Synchronous Generator MCQs Part 6
Contents
- 1 If number of poles of alternator is increased, the generated EMF
- 2 The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for which of following machines
- 3 In order to produce an EMF of given frequency, an alternator will run at greatest speed for what number of poles
- 4 In armature winding of an alternator, the coil span falls short of full-pitch by 60° (electrical). The pitch factor will be
- 5 The synchronous reactance of alternator ___________ as the iron is saturated
If number of poles of alternator is increased, the generated EMF
If number of poles of alternator is increased, the generated EMF:
- Increases
- Decreases
- Remains constant
- 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:
- A DC machine
- An induction machine
- A synchronous machine
- 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:
- 2
- 4
- 8
- 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:
- 0.25
- 0.5
- 0.866
- 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:
- Increases
- Decreases
- Remains unchanged
- None of the above
Correct answer: 2. Decreases