421. A transformer can have zero voltage regulation at______________?
A. leading power factor
B. lagging power factor
C. unity power factor
D. zero power factor

422. An ideal transformer will have maximum efficiency at a load such that?
A. copper loss = iron loss
B. copper loss iron loss
D. none of the above

423. 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

424. If the supply frequency to the transformer is increased,”the iron loss will__________?
A. not change
B. decrease
C. increase
D. any of the above

425. 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

426. Negative voltage regulation is indicative that the load is___________?
A. capacitive only
B. inductive only
C. inductive or resistive
D. none of the above

427. Which of the following loss in a transformer is zero even at full load ____________?
A. Core loss
B. Friction loss
C. Eddy current loss
D. Hysteresis loss

428. Iron loss of a transformer can be measured by____________?
A. low power factor wattmeter
B. unity power factor wattmeter
C. frequency meter
D. any type of wattmeter

429. Which of the following is the most likely source of harmonics in a transformer ?
A. poor insulation
B. Overload
C. loose connections
D. Core saturation

430. If a transformer is continuously operated the maximum temperature rise will occur in_______________?
A. core
B. windings
C. tank
D. any of the above

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