# Transformer MCQs Part 4

Transformer MCQs Part 4

## A 3000/150 V, 30 kVA transformer has 50 turns in secondary. What is full load primary current of transformer

A 3000/150 V, 30 kVA transformer has 50 turns in secondary. What is full load primary current of the transformer:

1. 1 A
2. 2 A
3. 5 A
4. 10 A

Correct answer: 4. 10 A

Solution: I = kVA/Primary Voltage = 30*1000/3000 = 10 A

## If primary of transformer is connected to dc power supply, the

If primary of transformer is connected to dc power supply, then:

1. Primary leakage reactance will increase
2. Primary draws little to none amount of current
3. Primary might burn
4. Core losses are increased

Correct answer: 3. Primary might burn

Explanation:

When dc supply is provided to a transformer it produces steady flux, as a result of this no emf is induced in primary of transformer. The primary winding draws large amount of current due to its small resistance (Ohm’s law: Current is inversely proportional to resistance). The large current might burn out the primary of transformer.

## A transformer doesn’t possess changing property for

A transformer doesn’t possess changing property for:

1. Voltage
2. Current
3. Power
4. Impedance

Correct answer: 3. Power

## The transformer that has no electric isolation

The transformer that has no electric isolation:

1. Potential transformer
2. Current transformer
3. Power transformer
4. Autotransformer

Correct answer: 4. Autotransformer

Explanation: The autotransformer is an electrical transformer with only one winding. In an autotransformer, portions of the same winding act as both the primary winding and secondary winding sides of the transformer, due to which there is no electric isolation between primary and secondary circuits.

## Iron core is provided in transformer so as to

Iron core is provided in transformer so as to:

1. Reduce core losses
2. Increase its weight
3. Provide tight magnetic coupling
4. None of these

Correct answer: 3. Provide tight magnetic coupling

Explanation: Iron core in transformer ensures that tight magnetic coupling is present between two windings. In case of practical transformer, the coefficient of coupling can be as high as 0.99