1. While conducting short-circuit test on a transformer the following side is short circuited

(a) High voltage side
(b) Low voltage side

(c) Primary side
(d) Secondary side

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Answer. b

2. Which of the following is not a part of transformer installation?

(a) Conservator
(b) Breather
(c) Buchholz relay
(d) Exciter

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Answer. d

3. The purpose of providing an iron core in a transformer is to

(a) provide support to windings
(b) reduce hysteresis loss
(c) decrease the reluctance of the magnetic path
(d) reduce eddy current losses

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Answer. c

4. No-load current in a transformer

(a) lags behind the voltage by about 75°
(b) leads the voltage by about 75°
(c) lags behind the voltage by about 15°
(d) leads the voltage by about 15°

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Answer. a

 

5. The efficiency of a transformer will be maximum when

(a) copper losses = hysteresis losses
(b) hysteresis losses = eddy current losses
(c) eddy current losses = copper losses
(d) copper losses = iron losses

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Answer. d

6. The permissible flux density in case of cold rolled grain oriented steel is around

(a) 1.7 Wb/m2
(b) 2.7 Wb/m2
(c) 3.7 Wb/m2
(d) 4.7 Wb/m2

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Answer. a

7. Sumpner’s test is conducted on transformers to determine

(a) temperature
(b) stray losses
(c) all-day efficiency
(d) none of the above

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Answer. a

8. The dielectric strength of transformer oil is expected to be

(a) 1 kV
(b) 33 kV
(c) 100 kV
(d) 330 kV

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Answer. b

9. No-load on a transformer is carried out to determine

(a) copper loss
(b) magnetising current
(c) magnetising current and loss
(d) efficiency of the transformer

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Answer. c

10. The path of a magnetic flux in a transformer should have

(a) high resistance
(b) high reluctance
(c) low resistance
(d) low reluctance

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Answer. d

11. The no-load current drawn by the transformer is usually what per cent of the full-load current?

(a) 0.2 to 0.5 per cent
(b) 2 to 5 per cent
(c) 12 to 15 per cent
(d) 20 to 30 per cent

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Answer. b

12. The degree of mechanical vibrations produced by the laminations of a transformer depends on

(a) tightness of clamping
(b) gauge of laminations
(c) size of laminations
(d) all of the above

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Answer. d

13. A transformer core is laminated to

(a) reduce hysteresis loss
(b) reduce eddy current losses
(c) reduce copper losses
(d) reduce all above losses

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Answer. b

14. In a transformer, the energy is conveyed from primary to secondary

(a) through cooling coil
(b) through air
(c) by the flux
(d) none of the above

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Answer. c

 

15. Which of the following does not change in a transformer?

(a) Current
(b) Voltage
(c) Frequency
(d) All of the above

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Answer. c

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