In this article, we shared the single-phase induction motors multiple choice questions and answers for electrical and electronics engineers.
Single-Phase Induction Motors Multiple Choice Questions
The below list provides all the multiple-choice questions related to the electrical induction motors.
Answers are available at the bottom of the article.
1. The direction of rotation of a shaded pole motor is determined by
| A) | retentivity of the rotor material |
| B) | interchanging the supply leads |
| C) | none of these answers |
| D) | position of shaded pole with respect to main pole |
2. As hysteresis motors are free from mechanical and magnetic vibrations, therefore, these are considered as suitable for
| A) | sound equipment |
| B) | blowers |
| C) | mixer grinders |
| D) | fans |
3. The value of starting capacitor of a fractional horse-power motor will be
| A) | 400 μF |
| B) | 100 μF |
| C) | 200 μF |
| D) | 300 μF |
4. Which of the following motors is used for the unity power factor?
| A) | Universal motor |
| B) | Hysteresis motor |
| C) | Schrage motor |
| D) | Reluctance motor |
5. The speed control of universal motor used for sewing machines is by
| A) | tapping the field |
| B) | friction |
| C) | centrifugal mechanism |
| D) | varying the resistance |
6. Speed torque characteristic of a repulsion induction motor is similar to that of a D.C.
| A) | series motor |
| B) | compound motor |
| C) | shunt motor |
| D) | separately excited motor |
7. The purpose of the stator winding in the compensated repulsion motor is to
| A) | prevent hunting in the motor |
| B) | improve power factor and provide better speed regulation |
| C) | eliminate armature reaction |
| D) | provide mechanical balance |
8. When a D.C. series motor is connected to A.C. supply, the power factor will be low- because of
| A) | induced current in rotor due to variations of flux |
| B) | none of these answers |
| C) | high inductance of field and armature circuits |
| D) | fine copper wire winding |
9. Which of the following statements regarding reluctance-start motor is incorrect ?
| A) | It is similar to reluctance motor |
| B) | So far as its basic working principle is concerned, it is similar to shaded pole motor |
| C) | the air-gap between rotor and salient poles is non-uniform |
| D) | It is basically an induction motor and not a synchronous one |
10. What could be the size of a universal motor for use in vacuum cleaners?
| A) | 3/4 H.P. |
| B) | 1/4 H.P. |
| C) | 2 H.P. |
| D) | 1 H.P. |
11. The centrifugal switch is used to disconnect starting winding when the motor has
| A) | picked up about 10 to 25 per cent of rated, speed |
| B) | run for about 5 minutes |
| C) | run for about 1 minute |
| D) | picked up about 50 to 70 per cent of rated speed |
12. Which of the following motor will have a relatively higher power factor?
| A) | Capacitor run motor |
| B) | Capacitor start motor |
| C) | Split phase motor |
| D) | Shaded pole motor |
13. The range of efficiency for shaded pole motors is
| A) | 50% to 75% |
| B) | 5% to 35% |
| C) | 80% to 90% |
| D) | 95% to 99% |
14. For ceiling fans generally the single-phase motor used is
| A) | split-phase type |
| B) | permanent capacitor type |
| C) | capacitor start and run type |
| D) | capacitor-start type |
15. If starting winding of a single-phase induction motor is left in the circuit, it will
| A) | run slower |
| B) | run faster |
| C) | draw excessive current and overheat |
| D) | spark at light loads |
16. A reluctance motor
| A) | all of these answers |
| B) | is constant speed motor |
| C) | is self-starting |
| D) | needs no D.C. excitation |
17. In a hysteresis motor, the rotor must have
| A) | resistivity |
| B) | susceptibility |
| C) | none of these answers |
| D) | retentivity |
18. Which motor will make the least noise?
| A) | Universal motor |
| B) | Capacitor motor |
| C) | Shaded-pole motor |
| D) | Hysteresis motor |
19. Shading coils, in case of a shaded pole motor, are used to
| A) | reduce friction losses |
| B) | protect against sparking |
| C) | reduce windage losses |
| D) | produce rotating magnetic field. |
20. If a D.C. series motor is operated on an A.C. supply, it will
| A) | all of these answers |
| B) | spark excessively |
| C) | have poor efficiency |
| D) | have poor power factor |
21. In repulsion motor, maximum torque is developed when
| A) | none of these answers |
| B) | brush axis is at 90° electrical to the field axis |
| C) | brush axis is at 45° electrical to the field axis |
| D) | brush axis coincides with the field axis |
22. In A.C. series motor compensating winding is employed to
| A) | none of these answers |
| B) | reduce sparking at the brushes |
| C) | reduce the effects of armature reaction |
| D) | increase the torque |
23. A.C. series motor as compared to D.C. series motor has
| A) | smaller brush width |
| B) | all of these answers |
| C) | less air gap |
| D) | less-number of field turns |
| E) | more number of armature turns |
24. In a shaded pole motor, the shading coil usually consist of
| A) | a single turn of heavy wire which is in parallel with running winding |
| B) | none of these answers |
| C) | a single turn of heavy copper wire which is short-circuited and carries only induced current |
| D) | a multilayer fine gauge copper wire in parallel with running winding |
25. Centrifugal switch disconnects the auxiliary winding of the motor at about ____percent of synchronous speed
| A) | 30 to 40 |
| B) | 80 to 90 |
| C) | 70 to 80 |
| D) | 100 |
26. Reluctance motors are
| A) | singly excited |
| B) | doubly excited |
| C) | none of these answers |
| D) | either doubly excited or singly excited |
27. A schrage motor can run on
| A) | all of these answers |
| B) | positive slip |
| C) | zero slip |
| D) | negative slip |
28. Short-circuiter is used in
| A) | none of these answers |
| B) | repulsion motor |
| C) | repulsion start induction run motor |
| D) | repulsion induction motor |
29. Which of the following motors would you select for vacuum cleaners?
| A) | Hysteresis motor |
| B) | Repulsion motor |
| C) | Universal motor |
| D) | Reluctance motor |
30. Speed control of a universal motor is achieved by
| A) | applying variable voltage by means of variable autotransformer |
| B) | all of these answers |
| C) | varying field flux with tapped field windings |
| D) | applying variable voltage by means of silicon controlled rectifier |
| E) | connecting rheostat in series |
31. In a split-phase motor the ratio of the number of turns for starting winding to that for running winding is
| A) | more than one |
| B) | less than one |
| C) | two |
| D) | one |
32. A repulsion-start induction-run single phase motor runs as an induction motor only when
| A) | short-circuiter is disconnected |
| B) | stator winding is reversed |
| C) | brushes are shifted to the neutral plane |
| D) | commutator segments are shortcircuited |
33. A universal motor is one which
| A) | runs at dangerously high speed on no-load |
| B) | can be marketed internationally |
| C) | any of these answers |
| D) | can be operated either on D.C. or A.C. supply at approximately the same speed and output |
34. A shaded pole motor does not possess
| A) | commutator |
| B) | all of these answers |
| C) | capacitor |
| D) | centrifugal switch |
35. The electric motor used in portable drills is
| A) | capacitor run motor |
| B) | repulsion motor |
| C) | hysteresis motor |
| D) | universal motor |
36. If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
| A) | current drawn by the motor will be excessively high |
| B) | motor will not come upto speed |
| C) | electrolytic capacitor will, in all probability, suffer break down |
| D) | motor will not carry the load |
37. If a particular application needs high speed and high starting torque, then which of the following motor will be preferred?
| A) | Universal motor |
| B) | Shaded pole type motor |
| C) | Capacitor start motor |
| D) | Capacitor start and run motor |
38. If a single-phase motor runs hot the probable cause cannot be
| A) | high voltage |
| B) | shorted stator coils |
| C) | low voltage |
| D) | blown fuses |
39. Electrical faults in a motor occur most commonly in its
| A) | control equipment |
| B) | commutator |
| C) | motor winding |
| D) | brushes |
40. A universal motor operates on
| A) | approximately constant speed and load |
| B) | constant load and varying speed |
| C) | constant speed and varying load |
| D) | synchronous speed with varying load |
41. Which of the following applications would need the smallest size of motor?
| A) | Sewing machine |
| B) | Table fan |
| C) | Electric clock |
| D) | Domestic mixi |
42. Which of the following statements regarding permanent-split single value capacitor motor is incorrect?
| A) | It is easily reversed because of its low running torque |
| B) | It is more sensitive to voltage variations because of its low running toque |
| C) | It is generally used for exhaust and intake fans and unit-heaters |
| D) | It has very low power factor at full load |
43. Which motor is relatively free from mechanical and magnetic vibrations?
| A) | Reluctance motor |
| B) | Shaded-pole motor |
| C) | Universal motor |
| D) | Hysteresis motor |
44. A single-phase induction motor is
| A) | inherently self-starting with low torque |
| B) | inherently non-self-starting with low torque |
| C) | inherently self-starting with high torque |
| D) | inherently non-self-starting with high torque |
45. If the centrifugal switch does not open at 70 to 80 percent of the synchronous speed of the motor, it would result in
| A) | overloading of running winding |
| B) | damage to the starting winding |
| C) | damage to the centrifugal switch |
| D) | none of the above |
46. For which of the applications a reluctance motor is preferred?
| A) | Signaling and timing devices |
| B) | Lifts and hoists |
| C) | Refrigerators |
| D) | Electric shavers |
47. Direction of rotation of a split-phase motor can be reversed by reversing the connection of
| A) | both running winding only and starting winding only |
| B) | starting winding only |
| C) | running winding only |
| D) | either running winding only or starting winding only |
48. In a capacitor start single-phase motor when the capacitor is replaced by a resistance
| A) | torque will increase |
| B) | motor will continue to run in same direction |
| C) | motor will run in reverse direction |
| D) | the motor will consume less power |
49. In split-phase motor main winding is of
| A) | thick wire placed at the bottom of the slots |
| B) | thick wire placed at the top of thè slots |
| C) | thin wire placed at the bottom of the slots |
| D) | thin wire placed at the top of the slots |
50. In case of high speed universal motor which of the following needs more attention ?
| A) | Air gap |
| B) | Balancing of rotor |
| C) | End play |
| D) | Insulation in rotor |
51. The wattage of the motor for driving a domestic sewing machine will be around
| A) | 10 to 30 W |
| B) | 40 to 75 W |
| C) | 100 to 150 W |
| D) | 5 to 10 W |
52. By pushing and pulling the rotor shaft of a motor, we can check its
| A) | none of these answers |
| B) | side play |
| C) | firmness of mounting |
| D) | free shaft movement |
| E) | end play |
53. Two-value capacitor motor finds increased application as compressor motor in small home air conditioners because
| A) | it is quiet in operation |
| B) | it has an almost non-destructible capacitor |
| C) | it is comparatively cheaper |
| D) | it has low starting as well as running currents at a relatively high power factor |
54. A capacitor selected for capacitor-run motor should be rated for
| A) | r.m.s. voltage |
| B) | none of these answers |
| C) | average voltage |
| D) | peak voltage |
55. In which single-phase motor, the rotor has no teeth or winding?
| A) | Universal motor |
| B) | Hysteresis motor |
| C) | Reluctance motor |
| D) | Split phase motor |
56. The wattage rating for a ceiling fan motor will be in the range
| A) | 250 to 500 W |
| B) | 10 to 20 W |
| C) | 50 to 150 W |
| D) | 200 to 250 W |
57. Which of the following applications make use of a universal motor?
| A) | Portable tools |
| B) | Floor polishing machine |
| C) | Lathe machines |
| D) | Oil expeller |
58. Which of the following statements regarding a reluctance motor is incorrect?
| A) | It cannot be reversed, ordinarily |
| B) | Its squirrel cage-rotor is of unsymmetrical magnetic construction in order to vary reluctance path between stator and rotor |
| C) | It requires no D.C. field excitation for its operation |
| D) | It is nothing else but a single-phase, salient pole synchronous-induction motor |
59. The speed with which the magnetic field of an induction motor rotates is called
| A) | shaft speed |
| B) | slip speed |
| C) | effective speed |
| D) | synchronous speed |
60. Which of the following motors has the highest starting torque?
| A) | Split-phase motor |
| B) | Repulsion motor |
| C) | Capacitor-start motor |
| D) | Shaped pole motor |
61. Starting winding of a single-phase motor of a refrigerator is disconnected from the circuit by means of a
| A) | centrifugal switch |
| B) | none of these answers |
| C) | magnetic relay |
| D) | thermal relay |
62. In a shaded pole motor, the direction of rotation is from
| A) | main pole to shaded pole |
| B) | shaded pole to the main pole |
| C) | none of these answers |
| D) | depends on supply line polarity |
63. Which of the following single-phase induction motors is generally used in time phonographs?
| A) | Resistance start |
| B) | Shaded pole |
| C) | Capacitor start capacitor run |
| D) | Universal |
64. When a universal motor is operated on no-load, its speed is limited by
| A) | weight of the armature |
| B) | windage and friction |
| C) | supply voltage frequency |
| D) | armature reaction |
65. Most of the fractional horsepower motors have either
| A) | ball or roller bearings |
| B) | plain or sleeve bearings |
| C) | hard and annealed bearings |
| D) | soft and porous bearings |
66. In a split phase motor
| A) | the starting winding is connected through a centrifugal switch |
| B) | the running winding is connected through a centrifugal switch |
| C) | the centrifugal switch is used to control supply voltage |
| D) | both starting and running windings are connected through a centrifugal switch |
67. If the ceiling fan, when switched on, runs at a slow speed in the reverse direction, it can be concluded that
| A) | none of these answers |
| B) | the winding has burnt out |
| C) | capacitor is ineffective |
| D) | bearings are worn out |
68. The rotor of the hysteresis motor is made of
| A) | chrome steel |
| B) | aluminum |
| C) | copper |
| D) | cast iron |
69. The motor used for the compressors is
| A) | reluctance motor |
| B) | d.c. series motor |
| C) | shaded pole motor |
| D) | capacitor-start capacitor-run motor |
70. Which motor is normally free from mechanical and magnetic vibrations?
| A) | Split phase motor |
| B) | Hysteresis motor |
| C) | Shaded pole motor |
| D) | Universal motor |
71. In a split phase motor, the running winding should have
| A) | low resistance and high inductance |
| B) | high resistance as well as high inductance |
| C) | low resistance as well as low inductance |
| D) | high resistance and low inductance |
72. The speed of a universal motor is generally reduced by using
| A) | gear trains |
| B) | V-belts |
| C) | chains |
| D) | brakes |
73. A hysteresis motor works on the principle of
| A) | hysteresis loss |
| B) | electromagnetic induction |
| C) | magnetization of rotor |
| D) | eddy current loss |
74. In an A.C. series motor armature coils are usually connected to the commutator
| A) | through capacitors |
| B) | solidly |
| C) | through reactances |
| D) | through resistance |
75. The capacitors used in, single-phase capacitor motors have no
| A) | definite value |
| B) | polarity marking |
| C) | dielectric medium |
| D) | voltage rating |
76. In a ceiling fan employing capacitor run motor
| A) | primary winding surrounds the secondary winding |
| B) | both are usual arrangements |
| C) | none of these answers |
| D) | secondary winding surrounds the primary winding |
77. The starting winding of a single-phase motor is placed in
| A) | stator |
| B) | armature |
| C) | field |
| D) | rotor |
78. Which of the following motors has two separate windings on the motor?
| A) | Repulsion induction motor |
| B) | None of these answers |
| C) | Repulsion motor |
| D) | Repulsion start induction run motor |
79. A shaded pole motor can be used for
| A) | any of these answers |
| B) | toys |
| C) | hair dryers |
| D) | circulators |
80. A single-phase capacitor-start motor will take starting current nearly
| A) | same as full load current |
| B) | four to six times the full load current |
| C) | twice the full load current |
| D) | three times the full load current |
81. The direction of rotation of the universal motor can be reversed by
| A) | interchanging- the brush leads |
| B) | reversing the supply- terminals |
| C) | switching over from A.C. to D.C. |
| D) | any of these answers |
82. In a universal motor, normally the ratio of the width of the brush to the width of commutator segments is
| A) | 2 : 1 |
| B) | 4 : 1 |
| C) | 6 : 1 |
| D) | 1 : 1 |
83. Which of the following motors is generally used in toys?
| A) | Hysteresis motor |
| B) | Two-value capacitor motor |
| C) | Reluctance motor |
| D) | Shaded-pole motor |
84. To reverse the direction of rotation of a capacitor-start motor while it is running we should
| A) | reverse the direction of connections of the auxiliary winding and immediately connect it to supply |
| B) | disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of Main or auxiliary winding |
| C) | disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding |
| D) | reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply |
85. In a hysteresis motor, the rotor
| A) | has high hysteresis loss |
| B) | has high retentivity |
| C) | is made of chrome steel |
| D) | all of these answers |
86. Which motor has an unsymmetrical rotor?
| A) | Universal motor |
| B) | Reluctance motor |
| C) | Shaded-pole motor |
| D) | Split-phase motor |
87. The rotor of which motor does not have winding on it?
| A) | None of these answers |
| B) | Universal motor |
| C) | Reluctance motor |
| D) | Hysteresis motor |
| E) | Repulsion motor |
88. Which of the following applications always have switched on?
| A) | Vacuum cleaners |
| B) | All of these answers |
| C) | Fan motors |
| D) | Pistol drills |
89. A capacitor-start single phase induction motor is switched on to supply with its capacitor replaced by an inductor of equivalent reactance value. It will
| A) | start and run slowly |
| B) | not start at all |
| C) | start and run at rated speed |
| D) | start and then stop |
90. In a shaded-pole single-phase motor, the revolving field is produced by the use of
| A) | inductor |
| B) | resistor |
| C) | capacitor |
| D) | shading coils |
91. Which statement about resistance start split-phase motor is incorrect?
| A) | Starting winding has high resistance but low reactance |
| B) | The main winding has low resistance but high reactance |
| C) | The two stator windings are connected in series across the supply |
| D) | It has two stator windings called main and starting windings |
| E) | It is non-reversible |
92. A repulsion motor is equipped with
| A) | commutator |
| B) | both slip rings and commutator |
| C) | slip rings |
| D) | none of these answers |
93. The speed of a universal motor is usually reduced by using
| A) | gearing |
| B) | belts |
| C) | brakes |
| D) | chains |
94. Which of the following motor will give relatively high starting torque?
| A) | Capacitor start motor |
| B) | Capacitor run motor |
| C) | Split phase motor |
| D) | Shaded pole motor |
95. For the same rating which of the following motors has the highest starting torque ?
| A) | All have identical starting torque |
| B) | Synchronous motor |
| C) | Universal motor |
| D) | Split-phase motor |
96. For a system involving sound recording and reproduction which motor would you select ?
| A) | Shaded-pole motor |
| B) | Hysteresis motor |
| C) | Reluctance motor |
| D) | Universal motor |
97. In split-phase motor auxiliary winding is of
| A) | thin wire placed at the bottom of the slots |
| B) | thin wire placed at the top of the slots |
| C) | thick wire placed at the bottom of the slots |
| D) | thick wire placed at the top of the slots |
98. The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it
| A) | improves the power factor |
| B) | improves the efficiency |
| C) | helps the rotor teeth t,o remain under the stator teeth |
| D) | helps in reducing the tendency of the rotor teeth to remain under the stator teeth |
99. In repulsion motor direction of rotation of motor
| A) | none of these answers |
| B) | is independent of brush shift |
| C) | is the same as that of brush shift |
| D) | is opposite to that of brush shift |
100. Burning out of windings is due to
| A) | short-circuited capacitor |
| B) | capacitor value having changed |
| C) | none of these answers |
| D) | open circuiting of capacitor |
101. A motor gets overheated due to
| A) | worn bearings |
| B) | overloads |
| C) | dry bearings |
| D) | all of these answers |
| E) | shorted winding |
102. In a shaded-pole motor, a rotating magnetic field is produced by using
| A) | shading coils |
| B) | copper windings |
| C) | a capacitor |
| D) | salient poles |
103. Which of the following motors is preferred for tape recorders?
| A) | Two value capacitor motor |
| B) | Universal motor |
| C) | Hysteresis motor |
| D) | Shaded pole motor |
104. The motor used on small lathes is usually
| A) | 3-phase synchronous motor |
| B) | single-phase capacitor run motor |
| C) | D.C. shunt motor |
| D) | universal motor |
105. Which of the following motors-is used in a situation where load increases with speed ?
| A) | Hysteresis motor |
| B) | Induction motor |
| C) | Three-phase series motor |
| D) | Schrage motor |
106. In a capacitor start and run motor the function of the running capacitor in series with the auxiliary winding is to
| A) | to improve torque |
| B) | reduce fluctuations in torque |
| C) | improve power factor |
| D) | increase overload capacity |
107. Which of the following motors is inherently self-starting?
| A) | None of these answers |
| B) | Shaded-pole motor |
| C) | Reluctance motor |
| D) | Split motor |
108. Which of the following statements regarding the single-phase induction motor is correct?
| A) | It can rotate in one direction only |
| B) | It is self-starting |
| C) | It is not self-starting |
| D) | It requires only one winding |
109. In a universal motor, the most common cause of brush sparking is
| A) | high commutator mica |
| B) | open armature winding |
| C) | all of these answers |
| D) | shorted armature winding |
| E) | shorted field winding |
110. When a ceiling fan employing a capacitor run motor is switched on, it hums but does not burn. When it is driven by external means, it runs in whatever direction it is made to run. The trouble is due to
| A) | an open in centrifugal switch |
| B) | an open in capacitor |
| C) | blown fuse |
| D) | short in the capacitor |
111. Which of the following statements about the universal motor is incorrect?
| A) | It is designed for commercial frequency ranging from zero to 60 Hz |
| B) | It is built in small size of up to about 0.5 kW |
| C) | It is usually built into the device it drives |
| D) | Its direction of rotation can be reversed by reversing the polarity of its power supply |
112. In capacitor start single-phase motors
| A) | current in the starting winding is in phase with voltage in running winding |
| B) | current in the starting winding lags the voltage |
| C) | current in the starting winding leads the voltage |
| D) | none of these answers |
113. Hysteresis motor is particularly- useful for high-quality record players and tape recorders because
| A) | it develops hysteresis torque which is extremely steady both in amplitude and phase |
| B) | it can be easily manufactured in extremely small sizes of up to 1 W output |
| C) | it revolves synchronously |
| D) | it is not subject to any magnetic or mechanical vibrations |
114. Single-phase induction motor usually operates on
| A) | unity power factor |
| B) | 0.8 power factor lagging |
| C) | 0.8 power factor leading |
| D) | 0.6 power factor lagging |
115. If the capacitor of a single-phase motor is short-circuited
| A) | the motor will not start |
| B) | the motor will run in the reverse direction |
| C) | the motor will run |
| D) | the motor will run in the same direction at reduced r.p.m. |
116. Which of the following motor will give the highest starting torque?
| A) | Universal motor |
| B) | Schrage motor |
| C) | D.C. shunt motor |
| D) | Repulsion start and induction run motor |
117. The direction of rotation of the universal motor can be reversed by reversing the flow of current through
| A) | armature winding |
| B) | field winding |
| C) | none of these answers |
| D) | either armature winding or field winding |
118. Which of the following statements regarding the repulsion induction motor is incorrect?
| A) | At starting, squirrel-cage winding produces no torque. |
| B) | At start as well as a low speeds, most of the torque is produced by repulsion winding |
| C) | At rated load, it runs at almost synchronous speed |
| D) | It employs centrifugally-operated mechanism to short-circuit the commutator |
119. Which of the following motors is used in mixies?
| A) | Universal motor |
| B) | Reluctance motor |
| C) | Repulsion motor |
| D) | Hysteresis motor |
120. Which of the following Motors can be used for unity power factor?
| A) | Hysteresis motor |
| B) | Schrage motor |
| C) | Capacitor run motor |
| D) | Shaded pole motor |
121. In a two-value capacitor motor, the capacitor used for running purposes is
| A) | paper spaced oil-filled type |
| B) | ceramic type |
| C) | air capacitor |
| D) | a.c. electrolytic type |
122. Which of the following motors will operate at high power factor?
| A) | Capacitor run motor |
| B) | Shaped pole motor |
| C) | Split phase motor |
| D) | Capacitor start motor |
123. The locked rotor current of a shaded pole motor is
| A) | slightly more than full load current |
| B) | less than full load current |
| C) | several times the full load current |
| D) | equal to full load current |
124. If a single-phase induction motor runs slower than normal, the most likely defect is
| A) | worn bearings |
| B) | short-circuit in the winding |
| C) | none of these answers |
| D) | open-circuit in the winding |
125. The repulsion-start induction-run motor is used because of
| A) | minimum cost |
| B) | high starting torque |
| C) | good power factor |
| D) | high efficiency |
126. Which of the following single-phase motors will be cheapest?
| A) | none of these answers |
| B) | Capacitor start motor |
| C) | Capacitor run motor |
| D) | Reluctance motor |
127. The power factor of a single-phase induction motor is usually
| A) | lagging |
| B) | unity |
| C) | unity to 0:8 leading |
| D) | always leading |
128. The shaded pole motor is used for
| A) | low starting torque |
| B) | very high starting torque |
| C) | medium starting torque |
| D) | high starting torque |
129. After the starting winding of a single-phase induction motor is disconnected from the supply, it continues to run only on
| A) | running winding |
| B) | rotor winding |
| C) | compensating winding |
| D) | field winding |
130. Which of the following single-phase motors has relatively poor starting torque ?
| A) | Universal motor |
| B) | All single Phase motors have zero starting torque |
| C) | Capacitor motor |
| D) | Repulsion motor |
131. Which of the following single-phase motors is suitable for timing and control purposes?
| A) | Repulsion motor |
| B) | Universal motor |
| C) | Reluctance motor |
| D) | Series motor |
132. The running winding of a single-phase motor on testing with megger is found to be ground. The most probable location of the ground will be
| A) | at the end terminals |
| B) | anywhere on the winding inside a slot |
| C) | at the slot edge where coil enters or comes out of the slot |
| D) | at the end connections |
133. The speed/load characteristics of a universal motor is same as that of
| A) | A.C. motor |
| B) | D.C. shunt motor |
| C) | none of these answers |
| D) | D.C. series motor |
134. In a repulsion motor, brushes are connected
| A) | to stator winding |
| B) | to starting winding |
| C) | to the external supply |
| D) | together by a jumper wire |
135. Which of the following statements regarding two value capacitor motor is incorrect?
| A) | It has low starting as well as rushing currents |
| B) | It has high starting torque |
| C) | It is preferred to permanent-split single-value capacitor motor where frequent reversals are required |
| D) | It is a reversing motor |
136. In a single-phase motor the centrifugal switch
| A) | reconnects the auxiliary winding of the motor |
| B) | disconnects auxiliary winding of the motor |
| C) | disconnects main winding of the motor |
| D) | reconnects the main winding the motor |
137. A universal motor can run on
| A) | D .C. only |
| B) | none of these answers |
| C) | A.C. only |
| D) | either A.C. or D.C. |
138. Which of the following motors can be run on A.C. as well as D.C. supply?
| A) | Universal motor |
| B) | Reluctance motor |
| C) | Synchronous motor |
| D) | Repulsion motor |
139. In a capacitor start motor, the phase displacement between starting and running winding can be nearly
| A) | 60° |
| B) | 90° |
| C) | 30° |
| D) | 10° |
140. Which type of load is offered by cranes and hoists?
| A) | Reversing, light start |
| B) | Gradually varying load |
| C) | Reversing, heavy start |
| D) | Non-reversing, no-load start |
141. Which of the following statements regarding hysteresis motor is incorrect?
| A) | Its high starting torque is due Lo its high rotor hysteresis loss |
| B) | It is extremely sensitive to fluctuations in supply voltage |
| C) | It is extremely quiet in operation |
| D) | It accelerates from rest to full-speed almost instantaneously |
142. In repulsion motor, zero torque is developed when
| A) | brush axis is 90° electrical to field axis |
| B) | brush axis is 45° electrical to field axis |
| C) | both brush axis coincides with the field axis and brush axis is 90° electrical to field axis |
| D) | brush axis coincides with the field axis |
143. Torque developed by a single-phase induction motor at starting is
| A) | pulsating |
| B) | none of these answers |
| C) | nil |
| D) | uniform |
144. Which of the following motors is used in tape recorders?
| A) | Universal motor |
| B) | Hysteresis motor |
| C) | Capacitor-run motor |
| D) | Reluctance motor |
145. The rotor developed by a single-phase motor at starting is
| A) | zero |
| B) | rated torque |
| C) | more than the rated torque |
| D) | less than the rated torque |
146. Which of the following is the most economical method of starting a single-phase induction motor?
| A) | Resistance-start method |
| B) | Split-phase method |
| C) | Inductance-start method |
| D) | Capacitance-start method |
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