1. Calculate the voltage induced in the armature winding of a 4-pole, lap-wound, dc machine having 728 acve conductors and running at 1800 rpm. he !u" per pole is #0m$%. &. '((.2 ) C. 720.4 ) *. 4'8.2 ) +. 2#'.4 ) 2. & 4-pole wave-wound armature has 144 slots with two coil sides per slot, each coil having two turns. f the !u" per pole is 20m$% and the armature rotates at 720rpm. $hat is the induced voltage &. 1#8.24 ) C. '.12 ) *. #4.' ) +. 24'.78 ) #. & dc machine has 4-pole, wave-wound armature with 4' slots and 1' conductors per slot. f the induced voltage in the armature is 480 ) at 1200rpm, determine the !u" per pole. &. 48 m$% C. 0.4 m$% *. 1.2 m$% +. 1'.# m$% 4. & motor is suppl/ing 70 -m to a load. f the sha of the motor rotates at 1(00rpm, determine the power developed at the motor. &. 10,'' $ C. 11,#7 $ *. 8,20' $ +. ',78 $ (. & '-pole, lap-wound armature, having 720 conductors, rotates in eld of 20.#( m$%. f the armaturer current is 78 &, what is the armature tor3ue developed &. 18.1 -m C. 181. -m *. 1.18 -m +. 11.8 -m '. & 2#0-) shunt motor delivers #0 hp at the sha at 1120 rpm. f the motor has an ecienc/ of 875 at this load, determine calculate the developed tor3ue. f the tor3ue loss due to fricon and windage is 75 of the sha tor3ue. &. 204.2 -m C. 10.8 -m *. 1'8.4 -m +. 224.4 -m 7. & motor has a nameplate rang of 1( hp 6 11'0 rpm. olve for the rated tor3ue. &. 10#.' l%- C. 121.4 l%- *. '7.8 l%- +. 12#.# l%- 8. Calculate the ecienc/ of a 2#0 )olt shunt motor from the following data nput current is 1.8 &mp, %alance reading is 14 l%s, tare weight is 2 l%s, %ra9e arm is 2 long 6 peed is 1100 rpm. &. 82.4 5 C. 82.4 5 *. 81.4 5 +. 8'.( 5 . & 2#0-volt shunt motor has an armature resistance of 0.28 ohm and a led resistance of 11( ohms. &t no-load, the line current is 8 amperes and the speed is 2#00 rpm. $hat is the speed when the line current is (2 amperes &ssume %rush drops of 1 volt at no-load and # volts at load condion and constant !u" densit/. &. 21(4 rpm C. 2178 rpm *. 2212 rpm +. 21(( rpm
10. & 120 volt dc shunt motor having an armature circuit resistance of 0.2 ohm and eld circuit resistance of '0 ohms draws a line current of 40 at full load. he %rush drop is #-volts and rated speed is 1800 rpm. $hat is the speed at half load &. 00 rpm C. #'00 rpm *. 18'# rpm +. 720 rpm 11. he no-load armature current of a 220 volts shunt motor is # amperes. he no load speed is (0 rpm and the total resistance of the armature circuit :a including the %rushes is 0.2 ohm. f the motor is loaded, the !u" is reduced %/ 1(5 and the resistance of 2 ohms is inserted in the armature, the speed is then '0 rpm, what is the electromagnec tor3ue in l%- &. '# C. (( *. (8 +. '0 12. he power input to a #0 ;p 220-volt shunt motor is 2100 wa &. 1#' $a
18. & 100 )olt dc series motors run at 400 rpm when ta9ing a current of (( &mp. &rmature resistance is 0.0# ohm, eld resistance is 0.00# ohm. f the load tor3ue remains the same, what is the input current when the eld is shunted %/ a resistor of 0.02 ohm &. '2 & C. 7' & *. 87 & +. 82 &
1. & 10 hp, 2#0 )olt, 1000 rpm series motor having rated ecienc/ of 8(.(5, armature resistance of 0.1( ohm. $hat value of starng resistance so that the starng tor3ue is e3ual to 1(05 of the rated-load tor3ue &. 4.(? C. (.4? *. 4.(2? +. 4.'7? 20. & 4 pole, 12 slot lap wound armature has two coil side per slot. &ssuming single turn coils and progressive winding, what is the %ac9 pitch &. # C. ' *. ( +. 7 21. n a 12 pole, triple" lap wound dc armature, each conductor can carr/ 100 &. $hat is the rated current of this armature &. '00 & C. #'00 & *. 1200 & +. 2400 & 22. & 400 )olt, 1000 &mp, simple" lap-wound dc generator has 10 poles, 8'0 conductors. +etermine the num%er of &mp-turns in the pole face to give full compensaon if the pole face covers 705 of pole span. &. #,010 & C. 1,(0( & *. ',200 & +. #,'8 & 2#. & generator armature with 1000 t urns rotates at '0 revoluons per second across a pair of pole with a !u" densit/ of 0.2 esla. esla. he pole face has an area of 0.1 s3. m. @ind the induced emf. emf. &. #.7 9) C. 7.( 9) *. 2.4 9) +. .# 9) 24. & 10-9$, 10-9$, 2(0-) shunt generator, generator, having an armature resistance of 0.1? and a eld resistance of 2(0?, delivers full-load at rated voltage and 800 rpm. he machine is now run as a motor while ta9ing 10 9$ at 2(0 ). $hat is the speed of the motor eglect %rush contact drop. &. 774.8 rpm C. 814.' rpm *. 804.' rpm +. 784.' rpm 2(. & self-e"cited shunt generator supplies supplies a load of 12.( 9$ at 12( ). ). he eld resistance is 2(? and the armature resistance is 0.1?. he total voltage drop %ecause of %rush contact and armature reacon at this load is #.( ). Calculate the induced armature voltage. &. 12 ) C. 1#( ) *. 2'# ) +. 1# )
2'. & 420 9$ '00-)olt, (80 rpm long shunt generator has an armature resistance of 0.0# ohm, series eld resistance of 0.01 ohm, shunt eld resistance of 4( ohms and => of 12 9$. Calculate Calculate the necessar/ driving tor3ue at rated load in l%-. &. ((80 C. (8#0 *. (280 +. (4'0 27. & (0 9$, 9$, (00 )olt short shunt generator has an armature resistance, series eld resistance and shunt eld resistances are 0.0(?, 0.0'? and 2(# ? respecvel/. respecvel/. $hat is the armature power generated &. (1.7' 9$ C. (2.1# 9$ *. 48.74 9$ +. (1.(2 9$ 28. &ssuming a constant constant eld e"citaon, calculate calculate the no-load voltage of a separatel/ e"cited e"cited generator the armature voltage is 1(0 volts at 1800 rpm. $hat is the voltage if the speed is increased to 2000 rpm &. 1'7 C. 1## *. 120 +. 180 2. & separatel/-e"cited separatel/-e"cited dc generator has the following following data armature resistance, resistance, 0.04?A eld resistance, 100?A total core and mechanical losses, '0 $A voltage across the eld, 2#0 ). he generator supplies a load at a terminal voltage of 2#0 ). Calculate the ma"imum value of the generator ecienc/. ecienc/. &. #.85 C. #.25 *. 2.75 +. 8.25 #0. wo shunt generators A 6 B operates in parallel and their load characteriscs ma/ %e ta9en as straight line. he voltage of generator A falls from 240 )olts at no-load to 220 )olts at 200 &mp while that of B falls from 24( )olts at no-load to 220 )olts at 1(0 &mp. +etermine the common terminal voltage when the load is '7 9$. &. 22# )olts C. 241 )olts *. #22 )olts +. #1( )olts
DC machines Supplementary Problems 1. +irt on the motor commutator ma/ produce BBBBBBBBBBBBB BBBBBBBBBBBBB &. isolaon C. lower tor3ue *. e"cessive spar9ing +. power loss 2. f a motor frame is found e"cessivel/ hot, which of the following is the >& li9el/ cause &. ver/ ver/ high high am%i am%ien entt temp temper erat atur ure e C. inad inade3 e3ua uate te inte intern rnal al ven venla lao on n *. fault/ starter +. e"cessive loading #. he simplest form of motor controller isDD. &. drum switch *. rela/
C. magnec switch +. toggle switch
4. :apid stopping of motor %/ momentaril/ reversing its connecons to the suppl/ is
&. Eogging *. plugging
C. inching +. se3uence operaon
(. & dc generator ma/ lose its residual magnesm %ecause ofDD. &. var/ing loads C. over-e"citaon *. vi%raons +. heang or overload '. he simplest wa/ to shi load from one dc shunt generator running in parallel with another is to DD &. adEust their eld rheos eostat C. insert res resiistance in their eir ar armature cir circuits *. adEust adEust speed of their their prime movers movers +. use e3ual e3ualiFer iFer connecons connecons 7. @or %oth lap and wave windings. here are as man/ commutator %ars as the num%er of &. poles C. armature conductors *. slots +. winding elements 8. t is a +C motor that tends to over-speed when the eld opened while running &. shunt motor C. split phase motor *. series motor +. over-compounded motor . n +c shunt motors, how is the shunt eld connected in relaon with the armature winding &. parallel C. parallel series *. series-parallel +. series 10. +C shunt motors are commonl/ used in what applicaon &. high starng tor3ue C. constant speed *. low no-load speed +. high speed 11. $hich motor is used to start heav/ loads &. shunt *. cumulavel/ compound
C. series +. shaded pole
12. $hen the load is removed, which motor will run at the highest speed &. series C. shunt *. cumulavel/ compound +. diGerenall/ compound 1#. $hich motor is suita%le for elevator &. series *. cumulavel/ compound
C. shunt +. diGerenall/ compound
14. f a self-e"cited self-e"cited dc generator aer %eing installed fails to %uild up on its rst trial run, the rst thing to do is to. &. increa creasse the eld resi esistance C. rever eversse eld eld conneco cons *. chec9 armature armature insulaon insulaon resistance resistance +. increase increase the speed of prime mover mover 1(. he voltage regulaon of over-compound over-compound generator alwa/s &. posive C. Hero *. negave +. high
1'. Calculate the current ta9en %/ a (00 )olt dc motor at ecienc/ 805, driving a pump at ecienc/ 705 which delivers 1400m# per minute at an eGecve head of 1( cm &. 2#1 & C. 12# & *. 21# & +. #12 & 17. & 240 )olts dc shunt motor has an armature current of (0 ampere, armature resistance of 0.2( running at 1200 rpm. f it is run at 220 )olts, what value of armature current when driving the same load. he eld is adEusted so that the speed remains at 1200 rpm. &. (( C. '0 *. (0 +. (7.( 18. & dc shunt motor develops 1( hp at 120 )olts. he armature resistance resistance is 0.0'1?. $hat is the armature current &. (.81 &mperes C. '.1( &mperes *. 1.8( &mperes +. 8.1( &mperes 1. & dc shunt motor develops 1( hp at 120 ). he armature ecienc/ is (5. $hat is the %ac9 e mf &. 114 )olts C. 118 )olts *. 122 )olts +. 117 )olts 20. & 120 )olts, 7( hp shunt motor has an armature resistance of 0.08? and eld resistance of '0?. $hat current is drawn when its %ac9 emf is 114.8 )olts &. '( & C. '# & *. '7 & +. 70 & 21. & 440 volt 7( hp shunt motor has an armature resistance of 0.18( ohm and eld resistance of #(0 ohms. he current drawn at full load is 1#( amperes. $hat is the %ac9 emf in volts &. 41(.# C. #4.8 *. #8.# +. 417.1 22. & 4 poles lap wound, dc machine has 728 acve conductors running at 1800 rpm. he !u" per pole is #0m$%, he armature current is 120 &, $hat is the electromagnec power developed in the armature in 9w &. 72.4 C. '(.( *. 78.' +. '2.4 2#. he armature and eld circuits circuits of a 2#0 volt shunt motor motor have resistance resistance of 0.#1 and 11( ohms respecvel/. respecvel/. t ta9es (2 &mp when operang at certain load. $hat is the armature power developed &. 14.4 hp C. 7.( hp *. 24.' hp +. 12.4 hp 24. & (00 volt shunt motor running at 720 rpm ta9es an armature current of (0 amp, its eGecve resistance 0.40 ohm. $hen a resistance of 1.' ohm is placed in series with the armature, what is the new speed &ssume that load or3ue is constant. &. 720 rpm C. 7(0 rpm *. '00 rpm +. '80 rpm
2(. & dc shunt motor runs at 00 rpm from a 4'0) suppl/ when ta9ing an armature current of 2( &. Calculate the speed at which it will run from a 2#0) suppl/ when ta9ing an armature current of 1(&. he resistance of the armature circuit is 0.8 ohm. &ssume !u" per pole at 2#0) have to decrease to7(5 of its value at 4'0) &. 4( C. (8( *. 48( +. (( 2'. & 2#0) shunt motor has an armature resistance of 0.28 ohm and a eld resistanceof 11( ohms, &t no-load, the line current is 8 amperes and the speed is 2#00 rpm. $hat is the speed when the line current is (2 ampere &ssume %rush drops of 1 volt at no-load and # volts at load condion and constant !u" densit/. &. 21(4 rpm C. 2178 rpm *. 2212 rpm +. 21(( rpm 27. he no-load armature current of a 220 volts shunt motor is # amperes. he no-load speed is (0 rpm and the total resistance of the armature circuit :a including the %rushes is 0.2 ohms is inserted in the armature, the speed is then '0 rpm, what is the electromagnec tor3ue in l%- &. '# C. (( *. (8 +. '0 28. & '-pole , lap-wound armature, having 720 conductors, rotates rotates in eld of 20.#( m$%. f the armature current is 78&, $hat is the tor3ue developed %/ the armature &. 18.1 -m C. 181. -m *. 1.18 -m +. 11.8 -m 2. he armature of dc machine running at 1200 rpm carries 4( & in current. f the included armature voltage is 1#0), 1#0), $hat is the tor3ue developed %/ the armature &. 4'.( -m C. 4(.' -m *. 4.'( -m +. 4(' -m #0. & motor has a nameplate rang of 1( hp and 11'0 rpm. olved for the rated tor3ue &. 10#.' l%- C. 121.4 l%- *. '7.8 l%- +. 12#.# l%- #1. he armature of dc motor has '48 conductors, '(5 of which are directl/ under the pole where the !u" densit/ is 48,000 lines per s3uare inch. f the core core diameter is 7 inches and its length length is 4 inches and the current in each conductor is 20 &mp. $hat is the tor3ue e"erted in the armature in l%- &. 41.8 C. 120.4 *. 14# +. 1##.4 #2. he armature of a motor has of 400 acve conductors, conductors, the !u" densit/ in eld %eing #000 gauss. he a"ial length of the armature is 20.#2 cm. he current is #0 amperes. +etermine the total force e"erted in the armature. &. 7#1.( C. 0.07 * '4(. +. 4#.2
##. & dc motor ta9es an armature current of 10( &mp at480 volts when running at 720 rpm. he resistance of the armature circuit is 0.2 ohm and eld resistance is ' ohms. $hat is the tor3ue developed in the armature &. ''8 -m C. 7(2 -m *. '10 -m +. '# -m #4. &n electric motor developeds 20 metr ic ;= at a speed of '00 rpm. $hat is the tor3ue &. 240 -m C. 210 -m *. 20 -m +. 2'0 -m #(. & dc shunt motor develops 7.8 hp at 120 volt, the armature ecienc/ is #5. $hat is the armature eGecve resistance &. 0.1 ohm C. 0.1' ohm *. 0.0' ohm +. 0.0( ohm #'. & Certain shunt motor has an armature resistance of 0.0(, t draws (0 amperes at a terminal voltage of 120 volts. &ssume other miscellaneous losses of 15. +etermine the output horsepower of the motor. motor. &. 8.( hp C. '.8 hp *. 7.1 hp +. 7.8 hp #7. Calculate the ecienc/ of a 2#0 )olt shunt motor from the following data. nput current is 1.8 &mp *alance reading is 14 l%s, tare weight is 2 l%s., %ra9e arm is 2 long 6 speed is 1100 rpm. &. 82.45 C. 84.25 *. 81.45 +. 8'.(5 #8. & 240 volt dc motor on %ra9e test too9 (2 &mp when running at 1(00 rpm. he spring %alance at the end of the 7' cm %ra9e arm reads #.( . $hat is the ecienc/ of the motor at this load &. 0.8( C. 0.0 *. 0.( +.0.8' #. he sha power of a shunt motor is 7.8 hp. ts armature draws (0 &mpere from 120 volts. he eld winding draws 1.2 &mp. $hat is the ecienc/ of the motor I*= Jct. 18K &. 4.75 C. '.(5 *. #5 +.8.25 40. & 1( hp 220 volt, 1200 rpm shunt motor ta9es ta9es (0 &mp. ts armature resistance is 0.1 ohm and eld resistance is 220 ohms. *rush contact voltage drop is 2 volts. @ricon and windage loss is 400 wa
due to %rush contact, #7 $A stra/-loss load, #7 $. he armature and the eld circuit resistance are 0.2( L and 2#0 L, respecvel/. respecvel/. Calculate the motor ecienc/ &. 8.('5 C. 87.85 *. 88.'5 +. 2.485 4#. &440 volt shunt motor has an armature resistance of 0.8 ohm and eld resistance of 200 ohms. $hat is the armature power developed when giving an output of 7.4'9$ at 8(5 ecienc/ &. 7.(' 9$ C. 7.4' 9$ *. 8.4' 9$ +. 7.2# 9$ 44. in a (hp, 2#0 volt, 1(00 rpm shunt motor, motor, the resistance of the armature including %rushes is 0.17( ohm and that of the shunt eld is '10 ohms. he stra/ power losses when the motor delivers rated load at rated voltage is #0( wa
*. 87 &
+. 82 &
(1. f the armature of an eight-pole dc machine were wound with a simple" wave winding, ;ow man/ =arallel paths would there %e &. 1' paths C. 8 paths *. 2 paths +. 4 paths (2. n a 4 pole, #( slot dc armature, calculate calculate the coil span &. 8 slots C. 10 slots *. 7 slots +. slots (#. & 4 pole, 12 slot lap-wound dc armature has two coil sideMslot. &ssuming single turn coil, calculate the %ac9 pitch for progressive and retrogressive winding. &. ( 6 # C. 7 6 ( *. # 6 ( +. ' 6 4 (4. n a 10 pole, lap wound dc armature, the num%er of acve armature conductor per pole is (0. he num%er of compensang conductor per pole re3uired is &. ( C. (0 *. (00 +. 10 ((. & 4 pole dc generator with simple" lap winding has 48 slots and four element per slot. he !u" per pole is 2.( X 106 ma"wells and it turns at 1,(00 rpm. $hat is the output voltage &. '0 volts C. 22( volts *. #'0 volts +. 120 volts ('. & 4 pole dc generator with duple" lap winding has 48 slots and four element per slot. he !u" per pole is 2.( X 106 ma"wells and it turns at 1,(00 rpm. $hat is the output voltage &. '0 volts C. 22( volts *. 480 volts +. 120 volts (7. & separatel/ e"cited generator generates generates 2#0 volts when driven at 1200 rpm, if the !u" is decrese %/ 105. $hat is the new emf with speed remains the same. &. 2#0 volts C. 207 volts *. 2(' volts +. 2(# volts (8. & shunt generator when running light as a motor at 1000 rpm ta9es 12 &mp from 11(-volt mains. he eld current is 7 &mp, and the armature resistance is 0.0# ohm. +etermine stra/-power stra/-power loss of the machine at this parcular value of !e" and speed. &. (74.2( $ C. (7(.2( $ *. (7'.2( $ +. (77.2( $
(. & 20-9$ 220-volt shunt generator has an armature resistance of 0.07 ohm and a shunt resistance of 200 ohms. +etermine the power developed in thEe armature when it delivers its rated output. &. 27. 9$ C.1.2 9$ *. 20.8# 9$ +. 2(.7 9$
'0. he pulle/ of an old gen-set has a diameter of 20 inches. he %elt e"erts a pull of #(# l%s on the pull/ the gen-set runs at 00 rpm. $hat is the appro" 9$ rang of the gen-set &. 7( C. 200 *. 2(0 +. #( '1. &288 volt shunt generator has constant losses of 2880 wa of 12 9$. 9$. Calculate the necessar/ driving tor3ue at rated load in l%-. &. ((80 C. (8#0 *. (280 +. (4'0 '7. & (09$, (00 volt short shunt generator has an armature resistance, series eld resistance and shunt eld resistance are 0.0( ohm, 0.0' ohm and 2(# ohms respecvel/. $hat is the armature power generated &. (1.7' 9$ C. (2.1# 9$ *. 48.74 9$ +. (1.(2 9$
'8. & (0-9$ 4'0-volt shunt generator has a voltage regulaon of 8.7 percent. Calculate the no-load terminal voltage. &. 47( C. (0( *. (00 +. 40 '. wo shunt generators generators & 6 * operates in parallel and their load characteriscs ma/ %e ta9en as straight line. he voltage of generator & fails from 240 volts at no-load to 220 volts at 200 &mp while that of * falls from 24( volts at no-load to 240 volts at 1(0 &mp. +etermine the common terminal voltage when the load is '7 9$. &. 22# volts C. 241 volts *. #22 volts +. #1( volts 70. wo shunt generators generators & 6 *, with rangs of 2(0 and 400 9$ respecvel/ having e3ual no-load voltage of 2'0 volts and full-load voltage of 240 volts, calculate the load of each when the total load shared is '00 9$. &. 2#1 9$ 6 #' 9$ C. 242 9$ 6 #(8 9$ *. 2#8 9$ 6 #'2 9$ +. 2#4 9$ 6 #'' 9$
