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Electrical Engineering Objective Questions { Transformers }

57. 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

58. 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

59. 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
B.(c) Hopkinson test
C.(d) short circuit test

60. 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

61.  Regulation of a good transformer should be near

62. Buchholz relay is usually not provided on transformers of rating below
A. 5 kVA
B. 50 kVA
C. 100 kVA
D. 500 kVA

63. In Scott connection, if the ratio of the main transformer is k, then the teaser transformer has transformation ratio of
C. x2 (712'
D. x2 N2

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