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

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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

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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
D.

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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
D.

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61.  Regulation of a good transformer should be near
A.1%
B.10%
C.20%
D.30%

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

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63. In Scott connection, if the ratio of the main transformer is k, then the teaser transformer has transformation ratio of
A.N,2
B.NI
C. x2 (712'
D. x2 N2

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