# Synchronous Generator MCQs Part 6

Synchronous Generator MCQs Part 6

## If number of poles of alternator is increased, the generated EMF

If number of poles of alternator is increased, the generated EMF:

1. Increases
2. Decreases
3. Remains constant
4. None of these

Correct answer: 1. Increases

Explanation:

EMF generated per phase E = 2.22 fZΦ

f = NP/120

## The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for which of following machines

The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for which of following machines:

1. A DC machine
2. An induction machine
3. A synchronous machine
4. All the above machines

Correct answer: 3. A synchronous machine

## In order to produce an EMF of given frequency, an alternator will run at greatest speed for what number of poles

In order to produce an EMF of given frequency, an alternator will run at greatest speed for what number of poles:

1. 2
2. 4
3. 8
4. 12

Correct answer: 1. 2

## In armature winding of an alternator, the coil span falls short of full-pitch by 60° (electrical). The pitch factor will be

In armature winding of an alternator, the coil span falls short of full-pitch by 60° (electrical). The pitch factor will be:

1. 0.25
2. 0.5
3. 0.866
4. None of these

Correct answer: 3. 0.866

Explanation: Pitch factor (Kp) = cos (α/2) = cos(60°/2) = 0.866

## The synchronous reactance of alternator ___________ as the iron is saturated

The synchronous reactance of alternator ___________ as the iron is saturated:

1. Increases
2. Decreases
3. Remains unchanged
4. None of the above

Correct answer: 2. Decreases