Which of the following does not change in an ordinary transformer ?

A. Frequency
B. Voltage
C. Current
D. Any of the above

The magnetising current of a transformer is usually small because it has___________?

A. Small air gap
B. Large leakage flux
C. Laminated silicon steel core
D. Fewer rotating parts

Buchholz’s relay gives warning and protection against_________________?

A. Electrical fault inside the transformer itself
B. Electrical fault outside the transformer in outgoing feeder
C. For both outside and inside faults
D. None of the above

Delta/star transformer works satisfactorily when______________?

A. Load is balanced only
B. Load is unbalanced only
C. On balanced as well as unbalanced loads
D. None of the above

Star/star transformers work satisfactorily when________________?

A. Load is unbalanced only
B. Load is balanced only
C. On balanced as well as unbalanced loads
D. None of the above

Which of the following property is not necessarily desirable in the material for transformer core ?

A. Mechanical strength
B. Low hysteresis loss
C. High thermal conductivity
D. High permeability

Distribution transformers are generally designed for maximum efficiency around________________?

A. 90% load
B. Zero load
C. 25% load
D. 50% load

The main reason for generation of harmonics in a transformer could be_______________?

A. Fluctuating load
B. Poor insulation
C. Mechanical vibrations
D. Saturation of core

Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds?

A. 50°c
B. 80°c
C. 100°c
D. 150°c

A Buchholz relay can be installed on______________?

A. Oil cooled transformers
B. Auto-transformers
C. Air-cooled transformers
D. Welding transformers