A shunt generator has a critical field resistance of 200 ohms at a speed of 800 rpm. If the speed of the generator is increased to 1000 rpm. What is the change in critical field resistance of the generator

1.  Decrease to 160 ohm
2. Remains the same at 200 ohm
3. Increase to 250 ohm
4. Increase to 312.5 ohm

Answer: Increase to 250 ohm

The use of higher flux density in the transformer design

1. decrease the total weight/KVA
2. increase the total weight/KVA
3. decrease the weight of iron/KVA but increase that of copper
4. decrease the weight of copper/KVA but increase that of iron.

Answer :  decrease the total weight/KVA

In a scott connected transformer the number of primary and teaser turns respectively are

1. N, 2/SQRT(3) N
2. N/2,N
3. SQRT (3) N/2,N
4. N, SQRT (3) N/2

Answer :   N, SQRT (3) N/2

On the two side of star/delta transformers

1. Voltage and current are both in phase
2. the voltage and current both differ in phase by 30 degree.
3. the voltage differ in phase by 30 degree but currents are in phase.
4. the current differ in phase by 30 degree but voltages are in phase.

Answer : the voltage and current both differ in phase by 30 degree.

A transformer on no load is switched on to a source of voltage. it will a current

1. which is same as the steady state magnetizing current.
2. which is several times the steady state magnetizing current , depending upon the initial state of the residual flux in the transformer core.
3. which is several times the steady state magnetizing current , independent of the initial state of the residual flux in the transformer core.
4. which is twice the steady state magnetizing current provided the core has no residual flux.

Answer: 

which is several times the steady state magnetizing current , depending upon the initial state of the residual flux in the transformer core.

As compared to delta-delta bank, the capacity of the V-V bank of transformers is .....percent.

1. 57.7
2. 66.7
3. 50
4. 86.6

Answer: 

1. 57.7

Why are transformer stamping annealed before being used for the building?

1. To reduce eddy current loss due to burning of edges
2.  To reduce hysteresis loss due to burning of edges
3. To give mechanical strength to the core
4. To increase core permeability

Answer : 

1. To reduce eddy current loss due to burning of edges