Transformers Archives

71. A shell-type transformer has

high eddy current losses

reduced magnetic leakage

negligibly hysteresis losses

none of the above

Detailed SolutionA shell-type transformer has

72. Power transformers are designed to have maximum efficiency at

nearly full load

70% full load

50% full load

no load

Detailed SolutionPower transformers are designed to have maximum efficiency at

73. The efficiency of a transformer will be maximum when

copper losses = hysteresis losses

hysteresis losses = eddy current losses

eddy current losses = copper losses

copper losses = iron losses

Detailed SolutionThe efficiency of a transformer will be maximum when

74. Which of the following is not the standard voltage for power supply in India?

llkV

33kV

66 kV

122 kV

Detailed SolutionWhich of the following is not the standard voltage for power supply in India?

75. Reduction in core losses and increase in permeability are obtained with transformer employing

core built-up of laminations of cold rolled grain oriented steel

core built-up of laminations of hot rolled sheet

either of the above

none of the above

Detailed SolutionReduction in core losses and increase in permeability are obtained with transformer employing

76. Harmonics in transformer result in

Increased core losses

Increased I2R losses

Magnetic interference with communication circuits

All of the above

Detailed SolutionHarmonics in transformer result in

77. Minimum voltage regulation occurs when the power factor of the load is

unity

lagging

leading

zero

Detailed SolutionMinimum voltage regulation occurs when the power factor of the load is

78. Open circuit test on transformers is conducted to determine

hysteresis losses

copper losses

core losses

eddy current losses

Detailed SolutionOpen circuit test on transformers is conducted to determine

79. The function of conservator in a transformer is

to project against internal fault

to reduce copper as well as core losses

to cool the transformer oil

to take care of the expansion and contraction of transformer oil due to variation of temper-ature of sur-roundings

Detailed SolutionThe function of conservator in a transformer is

80. What will happen if the transformers working in parallel are not connected with regard to polarity?

The power factor of the two transformers will be different from the power factor of common load

Incorrect polarity will result in dead short circuit

The transformers will not share load in proportion to their kVA ratings

none of the above

Detailed SolutionWhat will happen if the transformers working in parallel are not connected with regard to polarity?

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