# Synchronous Generator MCQs Part 7

Synchronous Generator MCQs Part 7

## The stator of an alternator is identical to which of following machines

The stator of an alternator is identical to which of following machines:

1. DC Generator
2. 1-phase induction motor
3. 3-phase induction motor
4. 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:

1. Increases
2. Decreases
3. Remains constant
4. 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:

1. Non-sinusoidal
2. Truly sinusoidal
3. Free from harmonics
4. 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:

1. Windage losses
2. Operating speed
3. Generated voltage/phase
4. 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:

1. 2.5 Ω
2. 5 Ω
3. 7.5 Ω
4. 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