Transformer MCQ Part 22

Contents

- 1 At very low frequencies transformer operates poorly, since
- 2 The primary and secondary winding of transformers are wound on top of each other in order to reduce
- 3 In case of practical transformers, the copper losses account for what percentage of total losses
- 4 The iron losses and full load Cu losses in a 20 kVA transformer are 400 and 1600 W respectively. What is value of load at which maximum efficiency occurs
- 5 The winding of transformer with greater number of turns will be

## At very low frequencies transformer operates poorly, since

At very low frequencies transformer operates poorly, since:

- Primary reactance is very high
- Permeability of core is increased
- Magnetizing current is abnormally high
- None of these

Correct answer: 3. Magnetizing current is abnormally high

## The primary and secondary winding of transformers are wound on top of each other in order to reduce

The primary and secondary winding of transformers are wound on top of each other in order to reduce:

- Iron losses
- Copper losses
- Eddy current losses
- Leakage reactance

Correct answer: 4. Leakage reactance

## In case of practical transformers, the copper losses account for what percentage of total losses

In case of practical transformers, the copper losses account for what percentage of total losses:

- 25%
- 50%
- 85%
- 99.9%

Correct answer: 3. 85%

## The iron losses and full load Cu losses in a 20 kVA transformer are 400 and 1600 W respectively. What is value of load at which maximum efficiency occurs

The iron losses and full load Cu losses in a 20 kVA transformer are 400 and 1600 W respectively. What is value of load at which maximum efficiency occurs:

- 10 kVA
- 20 kVA
- 30 kVA
- 40 kVA

Correct answer: 1. 10 kVA

Solution:

Load for max efficiency = F.L kVA * √(Iron loss/F.L Cu losses)

———————————-

Load for max efficiency = 20 * √400/1600 = 10 kVA

## The winding of transformer with greater number of turns will be

The winding of transformer with greater number of turns will be:

- Low voltage winding
- High voltage winding
- Either of above
- None of above

Correct answer: 2. High voltage winding