Chapter 7: Transformer- Single and Three phase
51. When the secondary of the transformer is loaded, the primary current will
A. not be effected
B. increase
C. be less than the secondary current
D. be the vector sum of no load current and additional current drawn due to the secondary current
...
Answer is (D)
52. A single phase transformer has turn ratio of
10. The primary winding has resistance of 2.2 ohms and the secondary
winding has resistance of 0.030. The total resistance as referred to the
primary is
A. 2.5 Ω
B. 5.2 Ω
C. 2.23 Ω
D. 2.203 Ω
53. At full load, the copper loss in a transformer is 600 watts. At half load, the copper load will be
A. 300 watts
B. 150 watts
C. 75 watts
D. 600 watts
...
Answer is (B)
54. Power transformers are usually designed to have maximum efficiency at
A. a little more than full load
B. near full load
C. half load
D. quarter load
...
Answer is (C)
55. The all-day efficiency of a transformer depends primarily on
A. its copper loss
B. the amount of load
C. the duration of load
D. both (b) and (c) above
56. Which of the following test on a transformer provides information about regulation, efficiency and heating under load condition?
A. open circuit test
B. back-to-back test
C. Hopkinson Test
D. short circuit test
...
Answer is (B)
57. Zero regulation in a transformer results when power factor of the load is
A. zero
B. unity
C. Xeq/Zeq leading
D. Xeq/Zeq lagging
59. Buchholz relay is usually not provided on transformers of rating below
A. 5 kVA
B. 50 kVA
C. 100 kVA
D. 500 kVA
60. Scott connections are used for
A. single-phase to three-phase transformation
B. three-phase to single-phase transformation
C. three-phase to three-phase & two-phase transformations
D. any of the above
...
Answer is (C)
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