electrical

Alternator MCQ Questions and Answers Page - 3

1.

The seventh space harmonics in the mmf produced by balanced fundamental frequency armature currents rotate at ____times the synchronous speed with respect to the field

Answer/ Hint      

Answer : C

Explanation :

2.

The phase sequence of a three-phase alternator will reverse if

Answer/ Hint      

Answer : B

Explanation :

3.

Power factor of an alternator driven by constant prime mover input can be changed by changing its

Answer/ Hint      

Answer : C

Explanation :

4.

How can the reactive power delivered by a synchronous generator be controlled?

Answer/ Hint      

Answer : B

Explanation :

5.

The rating of the prime mover driving an alternator is determined entirely by its ____rating

Answer/ Hint      

Answer : C

Explanation :

6.

When an alternator designed for operation at 60 Hz is operated at 50 Hz

Answer/ Hint      

Answer : B

Explanation :

7.

The rating of a synchronous machine is usually governed by its

Answer/ Hint      

Answer : B

Explanation :

8.

The flux set up by the armature current, which does not cross the air gap and takes a different path is called the ____flux

Answer/ Hint      

Answer : A

Explanation :

9.

The magnitude of leakage flux depends on

Answer/ Hint      

Answer : D

Explanation :

10.

Leakage reactance of the armature of a salient pole synchronous machine which varies with the position of rotor is due to leakage flux

Answer/ Hint      

Answer : B

Explanation :

11.

In a synchronous generator

Answer/ Hint      

Answer : C

Explanation :

12.

Armature reaction effect is / are ____on the main field flux

Answer/ Hint      

Answer : A

Explanation :

13.

The armature reaction effect in a synchronous machine depends on

Answer/ Hint      

Answer : D

Explanation :

14.

In a synchronous generator, the effect of cross magnetization is to make the generated voltage

Answer/ Hint      

Answer : B

Explanation :

15.

In an alternator, the armature mmf will be in phase with the main field flux only when the load is purely

Answer/ Hint      

Answer : C

Explanation :

16.

In an alternator, the armature reaction is considered to be equivalent to a fictitious

Answer/ Hint      

Answer : A

Explanation :

17.

A synchronous generator is feeding a zero-power factor (lagging) load at rated current. The armature reaction is

Answer/ Hint      

Answer : B

Explanation :

18.

Armature reaction AT of a synchronous generator supplying power at rated voltage with zero power factor lagging is

Answer/ Hint      

Answer : B

Explanation :

19.

The synchronous reactance is the

Answer/ Hint      

Answer : C

Explanation :

20.

Drop in terminal voltage of an alternator due to armature reaction is countered by

Answer/ Hint      

Answer : D

Explanation :

21.

The saturated synchronous reactance of an alternator is _____its unsaturated synchronous reactance

Answer/ Hint      

Answer : B

Explanation :

22.

In an alternator, short circuit current is limited by

Answer/ Hint      

Answer : B

Explanation :

23.

When the load (inductive) is thrown off, the terminal voltage will

Answer/ Hint      

Answer : A

Explanation :

24.

As the leading power factor of the load of an alternator decreases, the magnitude of generated voltage required to give rated terminal voltage

Answer/ Hint      

Answer : B

Explanation :

25.

 In a synchronous generator delivering lagging power factor load

Answer/ Hint      

Answer : A

Explanation :

26.

The power factor on which an alternator operates depends on the

Answer/ Hint      

Answer : B

Explanation :

27.

Unbalanced 3-phase stator currents cause

Answer/ Hint      

Answer : D

Explanation :

28.

Regulation of an alternator supplying resistive or inductive load is

Answer/ Hint      

Answer : A

Explanation :

29.

Alternators of a central power station will have

Answer/ Hint      

Answer : A

Explanation :

30.

Non-salient pole type of rotor construction is usually provided in the alternators used in

Answer/ Hint      

Answer : B

Explanation :

31.

In an alternator terminal voltage rise will be more

Answer/ Hint      

Answer : B

Explanation :

32.

Turbo-alternator usually have

Answer/ Hint      

Answer : D

Explanation :

33.

In an alternator short pitch coils are used

Answer/ Hint      

Answer : D

Explanation :

34.

If the input prime mover of an alternator is kept constant but the excitation is increased then

Answer/ Hint      

Answer : A

Explanation :

35.

Generated e.m.f for same field current and double speed will be

Answer/ Hint      

Answer : B

Explanation :

36.

If the space flux distribution is non-sinusoidal e.m.f induced in the distributed winding

Answer/ Hint      

Answer : B

Explanation :

37.

Voltage regulation obtained by synchronous impedance method is

Answer/ Hint      

Answer : C

Explanation :

38.

In an alternator short-circuit current is limited by

Answer/ Hint      

Answer : B

Explanation :

39.

In an alternator, armature reaction is considered equivalent to

Answer/ Hint      

Answer : C

Explanation :

40.

Synchronous impedance method gives more regulation as compared to ampere turn method because

Answer/ Hint      

Answer : A

Explanation :

41.

Leakage reactance of the armature of a salient pole synchronous machine which varies with the position of the rotor is due to

Answer/ Hint      

Answer : C

Explanation :

42.

Turbo-rotor is made up of

Answer/ Hint      

Answer : A

Explanation :

43.

A commercials alternator has

Answer/ Hint      

Answer : A

Explanation :

44.

For the alternators operating in parallel, if the load shared by one of them is to be increased, its field excitation is

Answer/ Hint      

Answer : C

Explanation :

45.

Which of the following methods is best for finding the voltage regulation?

Answer/ Hint      

Answer : C

Explanation :

46.

For a 3-phase winding with 5 slots per pole per phase and with coil span of 12 slot pitch, the value of pitch factor is

Answer/ Hint      

Answer : B

Explanation :

47.

Salient pole rotors are used where

Answer/ Hint      

Answer : C

Explanation :

48.

The power factor of an alternator is determined by its

Answer/ Hint      

Answer : D

Explanation :

49.

If the input to the prime-mover of an alternator is kept constant but excitations changed then

Answer/ Hint      

Answer : B

Explanation :

50.

For parallel operation, A.C polyphase alternators must have the same

Answer/ Hint      

Answer : D

Explanation :

51.

Unlike D.C generator kW rating, alternator are rated in

Answer/ Hint      

Answer : D

Explanation :

52.

Dirt accumulation in generator can cause

Answer/ Hint      

Answer : D

Explanation :

53.

An alternator running in parallel with other alternators all having automatic voltage regulators is to be taken off the bus. The usual procedure before opening the switch is to

Answer/ Hint      

Answer : A

Explanation :

54.

Due to which of the following reasons concentrated windings are not used in alternators?

Answer/ Hint      

Answer : D

Explanation :

55.

A stationary alternator should not be connected to alive bus bar because it

Answer/ Hint      

Answer : A

Explanation :

56.

The power drawn by the prime-mover of an alternator, under no-load condition, goes to

Answer/ Hint      

Answer : C

Explanation :

57.

In a large generator, damper

Answer/ Hint      

Answer : B

Explanation :

58.

The choice of field construction, in an alternator is basically determined by

Answer/ Hint      

Answer : D

Explanation :

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