Index

SymbolsTransformerRelayPower-SystemBasic-electricalACSR-ConductorCircuit-BreakerInterview-questions-of-Basic-ElectricityInterview-questions-of-transformerInsulatorCurrent-TransformerMCQMCQ-powersystemThermal-power-stationInterview-questions-of-Power-SystemPower-ElectronicsInterview-questions-of-Underground-CableInterview-questions-of-IlluminationIlluminationMCQ-of-ElectronicsMCQ-of-Basic-ElectricalMCQ-of-Transformers MCQ-of-D.C-motor MCQ-of-D.C-generatorsMCQ-Control-SystemMCQ-Measurementsmcq-of-Generation-power-systemMCQ-of-Induction-MotorMCQ-of-Transmission-DistributionMCQ-of-Electrical-MachinesMCQ-of-Alternator-and-Synchronous-MotorsMCQ-Electric-PowerMCQ-Illumination

MCQ of Transformer page-20


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91. All day efficiency of a distribution transformer is ………. its commercial efficiency.

A) Lower than
B) Equal to
C) Higher than
D) Any of these.

Ans : (A)

92. A 480/120 V, 5 kVA two winding transformer is to be used as an autotransformer to supply power at 480 V from 600 V source. The kVA capacity as autotransformer will be

A) 25 kVA
B) 20 kVA
C) 15 kVA
D) 10 kVA.

Ans : (A)

93. The maximum load that a power transformer can carry is limited by its

A) dielectric strength of oil
B) temperature rise
C) copper loss
D) voltage ratio.

Ans : (B)

94. In a three-phase transformer, the phase difference between the primary and the induced secondary emf is

A) 90°
B) 120°
C) 180°
D) 360°

Ans : (C)

95. When the transformer core is made of copper, which of the following loss will be more ?

A) Eddy current loss
B) Thermal loss
C) Hysteresis loss
D) Copper loss.

Ans : (A)

96. Porcelain bushings on transformers are normally not used beyond

A) 11 kV
B) 66 kV
C) 132 kV
D) 220 kV.

Ans : (A)

97. The secondary of a current transformer under operating conditions is short-circuited to avoid

A) high voltage surge
B) core saturation and high voltage induction
C) insulation break-down
D) break in primary winding.

Ans : (B)

98. The voltage regulation of a transformer can be zero when the power factor is

A) lagging
B) leading
C) 0.5
D) unity.

Ans : (B)

99. The harmonic currents in transformer increase all of the following EXCEPT :

A) Secondary voltage
B) Magnetic interference with protective relays
C) Core loss
D) Copper loss.

Ans : (A)

100. The value of useful flux least depends on

A) load
B) voltage
C) magnetomotive force
D) all of the above.

Ans : (A)


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