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MCQs 1: Which of the following does not change in an ordinary transformer ?

Frequency Voltage Current Any of the above
Answer Explanation

MCQs 2: The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer?

Conservator Breather Bushings Buchholz relay
Answer Explanation

MCQs 3: The magnetising current of a transformer is usually small because it has___________?

small air gap large leakage flux laminated silicon steel core fewer rotating parts
Answer Explanation

MCQs 4: Buchholz’s relay gives warning and protection against_________________?

electrical fault inside the transformer itself electrical fault outside the transformer in outgoing feeder for both outside and inside faults none of the above
Answer Explanation

MCQs 5: Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________?

short-circuiting of the secondaries power factor of one of the transformers is leading while that of the other lagging transformers having higher copper losses will have negligible core losses loading of the transformers not in proportion to their kVA ratings
Answer Explanation

MCQs 6: During short circuit test iron losses are negligible because of _____________?

the current on secondary side is negligible the voltage on secondary side does not vary the voltage applied on primary side is low full-load current is not supplied to the transformer
Answer Explanation

MCQs 7: Which of the following is the main advantage of an auto-transformer over a two winding transformer?

Hysteresis losses are reduced Saving in winding material Copper losses are negligible Eddy losses are totally eliminated
Answer Explanation

MCQs 8: Power transformers are generally designed to have maximum efficiency around__________?

no-load half-load near full-load 10% overload
Answer Explanation

MCQs 9: Which winding of the transformer has less cross-sectional area?

Primary winding Secondary winding Low voltage winding High voltage winding
Answer Explanation

MCQs 10: Silicon steel used in lamination’s mainly reduces___________?

hysteresis loss eddy current losses copper losses all of the above
Answer Explanation

MCQs 11: Delta/star transformer works satisfactorily when______________?

load is balanced only load is unbalanced only on balanced as well as unbalanced loads none of the above
Answer Explanation

MCQs 12: Star/star transformers work satisfactorily when________________?

load is unbalanced only load is balanced only on balanced as well as unbalanced loads none of the above
Answer Explanation

MCQs 13: Which of the following property is not necessarily desirable in the material for transformer core ?

Mechanical strength Low hysteresis loss High thermal conductivity High permeability
Answer Explanation

MCQs 14: Distribution transformers are generally designed for maximum efficiency around________________?

90% load zero load 25% load 50% load
Answer Explanation

MCQs 15: The value of flux involved m the e.m.f. equation of a transformer is____________?

average value r.m.s. value maximum value instantaneous value
Answer Explanation

MCQs 16: The main reason for generation of harmonics in a transformer could be_______________?

fluctuating load poor insulation mechanical vibrations saturation of core
Answer Explanation

MCQs 17: Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds?

50°C 80°C 100°C 150°C
Answer Explanation

MCQs 18: The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be___________?

6400 W 1600 W 800 W 400 W
Answer Explanation

MCQs 19: A Buchholz relay can be installed on______________?

auto-transformers air-cooled transformers welding transformers oil cooled transformers
Answer Explanation

MCQs 20: A transformer oil must be free from________________?

sludge odour gases moisture
Answer Explanation

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