Synchronous Generator MCQ Part 6

Damper windings are employed in alternator to

Damper windings are employed in alternator to:

1. Reduce windage losses
2. Parallel multiple alternators
3. Prevent hunting
4. Achieve synchronism
5. 2 & 4

Correct answer: 3. Prevent hunting

When the alternator operates at a load power factor of unity, the effect of armature reaction is

When the alternator operates at a load power factor of unity, the effect of armature reaction is:

1. Partially distorting
2. Wholly distorting
3. Wholly magnetizing
4. Partially magnetizing

Correct answer: 2. Wholly distorting

Explanation: When the alternator operates at a load power factor of unity, the effect of armature reaction is wholly distorting.

At unity power factor armature flux is in phase with induced EMF. For that instance the armature flux is in phase with induced EMF E. The field flux is in quadrature with E. As a result, the armature flux is in quadrature with main field field. Since the two fluxes are perpendicular to each other, at the unity power factor the armature reaction of alternators is wholly distorting.

The voltage regulation of alternator depends on which factor

The voltage regulation of alternator depends on which factor:

1. Load current
2. Power factor
3. Both of these
4. None of these

Correct answer: 3. Both of these

For which value of power factor the effect of armature reaction is minimum

For which value of power factor the effect of armature reaction is minimum:

1. 0.348
2. 0.5
3. 0.85
4. Unity

Correct answer: 4. Unity

For unity power factor the effect of armature reaction is minimum

MCQ#5

What happens to the power factor of an alternator operating in parallel with other alternators if its excitation is increased above the normal value of excitation:

1. The power factor becomes more leading
2. The power factor becomes more lagging
3. It remains same as before
4. It instantly leads but lags afterwards

Correct answer: 2. The power factor becomes more lagging