo4 ,! %unt w9d+1 :i* is connect$ across ! bru%es1 gets a v small voltage at />t+ & is accord+ly v ineffective4 ,! motor !n />ts z a s]ies motor4 ,! />t+ effect is small] ?an 9 a s]ies motor because ( ! few] turns 9 ! s]ies w9d+1 mo/ ( ! available space be+ occupi$ by ! %unt coils4 ,p[] ( a ,motor4--,! ^w p[] is def9$ z ! rate at :i* "w is done1 & is express$ z ! quoti5t ( ! "w divid$ by ! "t 9 :i* x is done1 ?us3 "w p[] ------ "t ,! diff]5ce betwe5 p[] & "w %\ld be cle>ly und]/ood4 ,"w is ! ov]com+ ( resi/ance ?r\gh a c]ta9 di/ance4 ,x is measur$ by ! product ( ! resi/ance into ! space ?r\gh :i* x is ov]come1 ?us3 "w di/ance space ,= in/ance1 9 lift+ a body f ! e>? aga9/ ! attraction ( gravity1 ! resi/ance is ! weight ( ! body1 & ! space1 ! height to :i* ! body is rais$1 ! product ( ! two be+ ! "w done4 ,! unit ( "w is ! foot p\nd1 :i* is ! am\nt ( "w done 9 ov]com+ a pressure or weight equal to "o p\nd ?r\gh "o foot ( space4 ,! unit ( p[] is ! horse p[] :i* is equal to #cc1jjj foot p\nds ( "w p] m9ute1 t is3 foot p\nds p] m9ute horse p[] ------------------------ #cc1jjj ,! unit ( p[] 0 e/abli%$ by ,james ,watt z ! p[] ( a /rong ,london draught horse to d "w dur+ a %ort int]val1 & us$ by him to measure ! p[] ( 8 /eam eng9es4 ,9 ord] to measure ! me*anical p[] ( a motor1 x is necess>y to fir/ det]m9e ! foll[+ ?ree factors ^u :i* ! p[] develop$ dep5ds3 #a4 ,pull ( ! armature1 9 p\nds2 #b4 ,di/ance 9 feet at :i* ! pull acts f ! c5t] ( ! %aft2 #c4 ,revolutions p] m9ute4 ,,example4--,if ! armature pull ( a motor hav+ a two foot pulley1 be su* t a weight ( #ejj lbs4 atta*$ to ! rim1 is j balanc$1 & ! spe$ be #a1jjj revolutions p] m9ute1 :at is ! horse p[]8 ,"h1 ! di/ance t ! pull acts f ! c5t] ( ! %aft is "o foot1 h5ce = ea* revolution ! resi/ance ( #ejj p\nds is ov]come ?r\gh a di/ance equal to ! circumf]5ce ( ! pulley or diamet] #c4adaf #b #f4bhcb feet4 ,illu/ration3 ,,fig4 #dbg4--;,g5]al ,electric type ,,cq ,motor4 ,^! motors range 9 capacity f #a_/f to #bj horse p[]4 ,! small sizes are bipol>1 & ! l>g] sizes h f\r poles4 ,= in/allations :]e ! motor is expos$ to du/1 me*anical injury or moi/ure1 x may be p>tially or entirely enclos$ by means ( h& hole cov]s4 ,! /&>d voltages are #aae1 #bcj & #eej4 ,! "w done 9 "o m9ute is express$ by ! foll[+ equation3 "w weight circumf]5ce revolutions p] 9 ( pulley p] foot p\nds m9ute lbs4 9 feet m9ute #ejj #f4bhcb #a1jjj #c1ada1fjj4 ,h5ce1 ! p[] develop$ is #c1ada1fjj #cc1jjj #ie4b horse p[]4 ,ques4 ,:at is brake horse p[]8 ,ans4 ,! net horse p[] develop$ by a ma*9e at its %aft or pulley2 s call$ because a =m ( brake is appli$ to ! pulley to det]m9e ! p[]4 ,ques4 ,describe ! app>atus us$ 9 mak+ a brake te/4 ,illu/ration3 ,fig4 #dbh4--,prony brake = det]m9+ brake horse p[]4 ,x consi/s ( a friction b& r+ :i* may be plac$ ar\nd a pulley or fly :eel1 & atta*$ to a lev] be>+ ^u ! plat=m ( a weigh+ scale 9 su* a mann] t ! friction betwe5 ! surfaces 9 contact w t5d to rotate ! arm 9 ! direction 9 :i* ! %aft revolves4 ,?is ?ru/ is resi/$ & measur$ 9 p\nds by ! scale4 ,9 sett+ up ! brake ! di/ance betwe5 ! c5t] ( ! %aft & po9t ( contact 7knife edge7 ) ! scales mu/ be accurately measur$1 ! knife edge be+ plac$ at ! same elevation z ! c5t] ( ! %aft4 ,an int]nal *annel p]mits ! circulation ( wat] ar\nd ! int]ior ( ! rim z %[n1 to prev5t ov]heat+4 ,ans4 ,te/s ( ?is k9d are usually made ) a ,prony brake z %[n 9 fig4 #dbh4 ,x consi/s ( a b& ( rope or /rip iron--! latt] is ! arrangem5t %[n--to :i* are fa/5$ a numb] ( wood5 blocks1 sev]al c>ry+ %\ld]s to prev5t ! contrivance f slipp+ (f ! :eel rim4 ,! brake b& is drawn tight1 z %[n1 s t ! blocks press aga9/ ! surface all ar\nd4 ,! brake ?us =m$ is re/ra9$ f revolv+ ) ! pulley by two arms atta*$ ne> ! top & bottom c5t]s ( ! :eels1 & jo9$ at ! opposite ends to =m a lev] :i* be>s ^u an ord9>y plat=m scale1 a suitable leg or block be+ arrang$ to keep its end level ) ! c5t] ( ! %aft4 ,by ?is arrangem5t ! am\nt ( friction betwe5 ! brake b& & ! revolv+ :eel is weigh$ ^u ! scales4 ,s9ce ! brake fits tightly en\gh to be c>ri$ ar\nd by ! :eel1 b = ! arms be>+ ^u ! scale1 ! am\nt ( frictional p[] ex]t$ by ! :eel 9 turn+ free )9 ! blocks may be transmitt$ & measur$1 j z w\ld be ! case 7 a ma*9]y load atta*$1 in/ead ( a friction brake4 ,ques4 ,:y mu/ ! po9t ( contact ( ! brake ) ! scales be level ) ! c5t] ( ! %aft8 ,ans4 ,9 ord] to det]m9e ! =ce act+ at "r angles to ! l9e jo9+ ! po9t ( contact & c5t] ( ! %aft4 ,ques4 ,:at is ! di/ance betwe5 ! c5t] ( ! %aft & po9t ( contact ) ! scales call$8 ,ans4 ,! lev] arm4 ,ques4 ,:at ?ree quantities mu/ be det]m9$ 9 a te/ 9 ord] to calculate ! brake horse p[]8 ,ans4 ,! lev] arm1 ! =ce ex]t$ on ! scales1 & ! revolutions p] m9ute4 ,ques4 ,h[ is brake horse p[] calculat$8 ,ans4 ,f ! foll[+ =mula3 ,b4 ,h4 ,p4 #b ,l ,n ,w ----------- #cc1jjj 9 :i* ,b4 ,h4 ,p4 brake horse p[]2 ,l lev] arm1 9 feet2 ,n numb] ( revolutions p] m9ute2 ,w =ce 9 p\nds at end ( lev] arm z measur$ by scales4 ,,example--,9 mak+ a brake te/ on a motor1 ! lev] arm ( ! brake is #c ft41 & ! read+ ( ! scales is #cj lbs4 ,:5 ! motor is runn+ #a1jjj revolutions p] m9ute1 :at is ! brake horse p[]8 ,sub/itut+ ! giv5 values 9 ! =mula1 #b #c #a1jjj #cj ,b4 ,h4 ,p4 --------------------- #ag4a #cc1jjj ,n[1 if ! voltmet] & ammet] read+s be #bbj & #fe respectively1 :at is ! effici5cy ( ! motor at ?is load8 ,! am\nt ( p[] absorb$ by ! motor1 or 9 o!r words1 ! input is #bbj #fe ,e4 ,h4 ,p4 -------- #ai4af #gdf & s9ce ! output is #ag4a horse p[]1 output brake horse p[] #ag4a effici5cy ------ ---------------------- ----- #hi4 input electrical horse p[] #ai4af ,spe$ ( a ,motor4--,! normal spe$ at :i* any motor w run is su* t ! sum ( ! rev]se electromotive =ce & ! drop 9 ! armature w be exactly equal to ! electromotive =ce appli$ at ! bru%es4 ,! drop 9 ! armature is ! diff]5ce betwe5 ! appli$ voltage & ! rev]se voltage4 ,mutual ,relations ( ,motor ,torque & ,spe$4--,! "* ( ! "w to be done n only det]m9es ! condition ( ! motor torque & spe$ requir$1 b also ! suitability ( a p>ticul> type ( motor = a giv5 s]vice4 ,!re are ?ree g5]al classes ( "w p]=m$ by motors1 & ^! require ! foll[+ conditions ( torque & spe$3 #a4 ,con/ant torque at v>iable spe$2 ,suitable = driv+ cranes1 hoi/s1 & elevators1 etc41 :]e ! load is con/ant & has to be mov$ at v>y+ rates ( spe$4 ,illu/ration3 ,,fig4 #dbi4--,two pa? me?od ( spe$ regulation ( s]ies motor4 ,a rheo/at is connect$ 9 %unt to ! field coils z %[n4 ,! curr5t pass+ f a to b divides betwe5 ! magnet coils & ! rheo/at coils2 ! high] ! resi/ance ( ! rheo/at ! less curr5t passes ?r\gh x1 & ! m ?r\gh ! magnet coils1 h5ce ! /rong] ! field magnet4 #b4 ,v>iable torque at con/ant spe$2 ,suitable = driv+ l9e %aft+ 9 ma*9e %ops1 :i* mu/ run at con/ant spe$ reg>dless ( v>iations ( torque due to v>iations 9 ! numb] ( ma*9es 9 op]ation at a "t1 or ! "* ( "w be+ p]=m$4 #c4 ,v>iable torque at v>iable spe$4 ,suitable = electric railway "w4 ,= example3 :5 a c> is />t$1 ! torque is at its maximum value & ! spe$ z]o1 b z ! c> ga9s headway1 ! torque decreases & ! spe$ increases4 ,spe$ ,regulation ( ,motors4--,! spe$ ( motors connect$ to con/ant voltage circuits is usually regulat$ by ! two foll[+ me?ods3 ,illu/ration3 ,,fig4 #dcj4--,v>iable field me?od ( spe$ regulation ( s]ies motor4 ,! field w9d+ is divid$ into a numb] ( sections ) leads connect+ ) swit* contact po9ts z illu/rat$4 ,! spe$ !n is regulat$ by cutt+ 9 or out ( ! circuit sections ( ! field w9d+ ?us v>y+ ! /r5g? ( ! field4 #a4 ,by ins]t+ resi/ances 9 ! armature circuit ( a %unt w\nd motor2 #b4 ,by v>y+ ! /r5g? ( ! field ( a s]ies motor4 ,! fir/ me?od is suffici5tly expla9$ "u fig4 #dah & ! second me?od is illu/rat$ 9 fig4 #dcj4 ,! controll] swit* ,s is s arrang$ t a great] or less] numb] ( field coils c be ins]t$ 9 ! field circuit4 ,:5 ! swit* arm is on po9t #a1 ! motor curr5t w fl[ ?r\gh all ! field w9d+s1 & ! /r5g? ( ! field w be at its maximum4 ,:5 ! swit* arm is mov$ s z to successively occupy positions #b1 #c1 & #d1 ?us cutt+ out ( circuit a great] & great] numb] ( field coils ! /r5g? ( ! field w be gradually decreas$ until practically all ( ! motor curr5t is l$ or wir$ ?r\gh ! armature4 ,"u ^! conditions1 :5 ! field ( a motor is at its maximum /r5g?1 ! motor torque w be at a maximum = any giv5 /r5g? ( curr5t1 & ! rev]se electromotive =ce w also be at a maximum = any giv5 spe$1 !re=e1 :5 ! field /r5g? is increas$ ! spe$ w decrease & vice v]sa4 ,ques4 ,:at results are obta9$ by ?is me?od ( regulation8 ,ans4 ,! spe$ ( a s]ies motor may be ne>ly d\bl$1 t is1 if ! l[e/ p]missible spe$ ( ! motor be #bej revolutions p] m9ute x c be readily increas$ to #ejj revolutions p] m9ute by *ang+ ! field coil connections f s]ies to p>allel4 ,x is on ?is acc\nt1 z mu* z on _! p[]ful />t+ torque1 t s]ies motors h be5 until rec5tly almo/ exclusively employ$ = electric traction purposes4 ,s]ies ,p>allel ,controll]4--,:5 two motors are us$ 9 electric railway "w1 _! armatures are connect$ 9 s]ies ) ea* o!r & an extra resi/ance :i* prev5ts ! passage ( an excessive curr5t ?r\gh ! armature be=e ! motor />ts4 ,z ! spe$ ( ! c> increases1 ! extra resi/ance is gradually cut out ( circuit & ! field w9d+ connections *ang$ f s]ies to p>allel by means ( a s]ies p>allel controll]1 :i* f9ally connects ea* motor directly across ! supply ma9s1 or betwe5 ! trolley l9e & ! track or gr\nd return4 ,effici5cy ( a ,motor4--,! comm]cial effici5cy ( a motor is ! ratio ( ! output to ! input4 ,z a rule1 ! p[] develop$ by a motor increases z ! rev]se voltage g5]at$ by x decreases1 until ?is voltage equals "o half ( ! voltage appli$ at ! bru%es4 ,aft] ?is po9t is rea*$1 ! p[] develop$ by ! motor decreases ) ! decrease ( ! rev]se voltage4 ,!re=e1 a motor p]=ms ! l>ge/ am\nt ( "w :5 its rev]se voltage is equal to "o half ! impress$ voltage4 ,illu/ration3 ,,fig4 #dca4--;,d\ble ?r[1 d\ble pole swit* = rev]s+ direction ( rotation ( a motor4 ,! direction ( rotation c be rev]s$ by *ang+ ! direction ( curr5t 9 ei!r ! armature or ! field coils4 ,x is pref]able1 h[ev]1 to rev]se ! direction ( rotation by *ang+ ! direction ( curr5t ?r\gh ! armature4 ,! swit* is wir$ z %[n1 means ( rev]sal be+ provid$ by runn+ ! wires z indicat$ by ! dott$ l9es4 ,! effici5cy ( a motor z j /at$ is ! ratio ( ! output to ! input2 ?is is equival5t to say+ t ! effici5cy ( a motor is equal to ! brake horse p[] divid$ by ! electrical horse p[]4 ,! electrical horse p[] is easily obta9$ by multiply+ ! read+s tak5 f volt met] & ammet]1 :i* gives ! watts1 & divid+ ! product by #gdf1 ! numb] ( watts p] horse p[]4 ,t is3 volts amp]es watts ,electrical horse p[] --------------- ----- #gdf #gdf ,illu/ration3 ,,fig4 #dcb4--,wir+ diagram1 %[+ electrical connections betwe5 ! armature1 field1 & int]poles ( an int]pole motor4 ,z ! "n implies1 an int]pole motor has 9 addition to ! ma9 poles1 a s]ies ( int]poles :i* are plac$ betwe5 ! ma9 poles1 & ^: function is to assi/ 9 ! rev]sal ( ! curr5t "u ! bru%es4 ,!y provide a sep>ate commutat+ field ( a correct value at all loads & spe$s1 & _! w9d+s are = ?is purpose connect$ 9 s]ies ) ! armature4 ,! prop] function+ ( ! int]poles is indep5d5t ( ! direction ( rotation ( ! armature1 also ( ! load c>ri$ ov] ! :ole spe$ range4 ,9 an ord9>y motor )\t int]poles1 commutation is assi/$ by a magnetic fr+e emanat+ f ! ma9 poles1 b z ! value ( ?is fr+e is alt]$ by ! load ( ! motor & by rheo/atic field weak5+1 if high] spe$s be desir$ f su* a ma*9e1 commutation becomes imp]fect & sp>k+ results1 mak+ a readju/m5t ( ! bru%es necess>y4 ,int]pole ,motors4--,an int]pole motor has 9 addition to ! ma9 poles1 a s]ies ( int]poles1 plac$ betwe5 ! ma9 poles4 ,! object ( ^! poles is to provide an auxili>y flux or commutat+ field at ! po9t :]e ! armature coils are %ort circuit$ by ! bru%4 ,illu/ration3 ,,figs4 #dcc to #dcg4--,p>ts ( ! type ,s int]pole motor built by ,electro-,dynamic ,co4 ,!y are z foll[s3 #a4 yoke--commutator view2 #b4 int]pole coil2 #c4 top ,r4,h4 ma9 coil2 #d4 bottom ,r4,h4 ma9 coil2 #e4 ma9 pole2 #f4 int]pole2 #g4 armature %aft1 ,r4,o4 be>+2 #h4 commutator2 #i4 armature w$ge2 #aj4 armature coil2 #aa4 bru% r+2 #ab4 bru% c>ri] insulation2 #ac4 bru% c>ri]2 #ad4 bru% gu>d2 #ae4 c>bon bru%2 #af4 bru% hold]2 #ag4 cross connect+ cable2 #ah4 oil r+2 #ai4 commutator end be>+ bu%+2 #bj4 pulley end be>+ bu%+4 ,ques4 ,:at is ! object ( ! commutat+ field produc$ by ! int]poles8 ,ans4 ,its object is to assi/ commutation1 t is1 to help rev]se ! curr5t 9 ea* coil :ile %ort circuit$ by ! bru%1 & ?us r$uce sp>k+4 ,illu/ration3 ,,fig4 #dch4--;,int]pole motor z built by ! ,electro ,dynamic ,co4 ,?is type ( motor is devis$ to prev5t sp>k+ at all loads by ! use ( int]pole magnets1 t is1 small magnets plac$ betwe5 ! field magnets4 ,! int]poles set up a field 9 a direction to /op & rev]se ! curr5t 9 ! armature coils :ile !y are %ort circuit$ by ! bru%es4 ,ques4 ,:at is ! nature ( ! commutat+ field8 ,ans4 ,! excitation ( ! int]poles be+ produc$ by s]ies turns1 ! field w v>y ) ! load1 & w1 if once adju/$ to give good commutation at any "o load1 keep ! same proportion = any o!r load1 provid$ ! iron p>ts ( ! circuit be n too highly saturat$4 ,ques4 ,/ate briefly h[ sp>k+ is r$uc$ or prev5t$ by ! action ( ! int]poles4 ,ans4 ,sp>k+ is due to self induction 9 ! coil und]go+ commutation1 :i* imp$es ! prop] rev]sal ( ! curr5t4 ,! action ( ! int]poles corrects ?is 9 t !y set up a field 9 a direction t causes a rev]sal ( ! curr5t 9 ! coil :ile x is %ort circuit$4 ,?us1 ! coil at ! in/ant x leaves ! bru%1 is n an idle coil1 b has a curr5t fl[+ 9 x 9 ! "r direction to prev5t sp>k+4 ,ques4 ,m5tion "s ( ! claims made = int]pole motors4 ,ans4 ,con/ant or adju/able spe$1 & mom5t>y ov]loads )\t sp>k+2 con/ant bru% position2 op]ation at adju/able spe$s on /&>d supply circuits ( #aaj1 #bbj1 & #ejj volts2 con/ant spe$ ) v>iable load2 rev]sal )\t *ang+ ! position ( ! bru%es4 ,,*apt] ,,xxiv ,,selection ,,& ,,in/allation ,,( ,,dynamos ,,& ,,motors ,g5]al ,conditions ,gov]n+ ,selection4--,9 any p>ticul> case1 ! voltage1 curr5t capacity1 & type ( dynamo select$ w dep5d ^u ! sy/em ( transmission or di/ribution to :i* x is to be connect$1 & ! "* ( ! "w :i* x is requir$ to p]=m4 ,! suitability ( ! diff]5t types ( dynamo = v>i\s k9ds ( "w has already be5 consid]$ to "s ext5t1 b !re are c]ta9 g5]al conditions :i* are applicable to almo/ all cases1 su* z3 #a4 ,con/ruction2 #b4 ,op]ation2 #c4 ,co/2 #d4 ,numb] & size ( units4 ,con/ruction4--,?is %\ld be z simple z possible & ( ! mo/ solid "*4 ,all p>ts %\ld be int]*angeable1 & h a good f9i%4 ,all ma*9es %\ld be provid$ ) eye bolts or o!r means by :i* !y c be lift$ or mov$1 z a :ole or 9 p>ts1 easily & )\t injury4 ,^! features are s c>efully att5d$ to & gu>ante$ by ! manufactur]s z to leave little *oice 9 ?is direction4 ,op]ation4--,! consid]ations relat+ to ! op]ation ( a ma*9e involve an exam9ation ( ! details ( its con/ruction1 9 ord] to det]m9e ! am\nt ( att5tion x w require1 ! "* ( its regulat+ device1 its capacity1 =m1 & weight4 ,ques4 ,:at may be said reg>d+ capacity8 ,ans4 ,dynamos & motors %\ld n be ov]load$1 because ! effici5cy is great] :5 ! work+ load does n exce$ ! rat$ capacity ( ! ma*9e4 ,=m4--,z a rule1 !re is n mu* *oice 9 ! matt] ( =m betwe5 /&>d ma*9es1 z !y are uni=mly symmetrical1 well proportion$ & compact4 ,x is a mi/ake1 h[ev]1 to select a light ma*9e = /ation>y use1 z ! weight ( a ma*9e increases its /r5g?1 /ability & durability4 ,co/4--,9 "s cases1 ! matt] ( fir/ co/ is important & des]ves c>eful consid]ation4 ,x %\ld be rememb]$1 h[ev]1 t high grade electric ma*9]y _c be built out ( l[ grade mat]ials & ) poor workm52 !re=e1 :5 necessity compels ! selection ( a *eap ma*9e1 x %\ld n be expect$ t its s]vice w be z satisfactory z t ( a fir/ class ma*9e4 ,numb] & ,size ( ,units4--,! be/ numb] & size ( units = an electrical plant is usually gov]n$ by ! requirem5ts ( ! driv+ eng9es4 ,z a rule1 dynamos & motors are n mu* less effici5t at qu>t] load ?an at full load1 & ! small] dynamos are fully equal to ! l>g] ma*9es 9 ?is respect1 !re=e1 a g5]at+ plant c be subdivid$1 & if s desir$1 )\t any detrim5tal results except ^? to a multiplicity ( units4 ,ques4 ,:at is ! important consid]ation ) respect to effici5cy8 ,ans4 ,effici5cy at maximum load is n s important z effici5cy at av]age load4 ,= in/ance1 9 ! diagram1 fig4 #dci1 ! rat$ effici5cy ( "o dynamo z %[n by ! curve ,a1 is #ie p] c5t41 & t ( ano!r1 z %[n by curve ,b1 is #ia p] c5t41 b x w be obs]v$ t ! av]age effici5cy ( ,b is mu* high]1 be+ #ge p] c5t4 at qu>t]-load1 #hi p] c5t4 at half-load1 & #ia p] c5t4 at ?ree-qu>t] load1 to #ee1 #gg & #hi p] c5t4 ( ,a1 at ! correspond+ loads4 ,9 ?is case1 ,a is high] ?an ,b only at full load1 & z full load is a limit :i* %\ld n be rea*$ except 9 special cases1 & !n only = %ort int]vals ( "t1 ! s]vice r5d]$ by ,b w\ld be mu* m satisfactory 9 ! long run4 ,9 ord] to avoid ! difficulties possible "u ^! conditions1 a gu>antee to c>ry #be p] c5t4 ov]load = two h\rs )\t injury %\ld be requir$1 & ei!r ?is or ! rat$ load be tak51 z ! full load1 s z to give a factor ( safety ( #be p] c5t4 ,illu/ration3 ,,fig #dci4--;,effici5cy curves = #ajj ,k4 ,w4 dynamos4 ,! effici5cy ( a dynamo at maximum load is n s important z at av]age load4 ,= in/ance1 if 9 ! figure ! curve ,o ,b ,c repres5t ! effici5cy ( a #ajj ,k4 ,w4 dynamo & ,o ,a ,d1 t ( ano!r ma*9e1 x w\ld be 9 accordance ) common practice to comp>e !m at rat$ load1 at :i* ! effici5cy ( ! fir/ is only #ia1 :ile ! o!r is #ic4 ,! fir/ ma*9e1 h[ev]1 is f> bett] ?an ! second1 s9ce its av]age effici5cy is mu* high]1 be+ ne>ly #ia betwe5 half load & #be ov]load4 ,x %\ld be not$ t full load is a limit :i* %\ld be b occasionally rea*$1 & !n only = %ort p]iods ( "t4 ,ques4 ,^u :at does ! *oice ( field w9d+ ( a dynamo dep5d8 ,ans4 ,! diff]5t classes ( field w9d+ h already be5 discuss$1 b 9 g5]al ! conditions gov]n+ selection are z foll[s3 ,! s]ies dynamo is us$ :]e a con/ant curr5t at v>iable voltage is desir$1 z 9 s]ies arc lamp circuits4 ,a %unt dynamo is us$ on con/ant voltage circuits1 :]e ! di/ance f ! ma*9e to ! load is n great1 t is1 :]e !re is small l9e loss4 ,) a comp\nd dynamo !re is comp5sation = l9e loss1 t is1 x c be con/ruct$ s t ! voltage at its t]m9als1 or at ! load c be ma9ta9$ con/ant or all[$ to increase or decrease ) a *ange 9 load4 ,x c ?us op]ate lamps at con/ant voltage ?\gh !y be locat$ at "s di/ance1 or ! voltage at ! end ( ! l9e c be made to increase ) an increase ( load1 z is frequ5tly ! case 9 railway "w4 ,illu/ration3 ,,fig4 #ddj4--;,holz]-,cabot p]=mance curves ( /&>d #bj ,h4 ,p4 motor1 %[+ effici5cy1 spe$ regulation1 & amp]es input4 ,ques4 ,= :at conditions ( s]vice are s]ies motors adapt$8 ,ans4 ,!y are us$ on con/ant curr5t circuits1 & also on con/ant voltage circuits z 9 railway "w & simil> purposes :]e an att5dant is always at h& to regulate ! spe$4 ,ques4 ,"n "s advantages & disadvantages ( s]ies motors4 ,ans4 ,!y are easily />t$ ev5 "u heavy loads1 ! w9d+ is *eap] ?an ! o!r types & ! spe$ is ne>] con/ant ?an %unt motors :5 op]at$ on con/ant curr5t circuits4 ,:5 us$ on con/ant pressure circuits1 su* z is employ$ = inc&esc5t light+1 ! spe$ w dep5d on ! load4 ,ques4 ,:at k9d ( circuit is suitable = %unt motors8 ,ans4 ,!y are us$ on con/ant voltage circuits4 ,ques4 ,:at are ! advantages ( %unt motors8 ,ans4 ,! spe$ rema9s ne>ly con/ant = v>iable load4 ,ques4 ,/ate ! disadvantages4 ,ans4 ,!y />t less easily "u a heavy load ?an d s]ies motors1 & ! spe$ _c be v>i$ ?r\gh any wide range )\t consid]able loss4 ,! %unt motor requires m att5tion ?an ! s]ies type & is m liable to be burnt out4 ,location4--,! place *os5 = ! dynamo or motor %\ld be dry1 free f du/1 & pref]ably :]e a cool curr5t ( air c be _h4 ,x %\ld all[ suffici5t room = a belt ( prop] l5g? :5 a belt drive is us$4 ,f\ndations4--,x is mo/ important to secure a good f\ndation = e dynamo1 & great c>e %\ld be tak5 to h !m entirely sep>ate f ^? ( ! walls ( ! build+ 9 :i* ! ma*9e is in/all$1 & if ! dynamo be directly driv51 b n on ! same b$ plate z ! eng9e1 a f\ndation l>ge en\gh = bo? toge!r %\ld be laid d[n4 ,/one or concrete may be us$1 or brick built ) cem5t1 hav+ a l>ge ?ick /one b$d$ at ! top4 ,= small ma*9es ! hold+ d[n bolts may be set ) lead or sulphur 9 holes 9 ! /one top1 b = l>ge ma*9es ! bolts %\ld be long en\gh to pass d[n to ! bottom1 :]e !y %\ld be an*or$ ) iron plates4 ,sett+ up ( ,dynamos & ,motors4--,9 unpack+ ! ma*9es c>e %\ld be tak5 to avoid injury to any "p1 & 9 putt+ ! p>ts toge!r1 ea* "p %\ld be c>efully clean$1 & all ! p>ts put toge!r 9 exactly ! "r way4 ,! %afts1 be>+s1 magnetic jo9ts1 & electrical connection %\ld receive especial att5tion & be ?or\ghly clean$ ( e p>ticle ( dirt1 grit1 du/1 metal clipp+s1 etc4 ,ques4 ,:o %\ld pref]ably assemble ! ma*9es8 ,ans4 ,:5ev] possible1 !y %\ld be assembl$ by someone ?or\ghly famili> ) ! con/ruction2 b if ! s]vices ( su* a p]son _c be _h1 no "o %\ld attempt to put a ma*9e toge!r unless he has a draw+ or photograph ( ! same = a g5]al guide4 ,ques4 ,:at precaution %\ld be tak5 ) ! armature8 ,ans4 ,x %\ld be h&l$ c>efully to avoid any injury to ! wires ( ! w9d+ & _! insulation4 ,if x become necess>y to lay ! armature on ! gr\nd x %\ld be laid on clean pap] or clo?1 b x is bett] to support x by ! %aft on two wood5 horses or o!r supports1 & ?us avoid any /ra9 on ! armature body or commutator4 ,illu/ration3 ,,fig4 #dda4--;,f\ndation4 ,x may be made ei!r ( concrete1 /one or brick4 ,! ma*9]y is held firmly 9 place on ! f\ndation by an*or bolts built into x2 ! prop] position = ! bolts are det]m9$ by a wood5 template susp5d$ above ! f\ndation z %[n4 ,! bolts are surr\nd$ by iron pipe t fixes !m v]tically b p]mits a little side play to all[ = any slight errors 9 locat+ ! c5t]s on ! template4 ,connect+ ,up ,dynamos4--,! mann] 9 :i* ! connections ( ! field magnet coils1 bru%es1 & t]m9als1 are connect$ to "o ano!r dep5ds entirely ^u ! type ( ma*9e4 ,! field magnet %unt coils ( %unt & comp\nd w\nd dynamos1 are inv>iably arrang$ 9 s]ies ) "o ano!r1 & !n connect$ z a %unt to ! bru%es or t]m9als ( ! ma*9e4 ,! s]ies coils ( s]ies & comp\nd w\nd ma*9es are arrang$ ei!r 9 s]ies or 9 p>allel ) "o ano!r1 accord+ to conditions ( op]ation1 & !n connect$ 9 s]ies to ! armature & ext]nal circuit4 ,c\pl+ ,up ,field ,magnet ,coils4--,9 c\pl+ up ! coils ( ei!r sali5t or consequ5t pole field magnets1 assume ea* ( ! pole pieces to h a c]ta9 pol>ity 79 bipol> dynamos two poles only1 a nor? & s\? pole respectively1 are requir$2 9 multipol> dynamos ! poles mu/ be arrang$ 9 alt]nate ord] ar\nd ! armature1 ! numb] ( ,n & ,s poles be+ equal71 !n apply ,flemm+'s rule z giv5 "u fig4 #acb1 to ea* ( ! coils1 & asc]ta9 ! direction 9 :i* ! magnetiz+ curr5t mu/ fl[ 9 ea* 9 ord] to produce ! assum$ pol>ity 9 ea* ( ! pole pieces4 ,hav+ m>k$ ^! directions on ! coils1 !y c be c\pl$ up 9 ei!r s]ies or p>allel connection accord+ to requirem5ts1 s t ! curr5t fl[s 9 ! prop] direction 9 ea*4 ,illu/ration3 ,,fig4 #ddb4--;,comp>ison ( space occupi$ by direct & belt connect$ dynamos4 ,9 (fice build+s space is ( value & ! room requir$ by belt connect$ dynamos c always be put to pr(itable use4 ,= ?is reason ! direct connect$ unit has become g5]ally adopt$ 9 ! be/ type ( (fice build+s4 ,9 l>ge factories ! direct connect$ unit is g5]ally adopt$ also to save space4 ,:]e ^! conditions d n obta91 belt$ type ( dynamo c be us$ to advantage z a giv5 output c be obta9$ ) a small] size ma*9e ?an :]e x is direct connect$ to ! eng9e4 ,?is is due to ! limit$ rotative spe$s at :i* eng9es c be run4 ,! illu/ration %[s ! relative space requir$ by ! two types4 ,! ,drive4--,v>i\s means are employ$ to connect ! eng9e or o!r prime mov] ) ! dynamo1 or ! motor ) ! ma*9]y to driv]4 ,among ^! may be m5tion$ ! foll[+3 #a4 ,direct drive2 #b4 ,belt drive2 #c4 ,rope drive2 #d4 ,ge> drive2 #e4 ,friction drive4 ,illu/ration3 ,,fig4 #ddc4--;,g5]al ,electric type ,m ,p1 m>9e g5]at+ set ) t&em comp\nd eng9e4 ,! requirem5ts ( su* units are compactness1 light weight1 simplicity1 fre$om f vibration & noise at high spe$1 p]fect regulation & durability4 ,by adopt+ a %ort /roke = ! eng9es & a special armature w9d+ = ! dynamos1 ! height & l5g? ( ! sets h be5 r$uc$4 ,! b$ is c>ri$ out to ! full wid? ( ! dynamo frame1 mak+ an ample base surface = f\ndation )\t increas+ ! floor space requir$4 ,:ile ! con/ruction gives a massive appe>ance1 ! b$ has be5 cor$ out & ! v>i\s p>ts s design$ t ! complete sets h an approximate capacity ( #c watts p] p\nd4 ,all ( ! mov+ p>ts are enclos$ by ! eng9e column1 exclud+ du/ & r$uc+ we> & att5tion to a m9imum4 ,! be>+ are oil$ automatically "u pressure4 ,^! sets are made 9 sizes f #be ,k4 ,w4 to #ge ,k4 ,w41 ! cyl9d] dim5sions = ! smalle/ size be+ #f & #aj by #e1 & = ! l>ge/ size #aj & #ah by #h4 ,s+le cyl9d] sets are made 9 sizes rang+ f #b ,k4 ,w4 to #ej ,k4 ,w41 ! cyl9d] dim5sions rang+ f #c #c to #ab #aa4 ,see fig4 #gcj4 ,ques4 ,:at is a direct drive8 ,ans4 ,"o 9 :i* ! driv+ memb] is connect$ direct to ! driv5 memb]1 )\t any int]pos$ ge>+4 ,fig4 #ddc %[s a direct connect$ unit1 :i* is an example ( direct drive4 ,ques4 ,:at may be said ) respect to direct drive8 ,ans4 ,x is ! simple/ me?od & ! space requir$ is less ?an ) belt drive4 ,) direct drive ! eng9e & dynamo mu/ run at ! same spe$2 ?is is a disadvantage because ! desirable spe$s ( ! two ma*9es may n agree4 ,s9ce ! usual eng9e spe$s are sl[] ?an dynamo spe$s1 direct drive involves ! use ( a l>g] dynamo = a giv5 output ?an w\ld be necess>y ) belt connection1 & involves a correspond+ increase 9 co/ & great] friction loss due to ! rotation ( l>g] & heavi] p>ts4 ,illu/ration3 ,,fig4 #ddd4--;,belt clamp = /ret*+ belt & hold+ ! ends :ile mak+ jo9t4 ,x consi/s ( a /ret*+ frame1 ! two ends ( :i* are c\pl$ by screw$ b>s2 us$ = pull+ ! ends ( a belt toge!r ) ! prop] t5sion1 :5 lac+ or jo9+ ! ends4 ,ques4 ,m5tion "s ( ! features ( belt drive4 ,ans4 ,great] flexibility 9 ! orig9al design ( a plant is possible & new arrangem5ts ( old app>atus c be made at any "t4 ,x gives conv5i5tly any desir$ spe$ ratio & p]mits ! use ( high spe$ dynamos & motors4 ,ques4 ,/ate "s ( ! disadvantages ( belt drive4 ,ans4 ,consid]able space is requir$ & ! action is n positive4 ,belts ex]t a side pull on ! be>+s :i* results 9 we>1 also loss ( p[] by friction4 ,illu/ration3 ,,figs4 #dde & #ddf4--,two me?ods ( lac+ a belt4 ,9 fig4 #dde two r[s ( oval holes %\ld be made ) a pun*1 z indicat$4 ,! ne>e/ hole %\ld be in* f ! side1 & ! fir/ r[ #g_/h in* f ! end1 & ! second r[ #a in*es f ! end ( ! belt4 ,9 l>ge belts ^! di/ances %\ld be a little great]4 ,a regul> belt lac+ 7a /rong1 pliable /rip ( lea!r7 %\ld be us$1 beg9n+ at hole ,no4 #a1 & pass+ consecutively ?r\gh all ! holes z numb]$4 ,9 fig4 #ddf ! holes are all made 9 a r[4 ,?is me?od has ! advantage ( mak+ ! lac]s lie p>allel ) ! motion on ! pulley side4 ,! lac+ is d\bl$ to f9d its middle1 & ! two ends are pass$ ?r\gh ! two holes m>k$ #a & #a;a precisely z 9 lac+ a %oe4 ,! two ends are !n pass$ successively ?r\gh ! two s]ies ( holes 9 ! ord] 9 :i* !y are numb]$1 #b1 #c1 #d1 etc41 & #b;a1 #c;a1 #d;a1 etc41 f9i%+ at #ac & #ac;a1 :i* are additional holes = fa/5+ ! ends ( ! lac]4 ,ques4 ,give a rule = det]m9+ ! prop] size ( belt4 ,ans4 ,a s+le belt travell+ #a1jjj feet p] m9ute w transmit "o horse p[] p] in* ( wid?2 a d\ble belt w transmit twice ?is am\nt4 ,,example4--,:at size ( d\ble belt is requir$ to transmit #ej horse p[] at #d1jjj ft4 spe$1 & :at diamet] pulley mu/ be us$ = #ied revolutions p] m9ute at #d1jjj ft4 spe$ ( belt8 ,illu/ration3 ,,fig4 #ddg4--,wrong way to run a belt4 ,! pull %\ld n come on ! top side1 because1 ) slack at bottom !re is a t5d5cy to slip4 ,! horse p[] transmitt$ p] in* is #d1jjj ----- #b #h #a1jjj accord+ly1 ! wid? ( belt requir$ to transmit #ej horse p[] is #ej #h #f4be1 say #f4 ,= #d1jjj ft4 p] m9ute belt spe$1 ! di/ance 9 in*es travell$ by ! belt p] revolution ( ! pulley4 #d1jjj #ab ---------- #ej4ca in*es #ied ,?is is equal to ! circumf]5ce ( ! pulley1 & ! correspond+ diamet] is #ej4ca ---------- #af4a1 say #af in*es4 ,ques4 ,:at is ! prop] spe$ = a belt8 ,ans4 ,f #c1jjj to #e1jjj feet p] m9ute1 dep5d+ on conditions4 ,po9ts ,relat+ to ,belts4 #a4 ,! am\nt ( p[] t a belt ( giv5 size c transmit is n a v def9ite quantity4 ,! rule j giv5 is cons]vative & w give an amply l>ge belt = ord9>y conditions4 #b4 ,a belt %\ld make a /raight run ?r\gh ! air & ov] ! pulleys )\t wabbl+2 x %\ld ma9ta9 an ev5 & p]fect contact ) t "p ( ! pulley ) :i* x comes 9 contact4 ,9 ord] to d ?is x %\ld be kept s(t1 pliable1 & h no abrasions or r\gh places4 ,illu/ration3 ,,fig4 #ddh4--,"r way to run a belt4 ,! pull %\ld come on ! l[] side br++ ! slack on top4 #c4 ,:5 belt fa/5]s give way !re is too mu* /ra9 ^u belt4 ,! greate/ am\nt ( slack 9 a belt is f\nd :]e x leaves ! driv+ pulley1 h5ce ! tight5] %\ld be ne> ! driv+ pulley1 z x takes up ! slack1 prev5ts vibration & dim9i%es /ra9 on belts & be>+s4 ,m ?an #ajj degrees ( heat is injuri\s to belts4 #d4 ,d\ble belts %\ld always run ) ! splices1 & n aga9/ !m4 ,qu>t] turn belts %\ld be made ( two ply lea!r1 s z to dim9i% ! side /ra94 #e4 ,friction is greate/ :5 ! pulleys are cov]$ ) lea!r4 ,friction dep5ds ^u pressure1 b adhesion dep5ds ^u surface contact2 ! m a belt adh]es to pulley surface )\t /ra9+1 ?r\gh too mu* tight5+1 ! bett] ! driv+ p[]4 ,slipp+ occurs on wet days because ! lea!r absorbs dampness4 #f4 ,a lea!r cov]$ pulley w produce m resi/ance ?an poli%$ or r\gh iron ones4 ,a good belt dress+ makes a smoo?1 resi/+ surface1 & z x conta9s no oils :i* create a slipp]y surface to belts1 x increases belt adhesion4 ,! friction ( lea!r ^u lea!r is five times great] ?an lea!r ^u iron4 #g4 ,moi/ure & wat] di/5d ! fibres1 *ange ! prop]ties ( ! tann]'s grease & s(t5+ comp\nds4 ,repeat$ saturation & dry+ w soon de/roy lea!r4 ,lea!r well fill$ ) tann]'s grease or animal oil1 if all[$ to hang 9 a w>m room = sev]al mon?s )\t h&l+1 w dry out1 become h>%1 & w readily crack4 #h4 ,a runn+ belt is /ret*$ & relax$ at diff]5t times & unless !re be p]fect ela/icity 9 all its p>ts !re w n be uni=m di/5sion4 #i4 ,!re %\ld be #be p] c5t4 m>g9 all[$ = adhesion be=e a belt beg9s to slip4 ,illu/ration3 ,,figs4 #ddi to #dea4--,me?od ( align+ eng9e & dynamo4 ,9 fig4 #ddi1 a l9e is /ret*$ f ,a to ,e & ! dynamo %ift$ until ! l9e contacts ) po9ts ,a1 ,d1 ,i1 & ,e4 ,9 a small dynamo1 ! pulley may be loos5$ & set back on ! %aft z 9 fig4 #dej1 :ile l9+ up ! faces1 & !n mov$ back to its orig9al position z 9 fig4 #dea4 ,:5 ! pulley is n easily %ift$ ! di/ances at ,a & ,d 7fig4 #ddi7 may be measur$4 ,rules = ,calculat+ ,spe$ & ,sizes ( ,pulley4--,:5 two pulleys are work+ toge!r connect$ by a belt1 ! "o :i* communicates ! motion is call$ ! driv] & ! o!r :i* receives x1 ! driv5 pulley4 ,to ,f9d ! ,size ( ! ,driv+ ,pulley3 ,multiply ! diamet] ( ! driv5 pulley by its requir$ numb] ( revolutions1 & divide ! product by ! revolutions ( ! driv]4 ,! quoti5t w be ! diamet] ( ! driv]4 ,to ,f9d ! ,numb] ( ,revolutions ( ! ,driv5 ,pulley3 ,multiply ! diamet] ( ! driv] by its numb] ( revolutions1 & divide by diamet] ( driv54 ,! quoti5t w be ! numb] ( revolutions ( ! driv54 ,to ,f9d ! ,diamet] ( ! ,driv5 t %all ,make a ,giv5 ,numb] ( ,revolutions1 ! ,diamet] & ,revolutions ( ! ,driv] ,be+ ,giv53 ,multiply ! diamet] ( ! driv] by its numb] ( revolutions1 & divide ! product by ! numb] ( revolutions ( ! driv5 pulley4 ,! quoti5t w be ! diamet] ( ! driv5 pulley4 ,rope ,drive4--,9 ?is me?od ( p[] transmission1 rope is run 9 ,v-%ap$ grooves 9 ! rims ( ! pulleys2 ?is =m ( drive1 9 "s cases1 is m desirable ?an o!rs4 ,illu/ration3 ,,fig4 #deb4--;,g5]al ,electric ,c ,q back ge>$ motor driv+ ,hamilton s5sitive drill4 ,:5 sl[ly mov+ ma*9es are to be driv51 or :]e1 = any reason1 v mod]ate belt spe$s are requir$1 ! back ge>$ motor is desirable4 ,two ratios ( ge> r$uction h be5 adopt$ z /&>d2 !y are3--#d to #a & #h to #a4 ,ques4 ,:at are "s ( ! advantages ( rope drive8 ,ans4 ,m p[] c be transmitt$ ) a giv5 diamet] & wid? ( pulley1 on acc\nt ( ! increas$ grip 9 ! grooves4 ,rope drive c be employ$ = long or %ort di/ances by reason ( its lightness & ! action ( ! grooves4 ,ge> ,drive4--,?is me?od is us$ :]e a positive drive is desir$1 z = elevator or railway motors4 ,x admits ( any degree ( spe$ r$uction )\t att5d+ difficulties z w\ld be enc\nt]$ ) belt drive4 ,?us1 ) ! worm type ( ge> z us$ on elevator motors a great r$uction 9 velocity c be made )\t incurr+ ! exp5se ( c\nt]%aft z ) a belt4 ,illu/ration3 ,,fig4 #dec4--,watson v]tical motor design$ to op]ate a v]tical %aft1 ei!r ?r\gh belt connection1 or by direct drive4 ,hess-,bright ball be>+s are us$1 tak+ ! d[nw>d ?ru/ due to ! weight ( ! armature4 ,= m\nt+ on ! floor or ceil+1 a tripod base 7z %[n7 is furni%$1 ! /&>d slid+ base be+ us$ on a side wall4 ,! armature %aft may be ext5d$ = pulley or c\pl+ ei!r above or bel[ ! motor4 ,friction ,drive4--,?is is a v simple mode ( transmitt+ p[] & has ! advantages ( simplicity & compactness4 ,9 op]ation1 ! driv+ :eel is press$ aga9/ ! :eel to be driv51 transmitt+ motion to ! latt] by ! frictional grip4 ,! drive is ?r[n out ( ge> by slightly mov+ ! ma*9e on its slid+ base4 ,9 con/ruction1 ! friction may be increas$ by mak+ "o :eel ( ! pair ( wood1 compress$ pap]1 or lea!r4 ,electrical ,connections4--,circuits = dynamos & motors %\ld be c>efully plann$ s z to secure ! simple/ arrangem5t1 & to avoid unnecess>y exp5se & delay1 ! wir+ %\ld be in/all$ 9 accordance ) ! requirem5ts ( ! ,national ,electrical ,code4 ,illu/ration3 ,,fig4 #ded4--,sl+ = h&l+ armatures4 ,9 rais+ an armature x %\ld be support$ by ! %aft to avoid any /ra9 on ! armature body or commutator4 ,ques4 ,:at may be said ) respect to expos$ & conceal$ wir+8 ,ans4 ,expos$ wir+ is *eap & accessible2 a %ort circuit or gr\nd is easily locat$ & repair$4 ,conceal$ wir+1 especially :5 plac$ "u ! floor1 has ! advantage ( be+ out ( ! way1 & ?us protect$ f injury4 ,ques4 ,9 wir+ a dynamo :at are ! consid]ations ) respect to size ( wire8 ,ans4 ,all conductors1 includ+ ^? connect+ ! ma*9e ) ! swit*bo>d1 z well z ! bus b>s on ! latt]1 %\ld be ( ample size to be free f ov]heat+ & excessive loss ( voltage4 ,! drop betwe5 ! g5]ator & swit*bo>d %\ld n exce$ "o-half p] c5t4 at full load1 because x int]f]es ) prop] regulation & adds to ! less easily avoid$ drop on ! di/ribution sy/em4 ,,*apt] ,,xxv ,,auxili>y ,,app>atus ,!re are num]\s devices t mu/ be us$ 9 connection ) dynamos & motors = prop] control & safe op]ation4 ,among ^! may be m5tion$3 #a4 ,swit*es2 #b4 ,fuses2 #c4 ,circuit break]s2 #d4 ,rheo/ats2 #e4 ,swit*bo>ds4 ,swit*es4--,a swit* is a device by means ( :i* an electric circuit may be op5$ or clos$4 ,!re are num]\s types ( swit*2 !y may be ei!r s+le or multi-pole1 s+le or d\ble ?r[ & ei!r ( ! snap or knife =m4 ,ques4 ,:at is ! diff]5ce betwe5 a s+le & d\ble pole swit*8 ,ans4 ,a s+le pole swit* controls only "o ( ! wires ( ! circuit1 :ile a d\ble pole swit* controls bo?4 ,ques4 ,:at is ! diff]5ce betwe5 a s+le break & a d\ble break swit*8 ,ans4 ,! di/9ction is t ! "o breaks ! circuit at "o po9t only1 :ile ! o!r breaks x at two po9ts4 ,ques4 ,:at is ! advantage ( a d\ble break8 ,ans4 ,if ! circuit be op5$ at two po9ts 9 s]ies at ! same in/ant1 ! electromotive =ce is divid$ betwe5 ! two breaks & ! l5g? to :i* ! curr5t w ma9ta9 an arc at ei!r break is r$uc$ to "o-half2 ?us !re is less *ance ( burn+ ! metal ( ! swit*4 ,ano!r reason = provid+ two breaks is to avoid us+ ! blade pivot z a conductor1 ! contact at ?is po9t be+ too poor = good conductivity4 ,illu/ration3 ,,figs4 #dee to #deg4--;,adam's s+le ?r[ knife swit*es )\t fuse connections4 ,fig4 #dee1 s+le pole swit*2 fig4 #def1 d\ble-pole swit*2 fig4 #deg1 ?ree-pole swit*4 ,illu/ration3 ,,figs4 #deh to #dfj4--;,adam's s+le ?r[ knife swit*es ) fuse connections at ! h&le end4 ,fig4 #deh1 s+le pole swit*2 fig4 #dei1 d\ble pole swit*2 fig4 #dfj1 ?ree pole swit*4 ,ques4 ,:5 %\ld a knife swit* be us$8 ,ans4 ,:5 ! capacity ( ! circuit 9 :i* x is to be plac$ exce$s #aj amp]es4 ,ques4 ,describe a knife swit*4 ,ans4 ,fig4 #dfa illu/rates a knife swit* ( ! d\ble pole1 s+le ?r[ type4 ,x consi/s ( ! foll[+ p>ts3 base1 h+es1 blades1 contact jaws1 insulat+ cross b>1 & h&le1 z %[n4 ,ques4 ,h[ %\ld knife swit*es be in/all$8 ,ans4 ,!y %\ld be plac$ s t gravity t5ds to op5 !m4 ,o!rwise if ! h+es become loose1 ! weight ( ! blades & h&le w\ld t5d to close ! swit*1 ?us clos+ ! circuit & possibly result+ 9 consid]able damage4 ,illu/ration3 ,,fig4 #dfa4--;,a s+le ?r[1 two pole knife swit*4 ,z usually con/ruct$ x is made ( h>d drawn copp] ) ca/ t]m9al lugs & fibre cross b>4 ,ques4 ,h[ %\ld swit*es be proportion$8 ,ans4 ,! m9imum area ( ! contact surfaces %\ld n be less ?an 4#ja squ>e in* p] amp]e1 & 9 ^? us$ on arc light+ or o!r high voltage circuits :]e ! curr5t is usually small1 ! area ( ! contact surfaces are usually f 4#jb to 4#je in* p] amp]e4 ,s9ce dirt or oxidation w\ld prev5t good contact "u a simple pressure betwe5 ! contact surfaces1 ! me*anism ( a swit* provides a slid+ contact4 ,9 ! g5]al design ( swit*es1 all p>ts :i* c>ry curr5t are giv5 a cross sectional area ( at lea/ "o squ>e in* p] #a1jjj amp]es if !y be made ( copp]1 & ab\t ?ree times z mu* if made ( brass1 z ! conductivity ( ! latt] is only "o-?ird t ( ! =m]4 ,fur!rmore1 ! curr5t %\ld nev] be p]mitt$ to pass ?r\gh spr+s1 z ! heat g5]at$ w de/roy _! ela/icity4 ,illu/ration3 ,,fig4 #dfb4--,triple pole1 d\ble break d\ble ?r[ knife swit* = v heavy curr5t4 ,! blades are made up ( num]\s /rips to give adequate contact area4 ,a d\ble ?r[ swit* is us$ :5 x is desirable to op5 "o circuit & imm$iately close ano!r1 or to transf] "o or m connections f "o circuit to ano!r 9 ! lea/ practical int]val ( "t1 also1 :5 "o connection is to be brok5 & ano!r clos$ & x is undesirable to all[ bo? to be clos$ at ! same "t4 ,ques4 ,:at difficulty is exp]i5c$ 9 op5+ a circuit 9 :i* a heavy curr5t is fl[+8 ,ans4 ,x is impossible to in/antly /op ! curr5t by op5+ ! swit*1 consequ5tly ! curr5t cont9ues to fl[ & mom5t>ily jumps ! air gap1 result+ 9 a m or less int5se arc :i* t5ds to burn ! metal ( ! swit*4 ,ques4 ,h[ is ?is rem$i$ to "s ext5t8 ,ans4 ,! contact pieces are s %ap$ t !y op5 along _! :ole l5g? at ! same "t1 s z to prev5t ! conc5tration ( ! arc at ! la/ po9t ( contact4 ,?is feature is cle>ly %[n 9 fig4 #dfa4 ,illu/ration3 ,,fig4 #dfc4--;,a quick break knife swit* ( ! s+le ?r[1 s+le break1 "o pole1 type4 ,! contact blade is held betwe5 ! jaws by _! clamp+ friction until ! h&le compresses ! spr+ suffici5tly to =ce ! blade out4 ,z soon z x breaks contact ) ! jaws1 ! spr+ exp&s & drives ! blade away f ! jaws ) great] rapidity ?an c\ld be done by h&4 ,! object ( ?is action is to break ! arc z quickly z possible to prev5t burn+ ! metal ( ! swit*4 ,illu/ration3 ,,figs4 #dfd & #dfe4--,snap swit*2 views %[+ swit* ) cov] on1 & expos$ to %[ me*anism4 ,! swit* is provid$ ) indicat+ dial :i* regi/]s on & (f positions4 ,,fig4 #dff4--;,gas ,eng9e snap swit*4 ,! fir/ snap makes connection s t ignit] is run f /orage batt]y2 second snap connections are *ang$ s t ignit] is suppli$ f dynamo2 ?ird snap makes connections s t dynamo supplies ignit] & *>ges /orage batt]y2 f\r? snap1 all (f4 ,ques4 ,= :at s]vice are snap swit*es suitable8 ,ans4 ,!y are us$ on circuits conta9+ lamps 9 comp>atively small gr\ps1 & o!r light duty s]vice4 ,ques4 ,:at is a quick break swit*8 ,ans4 ,a =m ( swit* 9 :i* ! contact pieces are snapp$ ap>t by ! action ( ! spr+s1 z %[n 9 fig4 #dfc1 s z to make ! duration ( ! arc z %ort z possible4 ,! curr5t all[$ 9 ea* bran* circuit ( an electric light+ sy/em is limit$ by ! insurance rules to a maximum ( #ffj watts equival5t to #ab lamps ( #af c4p4 ea* at #aaj volts4 ,!y are also employ$ to control lamps 9 gr\ps 9 !atres & o!r places :]e _m lamps are turn$ on or (f at ab\t ! same "t4 ,illu/ration3 ,,fig4 #dfg4--,spool ( fuse wire4 ,! wire is usually made ( an alloy ( t9 & lead1 su* z half & half sold]4 ,bismu? is frequ5tly add$ to ! alloy to l[] ! melt+ po9t ,= half & half sold] ! melt+ po9t is #cgj ,fahr4 ,! quickness ) :i* a fuse w melt aft] ! curr5t has rea*$ ! limit dep5ds ^u ! specific heat & lat5t heat ( ! metal4 ,! curr5t requir$ to bl[ a fuse increases some:at ) ! age ( ! fuse ow+ to oxidation & molecul> *anges4 ,fuses are sometimes rat$ accord+ to ! numb] ( amp]es to be tak5 normally by ! circuit !y are to protect4 ,?us1 a #aj amp]e fuse is suppos$ to protect a circuit ^: regul> curr5t %\ld n exce$ #aj amp]es1 & to bl[ if ! curr5t rise to say #ab amp]es4 ,! ,und]writ]s' rule requires t ! rat+ be ab\t #hj ( ! maximum curr5t x c c>ry indef9itely1 ?us all[+ ab\t #be ov]load be=e ! fuse melts4 ,! fus+ curr5t v>ies consid]ably accord+ to circum/ances4 ,! temp]ature ( ! surr\nd+ air or o!r sub/ances affects ! melt+ curr5t greatly1 because ! rate at :i* heat f ! fuse w be transf]r$ to ! surr\nd+s dep5ds ^u ! diff]5ce ( temp]ance betwe5 !m & ! fuse4 ,h5ce a fuse 9 a w>m place w be melt$ by a small] curr5t ?an a simil> fuse 9 a cold place4 ,= a simil> reason1 a fuse 9 an enclos$ place :]e !re is little *ance = ! heat to be dissipat$1 w melt ) a small] curr5t ?an ! same 9 an op5 place4 ,if ! curr5t increase gradually to t :i* w\ld ord9>ily melt ! fuse1 ! high temp]ature makes ! fuse wire oxidize rapidly2 ?is sometimes makes a sort ( tube ( oxide :i* w n break ev5 aft] ! fuse wire inside has melt$1 & s ! fuse c>ries m ?an its rat$ curr5t4 ,op5 fuses are s unreliable t circuit break]s are pref]able = l>ge curr5ts2 :5 fuses are us$1 ! enclos$ type z %[n 9 figs4 #dfh to #dgj1 is usually ! m desirable4 ,fuses4--,all circuits subject to abnormal increase ( curr5t :i* might ov]heat ! sy/em1 %\ld be protect$ by fuses :i* w melt & ?us op5 ! circuit4 ,a fuse is simply a /rip ( fusible metal1 (t5 consi/+ ( lead ) a small p]c5tage ( t91 connect$ 9 s]ies 9 ! circuit4 ,exp]im5ts h %[n t = l>ge fuses1 a multiple fuse is m s5sitive ?an a s+le "o4 ,a "o hundr$ amp]e fuse may be made by tak+ f\r wires ( tw5ty-five amp]es capacity4 ,a fuse block may be ov]load$1 n because ! metal ( ! t]m9als is n ( suffici5t cross section to c>ry ! curr5t1 b because ( insuffici5t area (1 contact1 or loose contact ( fuse & wires2 ! ov]load ?us caus$ results 9 heat+ & frequ5tly melts ! fuse4 ,illu/ration3 ,,figs4 #dfh to #dgj4--;,d ,w1 enclos$ c>tridge fuses4 ,fig4 #dfh1 type = #c to #fj amp]es2 fig4 #dfi1 type = #fa to #ajj amp]es2 fig4 #dgj1 type = #aja to #a1jjj amp]es4 ,ques4 ,:]e %\ld fuses be plac$8 ,ans4 ,!y %\ld be ins]t$ :]ev] ! size ( wire *anges or :]ev] !re is a bran* ( small] size wire connect$1 unless ! next fuse on ! ma9 or l>g] wire is small en\gh to protect ! bran* or small wire4 ,illu/ration3 ,,figs4 #dga to #dgh4--;,int]ior con/ruction ( ,d4 ,w4 fuses4 ,9 ! manufacture ( ^! fuses1 f\r types ( fuse l9k are us$ accord+ to capacity ( fuse1 & classifi$ z3 #a1 air drum l9k2 #b1 flat l9k2 #c1 multiple l9k2 #d1 cyl9d] l9k4 ,9 ! air drum l9k1 figs4 #dga & #dgb1 a capsule provides an air space ab\t ! c5t] ( ! l9k1 ! rate ( heat conduction ?r\gh ! conf9$ air be+ v sl[1 ! temp]ature ( t portion ( ! l9k rises rapidly ) increas+ curr5t1 r5d]+ ! bl[+ po9t practically con/ant2 fig4 #dgc %[s a section ?r\gh ! complete fuse4 ,9 ! flat l9k1 fig4 #dgd1 ! section is r$uc$ 9 ! c5t]1 cutt+ d[n z f> z possible ! volume ( metal to be fus$4 ,figs4 #dge to #dgh %[ v>i\s =m ( multiple l9k con/ruction4 ,by sub-divid+ ! metal1 increas$ radiat+ surface is obta9$ :i* p]mits a r$uction 9 ! volume ( fusible metal necess>y1 & ! metal vapor =m$ :5 ! fuse bl[s on heavy ov]load is m readily dissipat$4 ,figs4 #dgg & #dgh %[ two =ms ( ! cyl9d] l9k1 ! pla9 cyl9d] fig4 #dgg1 be+ us$ = l[ voltage & l>ge curr5t1 & fig4 #dgh1 = c]ta9 high t5sion s]vice4 ,! corrugat$ cyl9d] pres5ts m surface to ! fuse fill+ ?an ! pla9 type & secures a maximum radiat+ surface ) result+ m9imum volume ( metal = a giv5 curr5t4 ,ques4 ,h[ %\ld fuses be m\nt$8 ,ans4 ,!y %\ld be plac$ on a base ( slate1 porcela91 m>ble1 or o!r incombu/ible mat]ial4 ,ques4 ,:at is ! objection to copp] fuses8 ,ans4 ,!y heat p]ceptibly soon aft] _! rat$ capacity is pass$4 ,! melt+ temp]ature is high] ?an lead alloy4 ,ques4 ,^u :at consid]ation does ! *oice betwe5 swit*es & circuit break]s dep5d8 ,ans4 ,simple knife swit*es are suitable = use :5 ! circuit is n liable to be op5$ :ile c>ry+ l>ge curr5t4 ,a circuit break]1 op]at$ automatically or by h& %\ld be us$ = int]rupt+ heavy curr5ts4 ,illu/ration3 ,,figs4 #dgi & #dhj4--;,d ,w fuse indicator4 ,! op]ation is illu/rat$ 9 ! figures :i* %[ appe>ance ( ! label be=e ! bl[+ ( ! fuse1 fig4 #dgi1 & ! same fuse bl[n1 z indicat$ by ! appe>ance ( ! black spot )9 ! circle fig4 #dhj4 ,circuit ,break]s4--,a circuit break] is a swit* :i* is op5$ automatically :5 ! curr5t or ! pressure exce$s or falls bel[ a c]ta9 limit1 or :i* c be tripp$ by h&4 ,ques4 ,:at is ! con/ruction ( a circuit break]8 ,ans4 ,x is compos$ ( a swit* & a sol5oid 9 ! ma9 circuit4 ,:5 ! curr5t1 fl[+ ?r\gh ! circuit1 exce$s a c]ta9 value1 ! core ( ! sol5oid is drawn 9 & trips a trigg] :i* all[s ! swit* to fly op5 "u ! action ( a spr+4 ,illu/ration3 ,,figs4 #dha to #dhf4--,v>i\s op5 fuses4 ,fig4 #dha1 fuse = ma9 & bran* blocks2 fig4 #dhb1 /&>d railway fuse2 fig4 #dhc1 ,edison ma9 /yle2 fig4 #dhd1 ,w4,u4 patt]n2 fig4 #dhe1 ,bell telephone /yle2 fig4 #dhf1 sneak curr5t fuse4 ,:5 an op5 fuse bl[s z a result ( ov]load+1 ! rupture is accompani$ by a fla%1 & by spatt]+ ( ! fus$ mat]ial4 ,) l>ge curr5ts ?is ph5om5on is a s\rce ( dang]1 & ! use ( enclos$ fuses is accord+ly recomm5d$ :5ev] ! rat+ ( ! fuse exce$s #be amp]es4 ,v>i\s types ( enclos$ fuse are %[n 9 figs4 #dfh to #dgj4 ,!re are num]\s k9ds ( circuit break] to meet ! v>i$ conditions ( s]vice ( :i* may be m5tion$ ! foll[+3 #a4 ,maximum circuit break]2 #b4 ,m9imum circuit break]2 #c4 ,rev]se curr5t circuit break]2 #d4 ,maximum & rev]se circuit break]2 #e4 ,no voltage circuit break]4 ,illu/ration3 ,,figs4 #dhg & #dhh4--,rev]se curr5t circuit break]2 fig4 #dhh1 view look+ at end ( coils ( cut out1 %[+ direction ( curr5t4 ,a to bus b>2 ,b1 resi/ance lamp2 ,c1 bru% ( cut out2 ,d1 %unt coil2 ,e1 s]ies coil2 ,f1 core t trips cut out2 ,g1 to - bus b>2 ,h1 to pole ( dynamo4 ,( ^! ! maximum1 rev]se1 & maximum & rev]se types are ! m important4 ,a maximum circuit break] is equival5t to a fuse1 b has ! advantage t x c be at once reset1 :]eas a fuse mu/ be replac$4 ,a rev]se break] is us$ 9 connection ) dynamos 9 p>allel1 to automatically cut out a ma*9e if x take m ?an say1 #aj p] c5t4 motor curr5t4 ,maximum & rev]se circuit break]s are frequ5tly us$ on dynamo panels4 ,illu/ration3 ,,figs4 #dhi & #dij4--;,front & top views ( ,i-,t-,e automatic ov]load circuit break]4 ,9 fig4 #dhi ! curr5t 9 ! circuit ent]s at ,a1 passes ?r\gh ! sol5oid coil ,b 7:i* 9 its iron jacket becomes a p[]ful magnet71 ?r\gh ! copp] t]m9al ,c1 to ! contact blades ,d1 across ! bridge at ,e to ! contact blades ,f1 & out into ! l9e at ,g4 ,! pa? ( ! curr5t z indicat$ above is m cle>ly indicat$ 9 ! top view fig4 #dij4 ,:5 ! curr5t 9 ! sol5oid coil produces suffici5t magnetism to ov]come ! weight ( ! plung]1 ! latt] is drawn up ) con/antly increas+ velocity until x /rikes a re/ra9+ lat* or trigg] :i* =ces ! arm out ( ! swit*1 ?us automatically op5+ ! circuit4 ,! device is s con/ruct$ t 9 op5+ ! circuit ! arc is brok5 on ! c>bon contacts in/ead ( ! copp] contacts4 ,ques4 ,describe a rev]se curr5t circuit break] or discrim9at+ cut out4 ,ans4 ,?is type ( circuit break] is arrang$ to op5 a circuit 9 ! ev5t ( curr5t fl[+ 9 ! circuit 9 a direction rev]se to ! normal4 ,?is is sometimes effect$ by w9d+ ! electromagnet ( ! circuit break] ) two coils1 "o connect$ z a %unt across ! ma9 circuit & ! o!r 9 s]ies ) ! ma9 circuit1 ! two coils be+ s arrang$ t :5 ! ma9 curr5t fl[s 9 ! normal direction _! effects assi/ "o ano!r1 :]eas1 :5 ! ma9 curr5t rev]ses1 ! effects ( ! coils are neutraliz$ & ! break] op5s4 ,illu/ration3 ,,fig4 #dia4--,roll]-,smi? ,s4,e4 pla9 ov]load circuit break]4 ,9 op]ation1 curr5t ent]+ ?r\gh ! l[] /uds fl[s ?r\gh ! lam9at$ /rap w9d+s ,c1 f ?is into ! arm ,d1 ?r\gh ! contact plate ,e1 into ! /ation>y bru% ,f1 & f9ally out ?r\gh ! upp] /ud ,q4 ,9 its passage ?r\gh ! lam9at$ w9d+s ,c1 ! squ>e core ,a is ( c\rse magnetiz$ to a degree dep5d5t on ! curr5t /r5g?4 ,:5 ?is magnetization rea*es a pre-det]m9$ value1 ! attraction ex]t$ on ! ends ,k ( ! pivot$ armature causes ! same to rise ) great & increas+ velocity1 f9ally br++ ! f+] ,d :i* =ms "p ( ! armature into viol5t contact ) ! face ,r ( ! correspond+ projection on ! h\s+ :i* c>ries ! h&le & ! roll] ,h4 ,?is heavy bl[ causes ,h1 9 its rotation ab\t ! %aft ,j1 to g ov] ! c5t] & consequ5tly all[s ! /rong outw>d pressure ( ! bru% ,f & ! resili5t coil ,c to ?r[ ! arm outw>d ) a high velocity & s break ! circuit1 fir/ betwe5 ! bru% f+]s & ! contact plate & f9ally betwe5 ! c>bons ,s & ,f1 ! "o ( :i* is rigidly secur$ to ! arm & ! o!r ( :i* is resili5tly m\nt$ on its support+ spr+4 ,to reset ! break]1 ! h&le1 :i* ! act ( op5+ has rais$1 is pull$ d[n1 ?us br++ roll] ,h into engagem5t ) roll] ,g once m & 9 t way =c+ ! arm back into its initial position4 ,illu/ration3 ,,fig4 #dib4--,roll] ,smi? ,s4,e4 comb9ation ov]load & und]load circuit break]4 ,atta*$ to ! support+ frame ,b is ! ext5sion ,z1 :i* l ,b1 is ( non-magnetic mat]ial & c>ries a rectangul> magnetic core ar\nd :i* !re are wrapp$ lam9at$ copp] conductors4 ,h+$ at ,u is a heavy cup-%ap$ mass ( magnetic mat]ial1 & h+$ at ,v is a flat lev] ,x :i* be>s aga9/ ! ext5sion ,y secur$ to ! h\s+ :i* c>ries ! op]at+ h&le4 ,! circuit ?r\gh ! break] conveys ! curr5t ar\nd ! w9d+s ( ?is und]load coil c>ri$ by frame ,z & passes f x to ! regul> ov]load w9d+ ,c f :i* x pursues ! same c\rse & ex]cises ! same function z 9 a pla9 ov]load break]4 ,! core ( ,z be+ ?us magnetiz$1 ! cup-%ap$ memb] ,w is held 9 firm contact !re) & ! lev] ,x hangs free4 ,%\ld1 h[ev]1 ! curr5t fall bel[ ! m9imum value1 ,w is no long] su/a9$ by ! magnetic attraction b drops away1 sw++ on its h+e ,u until ! projection on ! heel !re( /rikes ! lev] ,x1 :i* bl[ is transmitt$ ?r\gh ,y to ! h&le & ?us trips ! break]4 ,:5 clos+ to reset ! break]1 ! h&le is manipulat$ j z 9 ! case ( a pla9 ov]load break]1 t is1 x is pull$ d[n1 ?us n only clos+ & lock+ ! break] z be=e b ?r\gh ! pressure ex]t$ by ,y on ,x & by ,x on ,w1 putt+ ! latt] into contact ) its rectangul> core to :i* x w adh]e if ! necess>y curr5t be pres5t4 ,ques4 ,/ate "s disadvantages ( a discrim9at+ cut out4 ,ans4 ,if "o curr5t rev]se v rapidly1 & soon rea* a l>ge value 9 ! opposite direction1 x is possible ! cut out may n op5 at ! desir$ in/ant1 & !reaft] ! effect ( ! heavy rev]se curr5t w be s great t ! break] w be held 9 m & m /rongly2 a second disadvantage is t %\ld ! supply fail1 ! break] w op5 9 any case1 & h to be reset be=e ! supply c be resum$1 ?\gh 9 c]ta9 cases1 z1 = in/ance :]e !re is a motor load1 ?is feature is an advantage & n a disadvantage1 s9ce ! break] acts z a no-voltage cut out z well z a rev]se curr5t cut out4 ,rev]se break]s1 h[ev]1 c be made positive 9 _! action2 t is1 !y c be s arrang$ t a rev]se curr5t ex]ts a positive pull on ! tripp+ ge>1 s t ! great] ! rev]se curr5t1 ! great] ! tripp+ effect4 ,ques4 ,:at are "t limit atta*m5ts8 ,ans4 ,devices :i* are fitt$ to circuit break]s & :i* act z damp]s & prev5t ! too sudd5 op]ation ( ! break]s on :at may be only a tempor>y ov]load or rev]se curr5t4 ,by hav+ diff]5t "t limits on fe$] & dynamo break]s x c be ensur$ t ! =m] op]ate be=e ! latt]1 & suitably 9 o!r cases :]e x is desir$ t "o break] %all op]ate be=e ano!r4 ,ques4 ,describe a "t limit atta*m5t4 ,ans4 ,!re are num]\s types4 ,x may consi/ ( a clockwork device1 a weight act+ on a small drum or pulley1 a modifi$ da% pot arrangem5t1 or a device op]at+ by ! expansion ( a conductor due to ! heat g5]at$ by a curr5t pass+ ?r\gh x4 ,ques4 ,h[ %\ld a "t limit device be arrang$8 ,ans4 ,x %\ld be s arrang$ t ! heavi] ! ov]load ! quick] ! device acts1 until ) a %ort circuit ! device is almo/ in/antane\s 9 its action4 ,illu/ration3 ,,fig4 #dic4--;,diagram %[+ connections ( a rheo/at4 ,! v>i\s resi/ance coils are connect$ to brass buttons or contacts4 ,! rheo/at is connect$ 9 s]ies 9 ! circuit t x is to control4 ,9 op]ation :5 ! lev] is on contact #a1 ! curr5t is oppos$ by all ! resi/ance ( ! rheo/at s t ! fl[ is v small4 ,z ! lev] is mov$ ov] contacts #a1 #b1 #c1 etc41 ! coils are successively cut out1 ?us dim9i%+ ! resi/ance1 & :5 contact #aa is rea*$ all ! resi/ance is %ort circuit$ all[+ ! full curr5t to fl[4 ,9 "s types ( rheo/at ! wire is w\nd ar\nd an iron frame-"w :i* has be5 previ\sly dipp$ into a firepro( insulat+ enamel4 ,! advantage ( ?is con/ruction is t ! heat f ! wire is dissipat$ mu* m rapidly1 s t a mu* small] wire c be us$ to c>ry a giv5 curr5t4 ,! size ( su* an enamel$ rheo/at requir$ = absorb+ a giv5 am\nt ( en]gy is mu* small] ?an "o made ( coils ( wire /ret*$ betwe5 an iron support+ framework4 ,rheo/ats4--,^! devices consi/ ( conductors ins]t$ into a circuit = ! purpose ( dim9i%+1 ei!r con/antly or 9 a v>iable degree1 ! am\nt ( curr5t fl[+1 or to develop heat by ! passage ( a curr5t ?r\gh !m4 ,rheo/ats design$ to be us$ 9 />t+ electric motors are frequ5tly call$ />t+ boxes4 ,ques4 ,describe ! con/ruction ( a rheo/at4 ,ans4 ,9 fig4 #dic1 resi/ance coils1 ,a1 ,b1 ,c1 etc41 are m\nt$ 9 a frame or box1 & are connect$ at int]vals to ! contacts #a1 #b1 #c1 etc4 ,! rheo/at arm or lev] ,l is pivot$ at ,s1 & :5 mov$ ov] ! contacts1 ins]ts m or less ( ! resi/ance 9 ! circuit ?us regulat+ ! fl[ ( ! curr5t4 ,"o t]m9al ,m ( ! rheo/at is connect$ to ! fir/ contact & ! o!r t]m9al ,o1 to ! lev] at ,s4 ,illu/ration3 ,,fig4 #did4--,/>t] ) no voltage release = a s]ies motor4 ,a helical spr+ coil$ ar\nd ! lev] pivot ,p1 & act+ on ! lev] ,a1 t5ds to keep x 9 ! (f position aga9/ ! /op ,s4 ,?is lev] c>ries a s(t iron armature ,i1 :i* is held by ! poles ( ! electromagnet ,e1 :51 9 />t+ ! motor1 ! arm has be5 gradually =c$ ov] z f> z x w g4 ,%\ld any?+ happ5 to int]rupt ! curr5t :ile ! motor ,m is runn+1 ,e w lose its magnetism & ,a w be releas$1 & w fly ov] to ! (f position4 ,e is usually %unt$ by a small resi/ance ,r1 s t only a portion ( ! ma9 curr5t fl[s ?r\gh x4 ,?is device con/itutes ! no voltage release1 & ensures t all ! resi/ance is 9 circuit e "t ! motor is />t$4 ,ques4 ,h[ is a />t+ box connect$ to a motor8 ,ans4 ,9 s]ies4 ,ques4 ,:y %\ld a />t+ box be us$ ) a motor8 ,ans4 ,if ! l9e voltage %\ld be appli$ directly to ! t]m9als ( ! armature :5 n runn+1 an excessive fl[ ( curr5t w result1 on acc\nt ( ! l[ resi/ance4 ,accord+ly1 to prev5t injury to ! w9d+1 a v>iable resi/ance or />t+ box is ins]t$ betwe5 "o supply t]m9al & ! armature s t ! pressure may be appli$ gradually :ile ! motor is com+ up to spe$4 ,illu/ration3 ,,fig4 #die4--,/>t] ) no voltage release = a %unt motor4 ,! t]m9als ( ! motor are at ,m1 ,m'1 m1 & ^? ( ! />t] at ,s1 ,s'1 s4 ,! lev] ,,sa is %[n 9 ! on position4 ,! curr5t ent]s ! motor at ! t]m9al ,m1 & !re divides1 "p go+ ?r\gh ! field coil ,f1 & ! ma9 curr5t ?r\gh ! motor armature ,a4 ,! armature curr5t ent]s ! />t] at ! t]m9al ,s'1 & trav]s+ ! lev] ,,sa1 leaves by ! t]m9al ,s4 ,! field curr5t ent]s ! />t] at ! t]m9al s1 trav]ses ! coil ( ! magnet ,e 7:i* holds up ! armature a l9k$ to ! lev]7 & !nce completes its j\rney ?r\gh ! :ole ( ! resi/ance ,r1 & ?r\gh ! lev] ,,sa1 to ! t]m9al ,s4 ,:5 ! supply is cut (f by op5+ ,,sw1 or %\ld ! field circuit be accid5tally brok51 ! magnet ,e w release a & ! lev]1 :i* w !reupon fly to ! (f /op ,o4 ,x %\ld be notic$ t :5 ,,sa is (f1 ,a & ,f =m a clos$ circuit ) ! resi/ance ,r & magnet ,e4 ,! inductance ( ,f has consequ5tly no *ance ( caus+ de/ructive sp>k+ :5 ! curr5t is %ut (f4 ,9 />t+ ! motor1 ,,sw is fir/ clos$1 & !n1 z ! lev] is sl[ly mov$1 ! resi/ance ,r1 :i* at fir/ is all 9 circuit ) ,a1 is gradually transf]r$ f ,a to ,f4 ,! resi/ance ( ,r is too small to affect appreciably ! curr5t 9 ,f1 :i* necess>ily consi/s ( a comp>atively l>ge numb] ( turns ( f9e wire4 ,! arrangem5t is adopt$ to r5d] ! break+ ( ! %unt circuit unnecess>y & is r5d]$ cle>] by ! diagram fig4 #dif4 ,x %\ld be not$ t ,e may be provid$ ) a %ort circuit+ key or pu% if requir$4 ,illu/ration3 ,,fig4 #dif4--,simplifi$ diagram ( ! connections ( fig4 #die4 ,illu/ration3 ,,fig4 #dig4--,/>t] ) no voltage release & ov]load release connect$ to a comp\nd motor4 ,) a %unt motor1 ! only diff]5ce 9 ! diagram w\ld be t ! s]ies w9d+ ,,se w\ld be abs5t1 & ! armature ,a w\ld !n be connect$ /raight across betwe5 ! ma9 t]m9als ,m & ,m'4 ,:5 swit* ,,sw is clos$1 ! curr5t w ent] ! />t] at its t]m9al ,s1 & pass ?r\gh ! magnet coil m' ( ! ov]load release to ! swit* lev] ,l1 :i* is %[n 9 ! (f position4 ,z soon z ,l is mov$ up to make contact ) ! fir/ contact ,s ! curr5t divides2 "p go+ ?r\gh ! resi/ance ,r & ! t]m9als ,s' & ,m' to ! s]ies coil ,,se 7if a comp\nd motor7 & armature ,a2 & "p ?r\gh ! no voltage magnet ,e to ! %unt w9d+ ,,%4 ,z ! lev] ,l is mov$ up t[>d ,e1 ! effect is to take ,r out ( ! armature circuit & put x into ! %unt circuit4 ,:5 ! iron armature a1 fix$ on ! swit* lev]1 comes aga9/ ! poles ( ,e1 ! lam9at$ copp] bru% ,c be>s aga9/ ! blocks ,b1 ,b1 & s af=ds a bett] pa? = ! curr5t ?an ?r\gh ! sp9dle s4 ,%\ld ! supply voltage fail1 ei!r tempor>ily or p]man5tly1 ,e w release a1 & ,l w fly (f "u ! t5sion ( a helical spr+ coil$ r\nd s4 ,if !re %\ld be an ov]load on ! motor1 t5d+ to pull x up & cause an excess ( curr5t to fl[ ?r\gh ! armature2 ?is excess curr5t1 pass+ ?r\gh m'1 w make x attract its armature1 s br++ two contacts toge!r at ,k :i* w %ort circuit ,e1 & all[ ! swit* to fly (f4 ,! connections betwe5 ,e & m' are n %[n 9 ! figure1 b !y are indicat$ at ,c 9 fig4 #dih1 :i* is a simplification ( fig4 #dig1 & :i* %\ld be c>efully comp>$ !re)4 ,:5 only ! normal curr5t is fl[+1 ! attraction betwe5 m' & its armature is n suffici5t to pull ! latt] up4 ,! actual =ms & arrangem5t ( p>ts on ! />t]s are well %[n 9 "s ( ! figures4 ,ques4 ,:at atta*m5ts %\ld be provid$ on a />t+ box8 ,ans4 ,an ov]load release1 & a no voltage release4 ,ques4 ,describe ^! devices4 ,ans4 ,! ov]load release is an electromagnetic circuit break] t op5s ! circuit if ! motor become greatly ov]load$4 ,a no voltage release may consi/ ( an electromagnet 9 s]ies ) ! %unt field circuit2 x holds ! rheo/at arm 9 ! op]at+ position z long z curr5t fl[s ?r\gh ! %unt field f ! l9e4 ,if ! l9e swit* be op5$ or ! %unt field circuit accid5tally brok51 ! device becomes demagnetiz$ & releases ! arm1 :i* returns to its />t+ position by ! action ( a spr+4 ,illu/ration3 ,,fig4 #dih4--,simplifi$ diagram ( ! connections ( />t] connect$ to comp\nd motor z %[n 9 fig4 #dig4 ,! g5]al arrangem5t ( swit*es1 cut outs & />t+ boxes %\ld be 9 accordance ) ! requirem5ts ( ! ,national ,electrical ,code z foll[s3 ,ea* motor & />t+ box mu/ be protect$ by a cut out & controll$ by a swit*1 said swit* pla9ly indicat+ :e!r 'on' or '(f4' ,! swit* & rheo/at mu/ be locat$ )9 sight ( ! motor1 except 9 cases :]e special p]mission to locate !m else:]e is giv51 9 writ+ by ! inspection dep>tm5t hav+ jurisdiction4 ,:]e ! circuit break+ device on ! motor />t+ rheo/at discs disconnects all wires ( ! circuit1 ?is swit* may be omitt$4 ,ov]load release devices on motor />t+ rheo/ats w n be consid]$ to take ! place ( ! cut out requir$ if !y be inop]ative dur+ ! />t+ ( ! motor4 ,! swit* is necess>y = entirely disconnect+ ! motor :5 n 9 use1 & ! cut out to protect ! motor f excessive curr5ts1 or c>eless h&l+ :5 />t+4 ,an automatic circuit break] disconnect+ all wires ( ! circuit1 may1 h[ev]1 s]ve z bo? swit* & cut out4 ,illu/ration3 ,,fig4 #dii4--,view %[+ g5]al arrangem5t ( a swit*bo>d4 ,! wires are %[n to illu/rate ! v>i\s connections1 b 9 actual con/ruction ^! wires are connect$ on ! back ( ! swit*bo>d4 ,swit*bo>ds4--,a swit*bo>d consi/s ( a panel or s]ies ( panels ( slate1 m>ble1 soap/one or brick tile erect$ 9 an electric plant = ! purpose ( m\nt+ 9 a conv5i5t gr\p ! in/rum5ts = controll+ & di/ribut+ ! curr5t & safegu>d+ ! sy/em4 ,swit*bo>ds may be divid$ accord+ to op]ation into two classes3 #a4 ,direct control2 #b4 ,remote control4 ,a direct control swit*bo>d has all its app>atus m\nt$ directly on ! bo>d & controll$ by h&1 :ile 9 ! remote control type1 ! ma9 curr5t c>ry+ p>ts are at "s di/ance f ! op]at+ bo>d1 ! control be+ effect$ by me*anical devices or by electric motors or sol5oids4 ,:5 ! control sy/em ( a plant is v ext5sive1 x sometimes occupies a sep>ate build+ kn[n z ! swit* h\se4 ,ques4 ,:at may be said ) respect to ! mat]ial = swit*bo>ds8 ,ans4 ,9 ord] to avoid dang] ( fire f %ort circuits1 ! panel %\ld be made ( "s non-combu/ible mat]ial1 su* z m>ble1 slate1 glass plates or e>!nw>e tiles4 ,if slate be us$1 c>e %\ld be tak5 to h x free f conduct+ ve9s1 or x %\ld be m>bleiz$1 t is1 subject$ to a treatm5t t w fill up ! pores ( ! ve9s & ?us prev5t ! absorption ( moi/ure4 ,wood is seldom us$1 except 9 cases :]e ! swit*es1 fuse blocks1 wire supports1 etc41 are all m\nt$ on porcela9 or o!r incombu/ible mat]ial4 ,ques4 ,h[ %\ld ! in/rum5ts & connections be arrang$ on a swit*bo>d8 ,ans4 ,!y %\ld be arrang$ s z to provide ! %orte/ possible pa? = ! curr5t1 & pref]ably always 9 ! same direction1 t is1 f "r to left or f top to bottom1 ! connect+ wires be+ br\ght 9 on "o side & out on ! o!r1 & ! cross+ ( wires avoid$ z f> z possible4 ,all wires & curr5t c>ry+ p>ts %\ld be kept f> en\gh ap>t at all po9ts to prev5t accid5tal contact or ! jump+ across ( ! curr5t :]e !re is a great diff]5ce ( voltage4 ,su* wires %\ld be also kept at a suffici5t di/ance f screw heads1 metal brackets1 gas pipes1 wat] pipes1 & o!r conduct+ bodies1 9 ord] to prev5t accid5tal gr\nds or %ort circuits4 ,all in/rum5ts & swit*es %\ld be plac$ s z to be conv5i5tly accessible = obs]vation & op]ation1 & suffici5tly out ( rea* ( accid5tal contact by p]sons2 o!rwise !y %\ld be protect$ by "s =m ( insulat+ %ield4 ,illu/ration3 ,,fig4 #ejj4--,small swit*bo>d suitable = two dynamos2 view %[+ ammet]s & voltmet]s1 swit*es1 circuit break]s1 etc4 ,ques4 ,:at type ( swit* is us$ on swit*bo>ds8 ,ans4 ,! knife swit*4 ,ques4 ,describe a small swit*bo>d4 ,ans4 ,fig4 #ejj %[s "o suitable = two dynamos4 ,at ! top is a voltmet] & two ammet]s4 ,imm$iately bel[ is a r[ ( fe$] swit*es s]v+ to connect & disconnect ! v>i\s fe$]s ) & f ! bus b>s :i* are m\nt$ beh9d ! bo>d4 ,bel[ are two rheo/at h&:eels1 & two l>ge swit*es connect+ ! dynamos ) ! bus b>s4 ,,vs is a voltmet] swit* connect+ ! voltmet] ) v>i\s p>ts ( ! sy/em4 ,bel[ ! voltmet] swit* is a d\ble ?r[ swit* to transf] ! bus b>s f connection ) ! dynamo swit*es to "o ) "s o!r s\rce ( curr5t su* z a /reet circuit1 9 ! ev5t ( a breakd[n4 ,at ! bottom are two circuit break]s4 ,illu/ration3 ,,fig4 #eja4--;,diagram %[+ v>i\s connections ( voltmet] swit* ( ! small swit*bo>d %[n 9 fig4 #ejj4 ,ques4 ,describe ! voltmet] swit*4 ,ans4 ,fig4 #eja %[s ! connections1 f :i* x c be se5 t ! voltmet] c be connect$ ) ! t]m9als ( ei!r dynamo or ) ! bus b>s1 or ) ei!r a c5tral or remote "p 9 ! lamp circuits4 ,"u ord9>y conditions x rema9s connect$ to ! circuit at ! c5tral po9t ( di/ribution4 ,:5 "o dynamo is already 9 circuit1 h[ev]1 & x becomes necess>y to connect up ! o!r "o1 ! voltage ( ! latt] mu/ be ! same z t at ! bus b>s4 ,accord+ly1 connections are provid$ to ! voltmet] swit* su* t ! att5dant c comp>e ! voltages at ! dynamo t]m9als & bus b>s be=e clos+ ! dynamo swit*4 ,all ! positive connections are on "o side ( ! circle swept by ! swit* & all ! negative connections on ! o!r side4 ,illu/ration3 ,,fig4 #ejb4--,roll]-,smi?1 s+le pole1 pla9 ov]load circuit break]4 ,z its "n indicates1 ! function ( ! pla9 ov]load circuit break] is to automatically int]rupt ! circuit 9 :i* x is plac$ :5 ! fl[ ( curr5t ?r\gh x exce$s ! pr$et]m9$ limit = :i* ! app>atus is set4 ,x is ! mo/ common ( all ( ! types & is utiliz$ = ! protection ( dynamos & motors & all o!r electrical app>atus :i*1 by reason ( ! conditions ( op]ation1 may become subject to loads 9 excess ( ! normal4 ,! s+le pole type may be us$ sep>ately = ! protection ( a s+le wire ( a giv5 circuit or gr\p$ to protect ! two or m wires ( "o circuit1 becom+ 9 ! latt] case ! s call$ indep5d5t arm multipole app>atus4 ,! action ( ?is type ( circuit break] is fully expla9$ 9 fig4 #dia4 ,,hawk9s ,,practical ,,libr>y ,,( ,,electricity ,,9 ,,h&y ,,pocket ,,=m ,,price #a ,,ea* ,!y are n only ! be/1 b ! *eape/ "w publi%$ on ,electricity4 ,ea* numb] be+ complete 9 itself4 ,sep>ate numb]s s5t po/paid to any address on receipt ( price4 ,!y are gu>ante$ 9 e way or y\r money w be return$4 ,complete catalog ( s]ies w be mail$ free on reque/4 ,,electrical ,,guide1 ,,no4 #a ,conta9+ ! pr9ciples ( ,elem5t>y ,electricity1 ,magnetism1 ,induction1 ,exp]im5ts1 ,dynamos1 ,electric ,ma*9]y4 ,,electrical ,,guide1 ,,no4 #b ,! con/ruction ( ,dynamos1 ,motors1 ,armatures1 ,armature ,w9d+s1 ,in/all+ ( ,dynamos4 ,,electrical ,,guide1 ,,no4 #c ,electrical ,in/rum5ts1 ,te/+1 ,practical ,managem5t ( ,dynamos & ,motors4 ,,electrical ,,guide1 ,,no4 #d ,di/ribution ,sy/ems1 ,wir+1 ,wir+ ,diagrams1 ,sign ,fla%]s1 ,/orage ,batt]ies4 ,,electrical ,,guide1 ,,no4 #e ,pr9ciples ( ,alt]nat+ ,curr5ts & ,alt]nators4 ,,electrical ,,guide1 ,,no4 #f ,alt]nat+ ,curr5t ,motors1 ,trans=m]s1 ,conv]t]s1 ,rectifi]s4 ,,electrical ,,guide1 ,,no4 #g ,alt]nat+ ,curr5t ,sy/ems1 ,circuit ,break]s1 ,measur+ ,in/rum5ts4 ,,electrical ,,guide1 ,,no4 #h ,alt]nat+ ,curr5t ,swit* ,bo>ds1 ,wir+1 ,p[] ,/ations1 ,in/allation & ,op]ation4 ,,electrical ,,guide1 ,,no4 #i ,telephone1 ,telegraph1 ,wireless1 ,bells1 ,light+1 ,railways4 ,,electrical ,,guide1 ,,no4 #aj ,mod]n ,practical ,applications ( ,electricity & ,ready ,ref]5ce ,index ( ! #aj ,numb]s4 ,!o4 ,audel ,co41 ,publi%]s4 #gb ,,fif? ,,av5ue1 ,,new ,,york ,transcrib]'s ,note3 ,inconsi/5t spell+ & hyph5ation are z 9 ! orig9al4