# Synchronous Generator MCQs Part 13

Synchronous Generator MCQs Part 13

## An under-excited alternator supplies which type of power

An under-excited alternator supplies which type of power:

1. Lagging VAR
3. No reactive power
4. None of the above

## The angular velocity of two-pole alternator running at 2000 RPM is

The angular velocity of two-pole alternator running at 2000 RPM is

1. 167 Hz
2. 189 Hz
3. 209 Hz
4. 242 Hz

Explanation:

Angular velcoty (ω) = 2πN/60 = (2π*2000)/60 = 209.44 = 209 rad/s

## The infinite busbar has

The infinite busbar has:

1. constant frequency
2. constant voltage
3. Both of these
4. None of these

Correct answer: 3. Both of these

Explanation: An infinite busbar has a fixed voltage and fixed frequency. The voltage and frequency are constant even after a variation in the load. Alternators operating in parallel is an example of an infinite busbar.

The infinite bus imposes its voltage and frequency on alternators connected to its terminal. If an alternator goes on or off the overall system continues to work in the same manner.

## The output frequency of the synchronous generator depends on

The output frequency of the synchronous generator/alternator depends on

1. Rotational speed
2. Pole number
3. Both of these
4. None of these

Correct answer: 3. Both of these

Explanation: The output frequency of the alternator can be expressed mathematically by the formula:

f = P x N / 120

The output frequency of the alternator is dependent on both pole number as well as the rotational speed of the alternator.

## Alternators driven by XYZ do not have a tendency to hunt. Here XYZ implies

Alternators driven by XYZ do not have a tendency to hunt. Here XYZ implies:

1. Diesel engines
2. Steam turbines
3. Water turbines
4. None of the above