electrical

Synchronous Motor MCQ Questions and Answers Page - 4

1.

The synchronous motor can be started by

Answer/ Hint      

Answer : D

Explanation :

2.

The number of poles on a pony motor employ head for starting of a 3-phase synchronous motor should be ____that on the synchronous motor.

Answer/ Hint      

Answer : C

Explanation :

3.

When a synchronous motor is started, the filed winding is energized

Answer/ Hint      

Answer : B

Explanation :

4.

A 3-phase synchronous motor provided with damper winding is started as a 3-phase

Answer/ Hint      

Answer : C

Explanation :

5.

A cylindrical rotor synchronous motor is switched on to the dc supply with its field windings shorted on themselves. it will

Answer/ Hint      

Answer : B

Explanation :

6.

If the filed winding of a synchronous motor is short circuited and the motor stator is connected to 3-phase ac supply through an auto transformer, the motor will

Answer/ Hint      

Answer : A

Explanation :

7.

While starting a synchronous motor its field winding should be

Answer/ Hint      

Answer : B

Explanation :

8.

Synchronous motors are inherently not self-starting motors as

Answer/ Hint      

Answer : A

Explanation :

9.

Electrical machines (ac) should have proper____ in order to limit the operating temperature

Answer/ Hint      

Answer : B

Explanation :

10.

during short circuit test on a synchronous motor ____ is / are short circuited

Answer/ Hint      

Answer : A

Explanation :

11.

The rotor copper losses of a synchronous motor are met by ____

Answer/ Hint      

Answer : B

Explanation :

12.

The efficiency of a properly designed synchronous machine is of the order of

Answer/ Hint      

Answer : C

Explanation :

13.

The negative phase sequence in a 3-phase synchronous motor exists when the motor is

Answer/ Hint      

Answer : C

Explanation :

14.

In case one phase of a 3-phase synchronous motor is short circuited the motor will

Answer/ Hint      

Answer : D

Explanation :

15.

A synchronous motor may fail to pull into synchronous owing to

Answer/ Hint      

Answer : D

Explanation :

16.

Which of the following is not the advantage of a synchronous motor?

Answer/ Hint      

Answer : D

Explanation :

17.

Which of the following synchronous motors has cost comparable to that of an induction motor?

Answer/ Hint      

Answer : B

Explanation :

18.

A 3-phase synchronous motor is widely used for

Answer/ Hint      

Answer : D

Explanation :

19.

Synchronous motors are not used

Answer/ Hint      

Answer : C

Explanation :

20.

In a synchronous motor, the magnitude of a stator back e.m.f Eb depends upon

Answer/ Hint      

Answer : B

Explanation :

21.

A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed

Answer/ Hint      

Answer : B

Explanation :

22.

The magnitude of field flux in a 3-phase synchronous motor

Answer/ Hint      

Answer : A

Explanation :

23.

The torque angle, in asynchronous motor, is the angle between

Answer/ Hint      

Answer : C

Explanation :

24.

Hunting in the synchronous motor cannot be due to

Answer/ Hint      

Answer : A

Explanation :

25.

By which of the following methods the constant speed of synchronous motor can be changed to new flux value?

Answer/ Hint      

Answer : A

Explanation :

26.

In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. the motor speed will be

Answer/ Hint      

Answer : B

Explanation :

27.

A synchronous motor connected to infinite bus-bar has at constant full load, 100 % excitation and unity power factor. On changing the excitation only the armature current will be

Answer/ Hint      

Answer : D

Explanation :

28.

Which of the following motors is non self-starting?

Answer/ Hint      

Answer : B

Explanation :

29.

In asynchronous motor the back e.m.f generated in the armature at no load is approximately equal to the applied voltage, then

Answer/ Hint      

Answer : D

Explanation :

30.

In asynchronous motor, the damping winding is generally used to

Answer/ Hint      

Answer : A

Explanation :

31.

If the field of a synchronous motor is under-excited, the power factor will be

Answer/ Hint      

Answer : C

Explanation :

32.

The back e.m.f in the stator of the synchronous motor depends upon

Answer/ Hint      

Answer : D

Explanation :

33.

The maximum value of torque that a synchronous motor can develop without loosing its synchronism, is known as

Answer/ Hint      

Answer : D

Explanation :

34.

In a synchronous motor, armature current has large values for

Answer/ Hint      

Answer : C

Explanation :

35.

Which of the following losses, in a synchronous motor, does not vary with load?

Answer/ Hint      

Answer : A

Explanation :

36.

The size of a synchronous motor decrease with the increase in

Answer/ Hint      

Answer : A

Explanation :

37.

Which of the following losses is not dissipated by the stator core surface in asynchronous motor?

Answer/ Hint      

Answer : D

Explanation :

38.

The duration of sudden short-circuit test on a synchronous motor is usually about

Answer/ Hint      

Answer : C

Explanation :

39.

The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as

Answer/ Hint      

Answer : B

Explanation :

40.

A synchronous machine with low value of short-circuit ratio has

Answer/ Hint      

Answer : A

Explanation :

41.

The construction of a synchronous motor resembles

Answer/ Hint      

Answer : C

Explanation :

42.

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will

Answer/ Hint      

Answer : A

Explanation :

43.

For power factor correction, synchronous motor operates at

Answer/ Hint      

Answer : A

Explanation :

44.

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency is known as

Answer/ Hint      

Answer : A

Explanation :

45.

Exciter of synchronous machine are

Answer/ Hint      

Answer : A

Explanation :

46.

The coupling angle or load angle of synchronous motor is defined as the angle between

Answer/ Hint      

Answer : B

Explanation :

47.

If the synchronous motor, properly synchronised of the supply is running on no load and is having negligible loss then

Answer/ Hint      

Answer : A

Explanation :

48.

The armature current of the synchronous motor

Answer/ Hint      

Answer : C

Explanation :

49.

The maximum power developed in a synchronous motor will depend on

Answer/ Hint      

Answer : D

Explanation :

50.

A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as

Answer/ Hint      

Answer : C

Explanation :

51.

In a synchronous motor, the break down torque is

Answer/ Hint      

Answer : A

Explanation :

52.

A synchronous motor can operate at

Answer/ Hint      

Answer : D

Explanation :

53.

At no-load, the armature current in a synchronous motor

Answer/ Hint      

Answer : C

Explanation :

54.

In asynchronous motor, the forced vibration will be maximum when driving

Answer/ Hint      

Answer : A

Explanation :

55.

The angle between the rotor poles and stator poles, in a synchronous motor is known as

Answer/ Hint      

Answer : B

Explanation :

56.

Higher the applied voltage ………will be the stator flux and …………will be the pull in torque

Answer/ Hint      

Answer : D

Explanation :

57.

In a synchronous machine in case the axis of field flux is in line with the armature flux, then

Answer/ Hint      

Answer : D

Explanation :

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Synchronous Motor MCQ Questions and Answers Page - 4