transformers MCQs – Page 2

Practise focused transformers questions with marked answers for exam preparation and subject revision.

transformers Mcqs
21. Natural oil cooling is used for transformers up to a rating of____________?
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A. 1000 kVA

B. 250 kVA

C. 3000 kVA

D. 500 kVA

22. A good voltage regulation of a transformer means________________?
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A. output voltage fluctuation from no load to full load is least

B. ood voltage regulation of a transformer means

C. difference between primary and secondary voltage is maximum

D. output voltage fluctuation with power factor is least

E. difference between primary and secondary voltage is least

23. The function of conservator in a transformer is___________________?
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A. to cool the transformer oil

B. to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings

C. to project againstinternal fault

D. to reduce copper as well as core losses

24. Power transformers are generally designed to have maximum efficiency around__________?
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A. half-load

B. 10% overload

C. near full-load

D. no-load

25. In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are______________?
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A. none of the above

B. copper losses

C. hysteresis and eddy current losses

D. friction and windage losses

26. In a power or distribution transformer about 10 per cent end turns are heavily insulated__________?
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A. to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns

B. none of the above

C. to reflect the line surge and save the winding of a transformer from damage

D. to absorb the line surge voltage and save the winding of transformer from damage

27. During open circuit test of a transformer:
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A. primary is supplied rated kVA

B. primary is supplied rated voltage

C. primary is supplied current at reduced voltage

D. primary is supplied full-load current

28. The path of the magnetic flux in transformer should have____________?
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A. high reluctance

B. high resistance

C. low reactance

D. low resistance

29. The voltage transformation ratio of a transformer is equal to the ratio of_______________?
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A. secondary terminal voltage to primary applied voltage

B. secondary induced e.m.f. to primary induced e.m.f

C. secondary current to primary current

D. primary turns to secondary turns

30. Reduction in core losses and increase in permeability are obtained with transformer employing__________?
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A. core built-up of laminations of cold rolled grain oriented steel

B. core built-up of laminations of hot rolled sheet

C. none of the above

D. either of the above

31. The main reason for generation of harmonics in a transformer could be_______________?
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A. poor insulation

B. fluctuating load

C. saturation of core

D. mechanical vibrations

32. Which of the following acts as a protection against high voltage surges due to lightning and switching ?
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A. Horn gaps

B. Thermal overload relays

C. Conservator

D. Breather

33. In the transformer the function of a conservator is to_______________?
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A. none of the above

B. provide fresh air for cooling the transformer

C. protect the transformer from damage when oil expends due to heating

D. supply cooling oil to transformer in time of need

34. The efficiency of a transformer, under heavy loads, is comparatively low because_______________?
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A. copper loss becomes high in proportion to the output

B. iron loss is increased considerably

C. voltage drop both in primary and secondary becomes large

D. secondary output is much less as compared to primary input

35. Star/star transformers work satisfactorily when________________?
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A. none of the above

B. load is balanced only

C. on balanced as well as unbalanced loads

D. load is unbalanced only

36. The use of higher flux density in the transformer design____________?
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A. reduces iron losses

B. reduces copper losses

C. reduces weight per kVA

D. increases part load efficiency

37. No-load current in a transformer________________?
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A. leads the voltage by about 75

B. leads the voltage by about 15

C. lags behind the voltage by about 15

D. lags behind the voltage by about 75
38. The purpose of providing iron core in a step-up transformer is?
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A. to provide coupling between primary and secondary

B. to decrease the magnitude of mag-netizing current

C. to increase the magnitude of mutual flux

D. to provide all above features
39. Which of the following is not a routine test on transformers ?
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A. Impedance test

B. Polarity test

C. Core insulation voltage test

D. Radio interference test
40. Hysteresis loss in a transformer varies as CBmax = maximum flux density) ?
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A. Bmax1-6

B. Bmax

C. Bmax1-83

D. B max