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Electrical Engineering Objective Questions { Transformers }



92. Buchholz relay works on the principle of
A. production of eddy currents whenever load changes are rapid
B. ionization of transformers oil
C. magnetic hum due to sudden variation in load
D. generation of gas due to breakdown of the insulation.

93. Which of the following transformers is smallest?
A. 1 kVA, 50 Hz
B. 1 kVA, 200 Hz
C. 1 kVA, 400 Hz (d) I kVA, 600 Hz
D.

94. In parallel operation of two single phase transformers, if the impedance triangles of the transformers are not identical in shape and size.
A. power factors at which the transformers operate will be same but different from power factor of common load
B. power factors at which the transformers operate and power factor of common load all will be same.
C. power factor of one transformer and power factor of common load will be same.
D. power factors at which the transfomers operate will be different from one another and again these will be different from power factor of common load.

95. A 100 kVA transformer has copper loss of 1000 W at full load and iron loss of 1000 watts. At half the full load and 0.8 Power factor (lagging), the efficiency of the transformer will be nearly
A.98.91%
B.96.97%
C.95%
D.91.91%

96. Eddy current losses in a transformer may be reduced by
A. decreasing the thickness of laminations
B. increasing the thickness of laminations
C. decreasing the air gap in the magnetic circuit.
D. using wire of higher gauge for winding the transformer.

97. The magnetic flux in a transformer follows a path of
A. high reluctance
B. low reluctance
C. high conductivity
D. low conductivity

98. In a transformer, the primary and the secondary voltage are
A. 600 out of phase
B. 900 out of phase
C. 1800 out of phase
D. always in phase

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