# Synchronous Generator MCQs Part 14

Synchronous Generator MCQs Part 14

## Armature windings of an alternator are generally

Armature windings of an alternator are generally

1. Open windings
2. Closed windings
3. Partly open and partly closed windings
4. None of the above

## If the excitation to an alternator connected to an infinite busbar is changed

If the excitation to an alternator connected to an infinite busbar is changed while keeping the power input to its prime-mover unchanged, then which of following is correct:

1. Kva output will change
2. Kvar output will change
3. Power factor will change
4. All of these

Correct answer: 4. All of these

## The voltage regulation of an alternator for PF of 0.8 lagging is X at unity PF

The voltage regulation of an alternator for PF of 0.8 lagging is X at unity PF:

1. Smaller than
2. Greater than
3. The same as
4. None of the above

## The voltage regulation of an alternator supplying power to a load with a leading power factor always is

The voltage regulation of an alternator supplying power to a load with a leading power factor always is:

1. Zero
2. Positive
3. Negative
4. Unity

## A 3 phase, 32 pole alternator has star-connected winding having 120 slots

A 3 phase, 32 pole alternator has star-connected winding having 120 slots and 10 conductors per slot. The flux per is 30 mWb that is sinusoidally distributed and the speed is 375 RPM. The line EMF is:

1. 1538 Hz
2. 2307 Hz
3. 3076 Hz
4. 4614 Hz

Explanation:

Line EMF = √3 * Generated EMF per phase

Generated EMF per phase = 2.22 fZΦ = 2.22

Where Z = No of conductors per phase = No of slots per phase * No of conductors per slot

Number of slots per phase = 120/3 = 40

Number of conductors per phase (Z) = 40 * 10 = 400

Formula for frequency (f) = NP/120 = (375 * 32)/120 = 100 Hz

————

Now Generated EMF per phase = 2.22 fZΦ = 2.22 * 100 * 400 * 30 * 10^-3 = 2664 V

————

Line EMF = √3 * Generated EMF per phase = √3 * 2664 = 4614 V