1. Which of the following Transformer can have tap changer?
(a) Current transformer.
(b) Potential transformer.
(c) Power transformer.
(d) Earthing transformer. Answer
2. The degree of mechanical vibrations produced by the lamination of a transformer depends on
(a) tightness of clamping.
(b) gauge of laminations.
(c) size of laminations.
(d) all of the above. Answer
3. When the square wave is given to primary to a transformer then secondary will gives
(a) no waveform.
(b) square waveform.
(c) pulse waveform.
(d) sine waveform. Answer
4. The efficiency of two identical transformers under loaded conditions can be determined by
(a) short-circuit test.
(b) back-to-back test.
(c) open circuit test.
(d) any of the above. Answer
5. Which of the following special transformer is used to convert unbalanced signal to balanced signal?
(a) Isolation transformer.
(b) Auto transformer.
(c) Balun.
(d) Center tapped transformer. Answer
6. When the iron losses of a distribution transformer decreases, then its all day efficiency
(a) decreases.
(b) increases.
(c) unaffected
(d) none of the above. Answer
7. The main purpose of using core in a transformer is to
(a) decrease iron losses.
(b) prevent eddy current loss.
(c) eliminate magnetic hysteresis.
(d) decrease reluctance of the common magnetic circuit. Answer
8. The functions of using stepped core in transformer is to reduce
(a) hysteresis losses.
(b) eddy current losses.
(c) volume of copper.
(d) reluctance of core. Answer
9. When the transformer is loaded then the secondary terminal voltage will fall for
(a) lagging power factor.
(b) unity power factor.
(c) leading power factor.
(d) lagging and leading power factor. Answer
10. Which part of the transformer is most affected by the overheating?
(a) winding of transformer.
(b) winding insulation.
(c) transformer core.
(d) transformer tank. Answer
11. In a star-delta transformer, the delta side phase voltage leads the star sides phase voltage by an angle
(a) + 30°.
(b) + 45°.
(c) – 30°.
(d) – 45°. Answer
12. Minimum voltage regulation occurs when the power factor of the load is
(a) unity.
(b) lagging.
(c) leading.
(d) zero. Answer
13. The chemical used in breather of a transformer should have property of
(a) absorbing heat.
(b) ionizing air.
(c) absorbing moisture.
(d) cleaning oil. Answer
14. The power transformer can be termed as a constant
(a) voltage device.
(b) current device.
(c) power device.
(d) main flux device. Answer
15. In a transformer, which of the following losses are zero?
(a) Hysteresis losses.
(b) Eddy current losses.
(c) Copper losses.
(d) Frictional and windage losses. Answer