141.  Which of the following is not a routine test on transformers?
A. Core insulation voltage test
B. Impedance test
C. Radio interference test
D. polarity test

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142.  A transformer can have zero voltage regulation at
A. leading power factor
B. lagging power factor
C. unity power factor
D. zero power factor

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143. Helical coils can be used on
A. low voltage side of high kVA transformers
B. high frequency transformers
C. high voltage side of small capacity transformers
D. high voltage side of high kVA rating transformers

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144.  The core used in high frequency transformer is usually
A. copper core
B. cost iron core
C. air core
D. mild steel core

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145.  The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be
A. 6400W
B. 1600W
C. 800 W
D. 400 W

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146.  The value of flux involved in the e.m.f. equation of a transformer is
A. average value
B. r.m.s. value
C. maximum value
D. instantaneous value

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147.  Silicon steel used in laminations mainly reduces
A. hysteresis loss
B. eddy current losses
C. copper losses
D. all of the above

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