A.reduce hysteresis loss
B.reduce eddy current losses
C.reduce copper losses
D.reduce all above losses
Answer: B
2. In the transformer following winding has got more cross-sectional area
A.Low voltage winding
B.High voltage winding
C.Primary winding
D.Secondary winding
Answer: A
3. The transformer laminations are insulated from each other by
A.mica strip
B.thin coat of varnish
C.paper
D.any of the above
Answer: B
4. Buchholz's relay gives warning and protection against
A.electrical fault inside the transformer itself
B.electrical fault outside the transformer in outgoing feeder
C.for both outside and inside faults
D.none of the above
Answer: A
5. If R₂ is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be
A.R₂/√K
B.R₂/K²
C.R₂²/K²
D.R₂²/K
Answer: B
6. Two transformers operating in parallel will share the load depending upon their
A.leakage reactance
B.per unit impedance
C.efficiencies
D.ratings
Answer: B
7. Which of the following does not change in an ordinary transformer?
A.Frequency
B.Voltage
C.Current
D.Any of the above
Answer: A
8. When a given transformer is run at its rated voltage but reduced frequency, its
A.flux density remains unaffected
B.iron losses are reduced
C.core flux density is reduced
D.core flux density is increased
Answer: D
9. Which of the following does not change in a transformer?
A.Current
B.Voltage
C.Frequency
D.All of the above
Answer: C
10. The starting torque of a squirrel-cage induction motor is
A.low
B.negligible
C.same as full-load torque
D.slightly more than full-load torque
Answer: A
11. 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
Answer: B
12. During short circuit test iron losses are negligible because
A.the current on secondary side is negligible
B.the voltage on secondary side does not vary
C.the voltage applied on primary side is low
D.full-load current is not supplied to the transformer
Answer: C
13. If a transformer is continuously operated the maximum temperature rise will occur in
A.core
B.windings
C.tank
D.any of the above
Answer: B
14. The primary coil of a transformer is connected to a 60 V ac source. The secondary coil is connected to a 330 Ω load. The turns ratio is 3:1. What is the secondary voltage?
A.2 V
B.20 V
C.180 V
D.18 V
Answer: B
15. The use of higher flux density in the transformer design
A.reduces weight per kVA
B.reduces iron losses
C.reduces copper losses
D.increases part load efficiency
Answer: A
16. A transformer has a 1:6 turns ratio and a secondary coil load resistance of 470 Ω. The load resistance as seen by the source is
A.1.3 Ω
B.7.8 Ω
C.78 Ω
D.13 Ω
Answer: D
17. In a transformer the tappings are generally provided on
A.primary side
B.secondary side
C.low voltage side
D.high voltage side
Answer: D
18. 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°
Answer: A
19. The purpose of providing iron core in a step-up transformer is
A.To provide coupling between primary and secondary
B.To increase the magnitude of mutual flux
C.To decrease the magnitude of magnetizing current
D.To provide all above features
Answer: C
20. Which of the following is not the standard voltage for power supply in India?
A.llkV
B.33kV
C.66 kV
D.122 kV
Answer: D
21. When the equivalent circuit diagram of doouble squirrelcage induction motor is constructed the two cages can be considered
A.in series
B.in parallel
C.in series-parallel
D.in parallel with stator
Answer: Option B
22. An ideal transformer has infinite values of primary and secondary inductances. The statement is
A.true
B.false
A.llkV
B.33kV
C.66 kV
D.122 kV
Answer: D
21. When the equivalent circuit diagram of doouble squirrelcage induction motor is constructed the two cages can be considered
A.in series
B.in parallel
C.in series-parallel
D.in parallel with stator
Answer: Option B
22. An ideal transformer has infinite values of primary and secondary inductances. The statement is
A.true
B.false
Answer: B
23. During open circuit test of a transformer
A.primary is supplied rated voltage
B.primary is supplied full-load current
C.primary is supplied current at reduced voltage
D.primary is supplied rated kVA
Answer: A
24. 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
Answer: C
25. A transformer can have zero voltage regulation at
A. leading power factor
B. lagging power factor
C. unity power factor
D. zero power factor
Answer: A
26. The secondary of a current transformer is always short-circuited under operating conditions because it
A. avoids core saturation and high voltage induction
B. is safe to human beings
C. protects the primary circuit
D. none of the above
Answer: A
27. The 'cogging' of an induction motor can be avoided by
A. proper ventilation
B. using DOL starter
C. auto-transformer starter
D. having number of rotor slots more or less than the number of stator slots (not equal)
Answer: D
28. Which of the following is not a part of transformer installation?
A. Conservator
B. Breather
C. Buchholz relay
D. Exciter
Answer: D
29. Which winding of the transformer has less cross-sectional area?
A. Primary winding
B. Secondary winding
C. Low voltage winding
D. High voltage winding
Answer: D
30. The complete circle diagram of induetion motor can be drawn with the help of data found from
A. noload test
B. blocked rotor test
C. stator resistance test
D. all of the above
Answer: D
31. A common method of cooling a power transformer is
A. natural air cooling
B. air blast cooling
C. oil cooling
D. any of the above
Answer: C
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