# Transformer MCQs Part 17

Transformer MCQs Part 17

## Assuming a maximum flux density of 1.3 Wb/m^2 and induced voltage per turn of 40 V, the core area required for 1600 kVA, 5500/220 V, 60 Hz single phase core type power transformer is:

Assuming a maximum flux density of 1.3 Wb/m^2 and induced voltage per turn of 40 V, the core area required for 1600 kVA, 5500/220 V, 60 Hz single phase core type power transformer is:

1. 1025 cm^2
2. 1100 cm^2
3. 1155 cm^2
4. 1200 cm^2

From formula: E = 4.44 * f *   N * Φm

E/N = 4.44 * f *  Φm

40 = 4.44 * 60 *  Φm

Φm = 0.15015 Wb

Formula for area is: a = Φm/Bm

a = 0.1501/1.3 = 0.1155 m^2 = 1155 cm^2

## A transformer has full load copper losses of 400 W. The copper loss at half of full-load will be

A transformer has full load copper losses of 400 W. The copper loss at half of full-load will be:

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

Soution:

Copper losses vary as square of current

At half-full load = (1/2)^2 * Full load Cu loss = ¼ * 400 = 100 W

## Short circuit test helps us to determine

Short circuit test helps us to determine:

1. Iron losses at no load
2. Cu losses at no load
3. Both of these
4. None of these

Correct answer: 2. Cu losses at no laod

## If there is break in 220/110 V autotransformer in winding that is common to both HV and LV sides, then the output voltage on LV side will be:

If there is break in 220/110 V autotransformer in winding that is common to both HV and LV sides, then the output voltage on LV side will be:

1. 110 V
2. 220 V
3. Zero
4. None of these