Quiz  /  Single Phase Induction Motors Electrical Engineering MCQ Questions and Answers PDF

  • 1. 
    In a split phase motor, the running winding should have

  • high resistance and low inductance
  • low resistance and high inductance
  • high resistance as well as high inductance
  • low resistance as well as low inductiance

  • 2. 
    If the capacitor of a single-phase motor is short-circuited

  • the motor will not start
  • the motor will run
  • the motor will run in reverse direction
  • the motor will run in the same direction at reduced r.p.m.

  • 3. 
    In capacitor start single-phase motors

  • current in the starting winding leads the voltage
  • current in the starting winding lags the voltage
  • current in the starting winding is in phase with voltage in running winding
  • none of the above

  • 4. 
    In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to

  • improve power factor
  • increase overload capacity
  • reduce fluctuations in torque
  • to improve torque

  • 5. 
    In a capacitor start motor, the phase displacement between starting and running winding can be nearly

  • 10°
  • 30°
  • 60°
  • 90°

  • 6. 
    In a split phase motor

  • the starting winding is connected through a centrifugal switch
  • the running winding is connected through a centrifugal switch
  • both starting and running windings are connected through a centrifugal switch
  • centrifugal switch is used to control supply voltage

  • 7. 
    The rotor developed by a single-phase motor at starting is

  • more than i.he rated torque
  • rated torque
  • less than the rated torque
  • zero

  • 8. 
    Which of the following motor will give relatively high starting torque ?

  • Capacitor start motor
  • Capacitor run motor
  • Split phase motor
  • Shaded pole motor

  • 9. 
    Which of the following motor will have relatively higher power factor ?

  • Capacitor run motor
  • Shaded pole motor
  • Capacitor start motor
  • Split phase motor

  • 10. 
    In a shaded pole motor, the shading coil usually consist of

  • a single turn of heavy wire which is in parallel with running winding
  • a single turn of heavy copper wire which is short-circuited and carries only induced current
  • a multilayer fine gauge copper wire in parallel with running winding
  • none of the above

  • 11. 
    In a shaded pole single-phase motor, the revolving field is produced by the use of

  • inductor
  • capacitor
  • resistor
  • shading coils

  • 12. 
    A centrifugal switch is used to dis- connect ‘starting winding when motor has

  • run for about 1 minute
  • run for about 5 minutes
  • picked up about 50 to 70 per cent of rated speed
  • picked up about 10 to 25 per cent of rated speed

  • 13. 
    If a particular application needs high speed and high starting torque, then which of the following motor will be  referred ?

  • Universal motor
  • Shaded pole type motor
  • Capacitor start motor
  • Capacitor start and run motor

  • 14. 
    In a single phase motor the centrifugal switch

  • disconnects auxiliary winding of the motor
  • disconnects main winding of the motor
  • reconnects the main winding the motor
  • reconnects the auxiliary winding of the motor

  • 15. 
    The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be

  • at the end connections
  • at the end terminals
  • anywhere on the winding inside a slot
  • at the slot edge where coil enters or comes out of the slot

  • 16. 
    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

  • start and then stop
  • start and run slowly
  • start and run at rated speed
  • not start at all

  • 17. 
    Which of the following motors is used in mixies ?

  • Repulsion motor
  • Reluctance motor
  • Hysteresis motor
  • Universal motor

  • 18. 
    Which of the following motors is inherently self starting ?

  • Split motor
  • Shaded-pole motor
  • Reluctance motor
  • None of these

  • 19. 
    The direction of rotation of an hysteresis motor is determined by

  • interchanging the supply leads
  • position of shaded pole with respect to main pole
  • retentivity of the rotor material
  • none of these

  • 20. 
    Burning out of winding is due to

  • short circuited capacitor
  • capacitor value hiving changed
  • open circuiting of capacitor
  • none of the above

  • 21. 
    Direction of rotation of a split phase motor can be reversed by reversing the connection of

  • running winding only
  • starting winding only
  • either (a) or (b)
  • both (a) and (b)

  • 22. 
    Short-circuiter is used in

  • repulsion induction motor
  • repulsion motor
  • repulsion start induction run motor
  • none of the above

  • 23. 
    The range of efficiency for shaded pole motors is

  • 95% to 99%
  • 80% to 90%
  • 50% to 75%
  • 5% to 35%

  • 24. 
    In a capacitor start single-phase motor, when capacitor is replaced by a resistance

  • torque will increase
  • the motor will consume less power
  • motor will run in reverse direction
  • motor will continue to run in same direction

  • 25. 
    The power factor of a single-phase induction motor is usually

  • lagging
  • always leading
  • unity
  • unity to 0.8 leading

  • 26. 
    A shaded pole motor can be used for

  • toys
  • hair dryers
  • circulators
  • any of the above

  • 27. 
    A hysteresis motor works on the principle of

  • hysteresis loss
  • magnetisation of rotor
  • eddy current loss
  • electromagnetic induction

  • 28. 
    Which of the following motor will give the highest starting torque ?

  • D.C. shunt motor
  • Schrage motor
  • Repulsion start and induction run motor
  • Universal motor

  • 29. 
    For which of the applications a reluctance motor is preferred ?

  • Electric shavers
  • Refrigerators
  • Signalling and timing devices
  • Lifts and hoists

  • 30. 
    The motor used on small lathes is usually

  • universal motor
  • D.C. shunt motor
  • single-phase capacitor run motor
  • 3-phase synchronous motor

  • 31. 
    Which of the following motors is preferred for tape-recorders ?

  • Shaded pole motor
  • Hysteresis motor
  • Two value capacitor motor
  • Universal motor

  • 32. 
    A single-phase induction motor is

  • inherently self-starting with high torque
  • inherently self-starting with low torque
  • inherently non-self-starting with low torque
  • inherently non-self-starting with high torque

  • 33. 
    A schrage motor can run on

  • zero slip
  • negative slip
  • positive slip
  • all of the above

  • 34. 
    Which of the following single-phase motors is suitable for timing and control purposes ?

  • Reluctance motor
  • Series motor
  • Repulsion motor
  • Universal motor

  • 35. 
    Single phase induction motor usually operates on

  • 0.6 power factor lagging
  • 0.8 power factor lagging
  • 0.8 power factor leading
  • unity power factor

  • 36. 
    In split-phase motor auxiliary winding is of

  • thick wire placed at the bottom of the slots
  • thick wire placed at the top of the slots
  • thin wire placed at the top of the slots
  • thin wire placed at the bottom of the slots

  • 37. 
    Which of the following motors will operate at high power factor ?

  • Shaped pole motor
  • Split phase motor
  • Capacitor start motor
  • Capacitor run motor

  • 38. 
    In a two value capacitor motor, the capacitor used for running purposes is

  • air capacitor
  • paper spaced oil filled type
  • ceramic type
  • a.c. electrolytic type

  • 39. 
    Which of the following motors can be run on AC. as well as D.C. supply ?

  • Universal motor
  • Repulsion motor
  • Synchronous motor
  • Reluctance motor

  • 40. 
    In A.C. series motor compensating winding is employed to

  • reduce the effects of armature reaction
  • increase the torque
  • reduce sparking at the brushes
  • none of the above

  • 41. 
    Which of the following single-phase induction motors is generally used in time phonographs ?

  • Resistance start
  • Capacitor start capacitor run
  • Shaded pole
  • Universal

  • 42. 
    Which of the following motors has highest starting torque ?

  • Repulsion motor
  • Shaped pole motor
  • Capacitor-start motor
  • Split-phase motor

  • 43. 
    The repulsion-start induction-run motor is used because of

  • good power factor
  • high efficiency
  • minimum cost
  • high starting torque

  • 44. 
    In case of a shaded pole motor the direction of rotation of the motor is

  • from main pole to shaded pole
  • from shaded pole to main pole
  • either of the above depending on voltage
  • either of the above depending on power factor

  • 45. 
    In case of high speed universal motor which of the following needs more attention ?

  • End play
  • Air gap
  • Insulation in rotor
  • Balancing of rotor

  • 46. 
    The wattage rating for a ceiling fan motor will be in the range

  • 200 to 250 W
  • 250 to 500 W
  • 50 to 150 W
  • 10 to 20 W

  • 47. 
    The wattage of motor for driving domestic sewing machine will be around

  • 100 to 150 W
  • 40 to 75 W
  • 10 to 30 W
  • 5 to 10 W

  • 48. 
    Which of the following single-phase motors has relatively poor starting torque ?

  • Universal motor
  • Repulsion motor
  • Capacitor motor
  • All single phase motors have zero starting torque

  • 49. 
    Which type of load is offered by cranes and hoists ?

  • Gradually varying load
  • Non-reversing, no-load start
  • Reversing, light start
  • Reversing, heavy start

  • 50. 
    The speed of a universal motor is generally reduced by using

  • gear trains
  • V-belts
  • brakes
  • chains

  • 51. 
    Which of the following motors can be used for unity power factor ?

  • Capacitor run motor
  • Shaded pole motor
  • Hysteresis motor
  • Schrage motor

  • 52. 
    When a D.C. series motor is connected to A.C. supply, the power factor will be low because of

  • high inductance of field and armature circuits
  • induced current in rotor due to variations of flux
  • fine copper wire winding
  • none of the above

  • 53. 
    The direction of rotation of universal motor can be reversed the by reversing the flow of current through

  • armature winding
  • field winding
  • either armature winding or field winding
  • none of the above

  • 54. 
    In which single-phase motor, the rotor has no teeth or winding ?

  • Split phase motor
  • Reluctance motor
  • Hysteresis motor
  • Universal motor

  • 55. 
    Which motor is normally free from mechanical and magnetic vibrations ?

  • Split phase motor
  • Universal motor
  • Hysteresis motor
  • Shaded pole motor

  • 56. 
    As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for

  • fans
  • blowers
  • sound equipment
  • mixer grinders

  • 57. 
    A reluctance motor

  • is self-starting
  • is constant speed motor
  • needs no D.C. excitation
  • all of the above

  • 58. 
    In a hysteresis motor, the rotor must have

  • retentivity
  • resistivity
  • susceptibility
  • none of the above

  • 59. 
    The rotor of a hysteresis motor is made of

  • aluminium
  • cast iron
  • chrome steel
  • copper

  • 60. 
    The electric motor used in portable drills is

  • capacitor run motor
  • hysteresis motor
  • universal motor
  • repulsion motor

  • 61. 
    Which of the following applications always have some load whenever switched on ?

  • Vacuum cleaners
  • Fan motors
  • Pistol drills
  • All of the above

  • 62. 
    The speed control of universal motor used for sewing machines is by

  • friction
  • varying the resistance
  • tapping the field
  • centrifugal mechanism

  • 63. 
    Torque developed by a single phase induction motor at starting is

  • pulsating
  • uniform
  • none of the above
  • nil

  • 64. 
    In split phase motor main winding is of

  • thin wire placed at the top of the slots
  • thin wire placed at the bottom of the slots
  • thick wire placed at the bottom of the slots
  • thick wire placed at the top of the” slots

  • 65. 
    In repulsion motor, maximum torque is developed when

  • brush axis is at 45° electrical to the field axis
  • brush axis coincides with the field axis
  • brush axis is at 90° electrical to the field axis
  • none of the above

  • 66. 
    If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in

  • damage to the starting winding
  • damage to the centrifugal switch
  • overloading of running winding
  • none of the above

  • 67. 
    Speed torque characteristic of a repulsion induction motor is similar to that of a D.C.

  • shunt motor
  • series motor
  • compound motor
  • separately excited motor

  • 68. 
    In a ceilingfan employing capacitor run motor

  • secondary winding surrounds the primary winding
  • primary winding surrounds the secondary winding
  • both are usual arrangements
  • none of the above

  • 69. 
    The shaded pole motor is used for

  • high starting torque
  • low starting torque
  • medium starting torque
  • very high starting torque

  • 70. 
    The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it

  • improves the efficiency
  • helps the rotor teeth to remain under the stator teeth
  • helps in reducing the tendency of the rotor teeth to remain under the stator teeth
  • improves the power factor

  • 71. 
    The speed/load characteristics of a universal motor is same as that of

  • A.C. motor
  • D.C. shunt motor
  • D.C. series motor
  • none of the above

  • 72. 
    The purpose of stator winding in the compensated repulsion motor is to

  • provide mechanical balance
  • improve power factor and provide better speed regulation
  • prevent hunting in the motor
  • eliminate armature reaction

  • 73. 
    Which of the following motors is used for unity power factor ?

  • Hysteresis motor
  • Schrage motor
  • Universal motor
  • Reluctance motor

  • 74. 
    The motor used for the compressors is

  • d.c. series motor
  • shaded pole motor
  • capacitor-start capacitor-run motor
  • reluctance motor

  • 75. 
    Which of the following motors is used in a situation where load increases with speed ?

  • Induction motor
  • Three-phase series motor
  • Schrage motor
  • Hysteresis motor

  • 76. 
    In repulsion motor, zero torque is developed when

  • brush axis is 45° electrical to field axis
  • brush axis coincides with the field axis
  • brush axis is 90° electrical to field axis
  • both (b) and (c)

  • 77. 
    Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed

  • 30 to 40
  • 70 to 80
  • 80 to 90
  • 100

  • 78. 
    Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a

  • magnetic relay
  • thermal relay
  • centrifugal switch
  • none of the above

  • 79. 
    If a single phase induction motor runs slower than normal, the most likely defect is

  • worn bearings
  • short-circuit in the winding
  • open-circuit in the winding
  • none of the above

  • 80. 
    Which of the following motors is used in tape-recorders ?

  • Hysteresis motor
  • Reluctance motor
  • Capacitor-run motor
  • Universal motor

  • 81. 
    Which of the following statements regarding two value capacitor motor is incorrect ?

  • It is a reversing motor
  • It is preferred to permanent-split single-value capacitor motor where frequent reversals are required
  • It has low starting as well as rushing currents
  • It has high starting torque

  • 82. 
    Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because

  • it is comparatively cheaper
  • it has almost non-destructible capacitor
  • it has low starting as well as running currents at relatively high power factor
  • it is quiet in operation

  • 83. 
    If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then

  • motor will not come up to speed
  • motor will not carry the load
  • current drawn by the motor will be excessively high
  • electrolytic capacitor will, in all probability, suffer break down

  • 84. 
    In a universal motor, the most common cause of brush sparking is

  • open armature winding
  • shorted armature winding
  • shorted field winding”
  • high commutator mica
  • all of the above

  • 85. 
    If starting winding of a single-phase induction motor is left in the circuit, it will

  • run faster
  • spark at light loads
  • draw excessive current and overheat
  • run slower

  • 86. 
    Most of the fractional horsepower motors have either

  • hard and annealed bearings
  • ball or roller bearings
  • soft and porous bearings
  • plain or sleeve bearings

  • 87. 
    Which of the following statements regarding reluctance-start motor is incorrect ?

  • It is similar to reluctance motor
  • It is basically an induction motor and not a synchronous one
  • So far as its basic working principle is concerned, it is similar to shaded pole motor
  • the air-gap between rotor and salient poles is non- uniform

  • 88. 
    To reverse the direction of rotation of acapacitor start motor while it is running we should

  • disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
  • disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding
  • reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply
  • reverse the direction of connections of the auxiliary winding and immediately connect it to supply

  • 89. 
    In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will

  • become unstable
  • draw excessive armature current and may burn out
  • fall out of synchronism and come to stand still
  • run as induction motor

  • 90. 
    Which of the following motors has two separate windings on the motor ?

  • Repulsion motor
  • Repulsion induction motor
  • Repulsion start induction run motor
  • None of the above

  • 91. 
    A shaded pole motor does not possess

  • centrifugal switch
  • capacitor
  • commutator
  • all of the above

  • 92. 
    In a A.C. series motor armature coils are usually connected to commutator

  • through resistance
  • through reactances
  • through capacitors
  • solidly

  • 93. 
    Which of the following statements regarding a reluctance motor is incorrect ?

  • It cannot be reversed, ordinarily
  • It requires no D.C. field excitation for its operation
  • It is nothing else but a single-phase, salient pole synchronous-induction motor
  • Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluctance path between stator and rotor

  • 94. 
    A repulsion motor is equipped with

  • slip rings
  • commutator
  • both (a) and (b)
  • none of the above

  • 95. 
    The capacitors used in single-phase capacitor motors have no

  • voltage rating
  • dielectric medium
  • polarity marking
  • definite value

  • 96. 
    . If a D.C. series motor is operated on A.C. supply, it will

  • spark excessively
  • have poor efficiency
  • have poor power factor
  • all of the above

  • 97. 
    . After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on

  • running winding
  • rotor winding
  • field winding
  • compensating winding

  • 98. 
    . Which of the following statements regarding repulsion-start induction motor is incorrect ?

  • It requires more maintenance of commutator and other mechanical devices
  • It makes quite a bit of noise on starting
  • In fractional horse power motors, it has replaced the capacitor motors
  • It is not easily reversed

  • 99. 
    . A.C. series motor as compared to D.C. series motor has

  • smaller brush width
  • less number of field turns
  • more number of armature turns
  • less air gap
  • all of the above

  • 100. 
    . Locked rotor current of a shaded pole motor is

  • equal to full load current
  • less than full load current
  • slightly more than full load current
  • several times the full load current

  • 101. 
    . Speed control of a universal motor is achieved by

  • varying field flux with tapped field windings
  • connecting rheostat in series
  • applying variable voltage by means of silicon controlled rectifier
  • applying variable voltage by means of variable auto-transformer
  • all of the above methods

  • 102. 
    . Hysteresis motor is particularly useful for high-quality record players and tape-recorders because

  • it revolves synchronously
  • it is not subject to any magnetic or mechanical vibrations
  • it can be easily manufactured in extremely small sizes of up to 1 W output
  • it develops hysteresis torque which is extremely steady both in amplitude and phase

  • 103. 
    . Which of the following statements regarding hysteresis motor is in incorrect ?

  • It is extremely sensitive to fluctuations in supply voltage
  • Its high starting torque is due to its high rotor hysteresis loss
  • It is extremely quiet in operation
  • It accelerates from rest to full-speed almost instantaneously

  • 104. 
    . Which of the following statements regarding single-phase induction motoris correct ?

  • It requires only one winding
  • It can rotate in one direction only
  • It is self-starting
  • It is not self-starting

  • 105. 
    . The starting winding of a single-phase motor is placed in

  • armature
  • field
  • rotor
  • stator

  • 106. 
    . The speed of a universal motor is usually reduced by using

  • gearing
  • belts
  • brakes
  • chains
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