401. 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

402. 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

403. 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

404. Silicon steel used in lamination’s mainly reduces___________?
A. hysteresis loss
B. eddy current losses
C. copper losses
D. all of the above

405. Which winding of the transformer has less cross-sectional area?
A. Primary winding
B. Secondary winding
C. Low voltage winding
D. High voltage winding

406. Power transformers are generally designed to have maximum efficiency around__________?
A. no-load
B. half-load
C. near full-load
D. 10% overload

407. Which of the following is the main advantage of an auto-transformer over a two winding transformer?
A. Hysteresis losses are reduced
B. Saving in winding material
C. Copper losses are negligible
D. Eddy losses are totally eliminated

408. During short circuit test iron losses are negligible because of _____________?
A. the current on secondary side is negligible
B. the voltage on secondary side does not vary
C. the voltage applied on primary side is low
D. full-load current is not supplied to the transformer

409. Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________?
A. short-circuiting of the secondaries
B. power factor of one of the transformers is leading while that of the other lagging
C. transformers having higher copper losses will have negligible core losses
D. loading of the transformers not in proportion to their kVA ratings

410. 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

NOTE
IF YOU THINK ANY OF THE MCQ ABOVE IS WRONG.
PLEASE COMMENT WITH CORRECT ANSWER AND ITS DETAIL EXPLANATION IN COMMENT BOX.
THANK YOU