# Transformer MCQs Part 8

Transformer MCQs Part 8

## Eddy current losses in transformer are directly proportional to:

Eddy current losses in transformer are directly proportional to:

1. Supply frequency
2. Thickness of core lamination
3. Square of thickness of core lamination
4. Flex density in the core

Correct answer: 3. Square of thickness of core lamination

## Which of following is correct for a power transformer being operated at high frequencies:

Which of following is correct for a power transformer being operated at high frequencies:

1. Its primary will draw huge power
2. It will have excessive core losses
3. Its primary reactance will increase to very high value
4. None of these

Correct answer: 2. It will have excessive core losses

## Certain transformer has an efficiency of 80% and works at 100 V, 4 kW. If secondary voltage is 240 V, considering the power factor to be unit, what is value of primary current

Certain transformer has an efficiency of 80% and works at 100 V, 4 kW. If secondary voltage is 240 V, considering the power factor to be unit, what is value of primary current.

1. 10 A
2. 20 A
3. 30 A
4. 40 A

Explanation:

P = Vp * Ip * PF or Ip = P/(Vp * PF) = 4*1000/(100*1) = 40 A

## An isolation transformer has primary to secondary turns ratio of

An isolation transformer has primary to secondary turns ratio of:

1. 1:1
2. 1:2
3. 2:1
4. Any of above

Correct answer: 1. 1:1 Explanation: Isolation transformers are the ones that have a ratio of 1 to 1 between the primary and secondary windings. As the transformation ratio implies, the purpose of using this transformer is not to step up or step down, rather they are used to transfer electrical power from a source of alternating current (AC) power to some equipment or device while isolating the powered device from the power source, usually for safety reasons. Such transformers provide galvanic isolation, i.e no conductive path is present between source and load. This isolation is used to protect against electric shock and to suppress

## The voltage per turn of primary of transformer is _________ voltage per turn of its secondary

The voltage per turn of primary of transformer is _________ voltage per turn of its secondary:

1. Lesser than
2. Greater than
3. Equal to
4. None of these