Synchronous Generator MCQs Part 7
Contents
- 1 The stator of an alternator is identical to which of following machines
- 2 With the size of the machine, the full-load efficiency of alternator
- 3 Effect of cross magnetization in synchronous generator makes it voltage
- 4 In an alternator, the armature reaction influences which of following
- 5 A 3 phase synchronous generator generates an open circuit phase voltage of 2000 V when the exciting current is 50 A
The stator of an alternator is identical to which of following machines
The stator of an alternator is identical to which of following machines:
- DC Generator
- 1-phase induction motor
- 3-phase induction motor
- Rosenberg generator
Correct answer: 3. 3-phase induction motor
With the size of the machine, the full-load efficiency of alternator
With the size of the machine, the full-load efficiency of alternator:
- Increases
- Decreases
- Remains constant
- None of these
Correct answer: 1. Increases
Effect of cross magnetization in synchronous generator makes it voltage
Effect of cross magnetization in synchronous generator makes it voltage:
- Non-sinusoidal
- Truly sinusoidal
- Free from harmonics
- None of these
Correct answer: 1. Non-sinusoidal
In an alternator, the armature reaction influences which of following
In an alternator, the armature reaction influences which of following:
- Windage losses
- Operating speed
- Generated voltage/phase
- None of the above
Correct answer: 3. Generated voltage/phase
A 3 phase synchronous generator generates an open circuit phase voltage of 2000 V when the exciting current is 50 A
A 3 phase synchronous generator generates an open circuit phase voltage of 2000 V when the exciting current is 50 A. The short circuit current for same excitation being 400 A. The value of synchronous reactance per phase is:
- 2.5 Ω
- 5 Ω
- 7.5 Ω
- 12.5 Ω
Correct answer: 2. 5 Ω
Explanation:
Synchronous reactance (Xs) = Eph/Isc = 2000/400 = 5 Ω
Where in the formula
Eph = Rated open circuit phase voltage
Isc = Short circuit current per phase using same exciting current that was required to produce Eph