Single Phase Induction Motors -- MCQ with Answers

Single Phase Induction Motors -- MCQ with Answers
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1. In a split phase motor, the running winding should have
(a)    high resistance and low inductance
(b)    low resistance and high inductance
(c)    high resistance as well as high inductance
(d)    low resistance as well as low inductiance
Ans: b

2.    If the capacitor of a single-phase motor is short-circuited
(a)    the motor will not start
(b)    the motor will run
(c)    the motor will run in reverse direction
(d)    the motor will run in the same direction at reduced r.p.m.
Ans: a

3.    In capacitor start single-phase motors
(a)    current in the starting winding leads the voltage
(b)    current in the starting winding lags the voltage
(c)    current in the starting winding is in phase with voltage in running winding
(d)    none of the above
Ans: a

4.    In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to
(a)    improve power factor
(b)    increase overload capacity
(c)    reduce fluctuations in torque
(d)    to improve torque
Ans: a

5.    In a capacitor start motor, the phase displacement between starting and running winding can be nearly
(a)  10°   
(b) 30°
(c) 60°   
(d) 90°
Ans: d

6.    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)    both starting and running windings are connected through a centrifugal switch
(d)     centrifugal switch is used to control supply voltage
Ans: a

7.    The rotor developed by a single-phase motor at starting is
(a)     more than i.he rated torque
(b)     rated torque
(c)    less than the rated torque
(d)    zero
Ans: d

8.    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
Ans: a

9.    Which of the following motor will have relatively higher power factor ?
(a)    Capacitor run motor
(b)    Shaded pole motor
(c)    Capacitor start motor
(d)    Split phase motor
Ans: a

10.    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) a single turn of heavy copper wire which is short-circuited and carries only induced current
(c) a multilayer fine gauge copper wire in parallel with running winding
(d) none of the above
Ans: b

11.    In a shaded pole single-phase motor, the revolving field is produced by the use of
(a) inductor   
(b) capacitor
(c) resistor   
(d) shading coils
Ans: d

12.    A centrifugal switch is used to dis- connect 'starting winding when motor has
(a)     run for about 1 minute
(b)     run for about 5 minutes
(c)    picked up about 50 to 70 per cent of rated speed
(d)    picked up about 10 to 25 per cent of rated speed
Ans: c

13.    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
Ans: a

14.    The value of starting capacitor of a fractional horse power motor will be
(a) 100 uF   
(6) 200 uF
(c) 300 uF   
(d) 400 uF
Ans: c
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15.    In repulsion motor direction of rotation of motor
(a) is opposite to that of brush shift
(b) is the same as that of brush shift
(c) is independent of brush shift
Ans: b

16.    In a single phase motor the centrifugal switch
(a)     disconnects auxiliary winding of the motor
(b)     disconnects main winding of the motor
(c)    reconnects the main winding the motor
(d)    reconnects the auxiliary winding of the motor
Ans: a

17.    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
(a) at the end connections
(b) at the end terminals
(c) anywhere on the winding inside a slot
(d) at the slot edge where coil enters or comes out of the slot
Ans: d

18.    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 then stop
(b)    start and run slowly
(c)    start and run at rated speed
(d)    not start at all
Ans: d

19.    Which of the following motors is used in mixies ?
(a) Repulsion motor
(b) Reluctance motor
(c) Hysteresis motor
(d) Universal motor
Ans: d

20.    Which of the following motors is inherently self starting ?
(a)    Split motor
(b)    Shaded-pole motor
(c)    Reluctance motor
(d)     None of these
Ans: b

21.    The direction of rotation of an hysteresis motor is determined by
(a) interchanging the supply leads
(b) position of shaded pole with respect to main pole
(c) retentivity of the rotor material
(d) none of these
Ans: b

22.    Burning out of windings is due to
(a)     short circuited capacitor
(b)     capacitor value hiving changed
(c)    open circuiting of capacitor
(d)    none of the above
Ans: a

23.    Direction of rotation of a split phase motor can be reversed by reversing the connection of
(a) running winding only
(b) starting winding only
(c) either (a) or (b)
(d) both (a) and (b)
Ans: c

24.    Short-circuiter is used in
(a)    repulsion induction motor
(b)    repulsion motor
(c)    repulsion start induction run motor
(d)    none of the above
Ans: c

25.    The range of efficiency for shaded pole motors is
(a) 95% to 99%      
(b) 80% to 90%
(c) 50% to 75%      
(d) 5% to 35%
Ans: d

26.    In a capacitor start single-phase motor, when capacitor is replaced by a resistance
(a)    torque will increase
(b)    the motor will consume less power
(c)    motor will run in reverse direction
(d)    motor will continue to run in same direction
Ans: d

27.    The power factor of a single-phase induction motor is usually
(a)     lagging   
(b)     always leading
(c)    unity
(d)    unity to 0.8 leading
Ans: a

28.    A shaded pole motor can be used for
(a) toys   
(b) hair dryers
(c) circulators   
(d) any of the above
Ans: d

29.    A hysteresis motor works on the principle of
(a)     hysteresis loss
(b)     magnetisation of rotor
(c)    eddy current loss
(d)    electromagnetic induction
Ans: a

30.    Which of the following motor will give the highest starting torque ?
(a)     D.C. shunt motor
(b)     Schrage motor
(c)    Repulsion start and induction run motor
(d)    Universal motor
Ans: b

31.    For which of the applications a reluctance motor is preferred ?
(a)     Electric shavers
(b)     Refrigerators
(c)    Signalling and timing devices
(d)    Lifts and hoists
Ans: c

32.    The motor used on small lathes is usually
(a)     universal motor
(b)     D.C. shunt motor
(c)    single-phase capacitor run motor
(d)    3-phase synchronous motor
Ans: c
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33.    Which of the following motors is preferred for tape-recorders ?
(a)    Shaded pole motor
(b)    Hysteresis motor
(c)    Two value capacitor motor
(d)    Universal motor
Ans: b

34.    A single-phase induction motor is
(a)     inherently self-starting with high torque
(b)     inherently self-starting with low torque
(c)    inherently non-self-starting with low torque
(d)    inherently non-self-starting with high torque
Ans: c

35.    A schrage motor can run on
(a) zero slip   
(b) negative slip
(c) positive slip      
(d) all of the above
Ans: d

36.    A universal motor can run on
(a)     A.C. only
(6)     D.C. only
(c)    either A.C. or D.C.
(d)    none of the above
Ans: c

37.    Which of the following single-phase motors is suitable for timing and control purposes ?
(a)     Reluctance motor
(b)     Series motor
(c)    Repulsion motor
(d)    Universal motor
Ans: a

38.    Single phase induction motor usually operates on
(a)     0.6 power factor lagging
(b)     0.8 power factor lagging
(c)    0.8 power factor leading
(d)    unity power factor
Ans: a

39.    In split-phase motor iauxiliary winding is of
(a)    thick wire placed at the bottom of the slots
(b)    thick wire placed at the top of the slots
(c)    thin wire placed at the top of the slots
(d)    thin wire placed at the bottom of the slots
Ans: c

40.    Which of the following motors will operate at high power factor ?
(a)    Shaped pole motor
(b)    Split phase motor
(c)    Capacitor start motor
(d)    Capacitor run motor
Ans: d

41.    In a two value capacitor motor, the capacitor used for running purposes is
(a)    air capacitor
(b)    paper spaced oilfilled type
(c)    ceramic type
(d)    a.c. electrolytic type
Ans: b

42.    Which of the following motors can be run on AC. as well as D.C. supply ?
(a)    Universal motor
(b)    Repulsion motor
(c)    Synchronous motor
(d)    Reluctance motor
Ans: a

43.    In A.C. series motor compensating winding is employed to
(a)    reduce the effects of armature reaction
(b)    increase the torque
(c)    reduce sparking at the brushes
(d)    none of the above
Ans: c
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44.    Which of the following single-phase induction motors is generally used in time phonographs ?
(a)    Resistance start
(b)    Capacitor start capacitor run
(c)    Shaded pole
(d)     Universal
Ans: c

45.    Which of the following motors has highest starting torque ?
(a)    Repulsion motor
(b)    Shaped pole motor
(c)    Capacitor-start motor
(d)    Split-phase motor
Ans: c

46.    The repulsion-start induction-run motor is used because of
(a)    good power factor
(b)    high efficiency
(c)    minimum cost
(d)    high starting torque
Ans: d

47.    In case of a shaded pole motor the direction of rotation of the motor is
(a)    from main pole to shaded pole
(b)    from shaded pole to main pole
(c)    either of the above depending on voltage
(d)    either of the above depending on power factor
Ans: a

48.    In case of high speed universal motor which of the following needs more attention ?
(a)     End play   
(b)     Air gap
(c)    Insulation in rotor
(d)    Balancing of rotor
Ans: d

49.    The wattage rating for a ceiling fan motor will be in the range
(a) 200 to 250 W   
(b) 250 to 500 W
(c) 50 to 150 W      
(d) 10 to 20 W
Ans: c

50.    The wattage of motor for driving domestic sewing machine will be around
(a) 100 to 150 W   
(b) 40 to 75 W
(c) 10 to 30 W   
(d) 5 to 10 W
Ans: a

51.    Which of the following single-phase motors has relatively poor starting torque ?
(a)    Universal motor
(b)    Repulsion motor
(c)    Capacitor motor
(d)    All single phase motors have zero starting torque
Ans: c

52.    Which type of load is offered by cranes and hoists ?
(a)     Gradually varying load
(b)     Non-reversing, no-load start
(c)    Reversing, light start
(d)    Reversing, heavy start
Ans: d

53.    The speed of a universal motor is generally reduced by using
(a) gear trains       
(b) V-belts
(c) brakes   
(d) chains
Ans: a

54.    Which of the following motors can be used for unity power factor ?
(a)    Capacitor run motor
(b)    Shaded pole motor
(c)    Hysteresis motor
(d)    Schrage motor
Ans: d

55.    When a D.C. series motor is connected to A.C. supply, the power factor will be low because of
(a)    high inductance of field and armature circuits
(b)    induced current in rotor due to variations of flux
(c)    fine copper wire winding
(d)    none of the above
Ans: a

56.    The direction of rotation of universal motor can be reversed the by reversing the flow of current through
(a)    armature winding
(b)    field winding
(c)    either armature winding or field winding
(d)    none of the above
Ans: c

57.    In which single-phase motor, the rotor has no teeth or winding ?
(a)    Split phase motor
(b)    Reluctance motor
(c)    Hysteresis motor
(d)    Universal motor
Ans: c

58.    Which motor is normally free from mechanical and magnetic vibrations ?
(a)    Split phase motor
(b)    Universal motor
(c)    Hysteresis motor
(d)    Shaded pole motor
Ans: c

59.    As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for
(a)    fans
(b)    blowers
(c)    sound equipment
(d)    mixer grinders
Ans: c

60.    A reluctance motor
(a)    is self-starting
(b)    is constant speed motor
(c)    needs no D.C. excitation
(d)    all of the above
Ans: d

61.    In a hysteresis motor, the rotor must have
(a)    retentivity
(b)    resistivity
(c)    susceptibility
(d)     none of the above
Ans: a

62.    The rotor of a hysteresis motor is made of
(a) aluminium       
(b) cast iron
(c) chrome steel     
(d) copper
Ans: c

63.    The electric motor used in portable drills is
(a)    capacitor run motor
(b)    hysteresis motor
(c)    universal motor
(d)    repulsion motor
Ans: c

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