# Transformer MCQs Part 16

Transformer MCQs Part 16

## At full-load certain transformer has 400 W iron loss. The iron loss at half-full load will have value

At full-load certain transformer has 400 W iron loss. The iron loss at half-full load will have value:

1. 50 W
2. 100 W
3. 200 W
4. 400 W

Explanation: Iron losses are independent of load and depend on supply voltage, frequency. Therefore the iron losses at half-full load will be same as they are on full-load.

## The primary leakage flux in a transformer links

The primary leakage flux in a transformer links:

1. Primary winding only
2. Secondary winding only
3. Both of these
4. None of these

Correct answer: 1. Primary winding only

## A 30 turn iron-cored inductor is connected to a 60 Hz, 110 V source. The maximum flux density in core is 1.2 Wb/m^2. The cross-sectional area of the core is

A 30 turn iron-cored inductor is connected to a 60 Hz, 110 V source. The maximum flux density in core is 1.2 Wb/m^2. The cross-sectional area of the core is:

1. 0.01102 m^2
2. 0.01135 m^2
3. 0.01146 m^2
4. 0.01165 m^2

Formula for area is: a = Φm/Bm

From formula: E = 4.44 * f *   Ns * Φm

110 = 4.44 * 60 * 30 * Φm

Or Φm = 0.01376

As mentioned in start a = Φm/Bm = 0.01376/1.2 Wb/m2 = 0.01146 m^2

## Open-circuit test on transformer is done on

Open-circuit test on transformer is done on:

1. Low voltage winding
2. High voltage winding
3. Any of above
4. None of above

Correct answer: 1. Low voltage winding

Explanation: Open circuit test on transformer is carried out on low voltage winding (High voltage winding is left open). Although the iron losses on either of the windings will be same, but open circuit test is carried out on low voltage winding since, measurement on high voltage winding will have very small no-load current and very high voltage.

## Which of following connection of transformer will give the highest secondary voltage

Which of following connection of transformer will give the highest secondary voltage:

1. Delta primary, Star secondary
2. Delta primary, Delta secondary
3. Star primary, Star secondary
4. Star primary, Delta secondary

Correct answer: 1. Delta primary, Star secondary