electrical

Alternator MCQ Questions and Answers Page - 2

1.

Distributed winding and short chording employed in ac machines will result in

Answer/ Hint      

Answer : D

Explanation :

2.

It is desirable to eliminate 5th harmonic voltage from the phase voltage of an alternator. The coils should be short-pitched by an electrical angle of

Answer/ Hint      

Answer : B

Explanation :

3.

The stator of a 3-phase, 6-pole ac machine has 45 slots. The stator winding has 45 coils with a coil span of 6 slots. What type of winding will be selected for this machine?

Answer/ Hint      

Answer : A

Explanation :

4.

The emf generated due to nth harmonic components of flux in an alternator will be _____the fundamental emf in magnitude

Answer/ Hint      

Answer : A

Explanation :

5.

4 pole star connected alternator running at 1500 rpm have 72 slots with 10 conductors per slot. The number of turns per phase and slot angle is

Answer/ Hint      

Answer : C

Explanation :

6.

Skew of rotor bar eliminates

Answer/ Hint      

Answer : A

Explanation :

7.

Harmonics in the emf generated in an alternator can be reduced by

Answer/ Hint      

Answer : D

Explanation :

8.

Chording and distribution of armature windings for ac machines results in

Answer/ Hint      

Answer : D

Explanation :

9.

The short pitch winding is preferred over full pitch winding for an alternator because it

Answer/ Hint      

Answer : D

Explanation :

10.

The aircraft alternators are designed  to generate emf of high frequency of 400 Hz in order to

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

11.

Armature winding is one in which

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

12.

Armature winding in ac machines

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

13.

The stator of modern alternators are wound for _____phase groups

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

14.

Concentrated winding has

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

15.

For a two layer winding the number of stator slots is equal to the number of

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

16.

for a concentrated winding  the polar group of each phase is ____electrical degrees part

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

17.

Distributed winding is preferred over concentrated winding as it

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

18.

In a synchronous alternator, which of the following coils will have emf closer to sine wave form

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

19.

If the space flux distribution is non sinusoidal , emf induced in the distributed winding will be

Answer/ Hint      

Answer : Select Correct Ans

Explanation :

20.

In a synchronous generator, a divided winding is preferable to a conventional winding rotor because of

Answer/ Hint      

Answer : B

Explanation :

21.

A 4-pole 3 phase, double layer winding is housed in a 36-slot stator for a ac machine with 600 phase spread. Coil span is 7 slot pitches. Number of slots in which top and bottom layers belong to different phases is

Answer/ Hint      

Answer : A

Explanation :

22.

In a cylindrical rotor synchronous machine, the phasor addition of stator and rotor mmfs is possible because

Answer/ Hint      

Answer : C

Explanation :

23.

Three phase alternators are invariably connected in star so as to

Answer/ Hint      

Answer : B

Explanation :

24.

The stator winding of an alternator is normally connected in star to eliminate the _____harmonic component of the voltage wave from

Answer/ Hint      

Answer : A

Explanation :

25.

If the dimensions of all of the parts of a synchronous generator and the number of field and armature turns are doubled, then the generated voltage will change by a factor of

Answer/ Hint      

Answer : C

Explanation :

26.

The angle between induced emf and terminal voltage on no load for a single-phase alternator is

Answer/ Hint      

Answer : C

Explanation :

27.

The 5th space harmonics in the mmf developed by balanced fundamental frequency armature currents rotate at _____times the synchronous speed with respect to the field

Answer/ Hint      

Answer : B

Explanation :

28.

When a three-phase alternator supplies capacitive load, armature reaction flux will be

Answer/ Hint      

Answer : B

Explanation :

29.

Fleming’s left-hand rule may be applied to an electric generator to find out direction of

Answer/ Hint      

Answer : B

Explanation :

30.

In an alternator, the armature reaction will be completely magnetizing case the load power factor is

Answer/ Hint      

Answer : B

Explanation :

31.

The dark and bright lamp method is used for

Answer/ Hint      

Answer : B

Explanation :

32.

In a synchronous machine, all of the following losses are fixed except

Answer/ Hint      

Answer : B

Explanation :

33.

In a star connected armature winding

Answer/ Hint      

Answer : A

Explanation :

34.

When the speed of an alternator increases

Answer/ Hint      

Answer : B

Explanation :

35.

The slip rings employed in a 3-phase alternator in hydro station are insulated for

Answer/ Hint      

Answer : A

Explanation :

36.

An alternator is capable of delivering power at a particular efficiency. The frequency can be increased by

Answer/ Hint      

Answer : D

Explanation :

37.

In alternators the standard practice, now-a days is to have

Answer/ Hint      

Answer : A

Explanation :

38.

In an alternator, for a coil having a span of 2/3 of pole pitch, the coil span factor will be

Answer/ Hint      

Answer : A

Explanation :

39.

Excessive windage loss and noise occur with

Answer/ Hint      

Answer : B

Explanation :

40.

Regulation of an alternator supplying leading load is

Answer/ Hint      

Answer : C

Explanation :

41.

An infinite bus bar has

Answer/ Hint      

Answer : A

Explanation :

42.

Which harmonic will be totally eliminated in an alternator by using a fractional pitch of 4/5?

Answer/ Hint      

Answer : B

Explanation :

43.

Dirt accumulation in generator can cause all of the following except

Answer/ Hint      

Answer : A

Explanation :

44.

If an alternator is operating at leading power factor, then it can be concluded that

Answer/ Hint      

Answer : B

Explanation :

45.

Which fractional pitch will eliminate the seventh harmonic from the voltage waveform of an alternator?

Answer/ Hint      

Answer : A

Explanation :

46.

Damper winding on alternator results in all of the following except

Answer/ Hint      

Answer : A

Explanation :

47.

In a cylindrical rotor how much portion of the rotor is wound?

Answer/ Hint      

Answer : C

Explanation :

48.

The speed of an alternator is changed from 3000 r.p.m to 1500 r.p.m. the generated e.m.f /phase will become

Answer/ Hint      

Answer : B

Explanation :

49.

Zero power factor method for an alternator is generally used to determine

Answer/ Hint      

Answer : C

Explanation :

50.

In an alternator the armature reaction is mainly influenced by

Answer/ Hint      

Answer : A

Explanation :

51.

Regulation of an alternator supplying resistive or inductive load is

Answer/ Hint      

Answer : B

Explanation :

52.

4 pole 1500 r.p.m alternator will generate e.m.f at

Answer/ Hint      

Answer : C

Explanation :

53.

To obtain sinusoidal flux distribution

Answer/ Hint      

Answer : B

Explanation :

54.

In air-crafts, alternators have operating frequency of

Answer/ Hint      

Answer : B

Explanation :

55.

Alternators, now a days are designed to have poor regulation because

Answer/ Hint      

Answer : B

Explanation :

56.

Voltage regulation of an alternator is usually

Answer/ Hint      

Answer : C

Explanation :

57.

In an alternator, the stator frame serves

Answer/ Hint      

Answer : D

Explanation :

58.

For a given output steam turbo-alternator are much smaller is size than water turbine-alternators because

Answer/ Hint      

Answer : C

Explanation :

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