Transformers

41. The power transformer is a constant

voltage device
current device
power device
main flux device

Detailed SolutionThe power transformer is a constant

42. 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

Detailed SolutionThe value of flux involved m the e.m.f. equation of a transformer is

43. Natural oil cooling is used for transformers up to a rating of

3000 kVA
1000 kVA
500 kVA
250 kVA

Detailed SolutionNatural oil cooling is used for transformers up to a rating of

44. In a transformer the resistance between its primary and secondary should be

Zero
1 ohm
1000 ohms
Infinity

Detailed SolutionIn a transformer the resistance between its primary and secondary should be

45. The efficiency of a transformer, under heavy loads, is comparatively low because

copper loss becomes high in proportion to the output
iron loss is increased considerably
voltage drop both in primary and secondary becomes large
secondary output is much less as compared to primary input

Detailed SolutionThe efficiency of a transformer, under heavy loads, is comparatively low because

46. The leakage flux in a transformer depends upon

load current
load current and voltage
load current, voltage and frequency
load current, voltage, frequency and power factor

Detailed SolutionThe leakage flux in a transformer depends upon

47. For the parallel operation of single phase transformers it is necessary that they should have

same efficiency
same polarity
same kVA rating
same number of turns on the secondary side.

Detailed SolutionFor the parallel operation of single phase transformers it is necessary that they should have

48. Natural air cooling is generally restricted for transformers up to

1.5 MVA
5 MVA
15 MVA
50 MVA

Detailed SolutionNatural air cooling is generally restricted for transformers up to

49. The transformer oil should have _____ volatility and _____ viscosity.

low,low
high,high
low,high
high,low

Detailed SolutionThe transformer oil should have _____ volatility and _____ viscosity.

50. In the transformer following winding has got more cross-sectional area

Low voltage winding
High voltage winding
Primary winding
Secondary winding

Detailed SolutionIn the transformer following winding has got more cross-sectional area

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