Transformers

Which of the following is not a part of transformer installation ?

A. Conservator
B. Breather
C. Buchholz relay
D. Exciter

The purpose of providing an iron core in a transformer is to_____________?

A. provide support to windings
B. reduce hysteresis loss
C. decrease the reluctance of the magnetic path
D. reduce eddy current losses

No-load current in a transformer________________?

A. lags behind the voltage by about 75°
B. leads the voltage by about 75°
C. lags behind the voltage by about 15°
D. leads the voltage by about 15°

The efficiency of a transformer will be maximum when_____________?

A. copper losses = hysteresis losses
B. hysteresis losses = eddy current losses
C. eddy current losses = copper losses
D. copper losses = iron losses

The permissible flux density in case of cold rolled grain oriented steel is around__________?

A. 1.7 Wb/m2
B. 2.7 Wb/m2
C. 3.7 Wb/m2
D. 4.7 Wb/m2

Sumpner’s test is conducted on transformers to determine_____________?

A. temperature
B. stray losses
C. all-day efficiency
D. none of the above

The dielectric strength of transformer oil is expected to be______________?

A. lkV
B. 33 kV
C. 100 kV
D. 330 kV

No-load on a transformer is carried out to determine______________?

A. copper loss
B. magnetising current
C. magnetising current and loss
D. efficiency of the transformer

A. high resistance
B. high reluctance
C. low resistance
D. low reluctance

The no-load current drawn by transformer is usually what per cent of the full-load current ?

A. 0.2 to 0.5 per cent
B. 2 to 5 per cent
C. 12 to 15 per cent
D. 20 to 30 per cent