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MCQ of Transformer page-17


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61. As a general rule, the kVA rating ratio of transformers operating in parallel should be within

A) 5 : 1
B) 4 : 1
C) 3 : 1
D) 2 : 1.

Ans : (C)

62. The no load p.f. of transformer is small because

A) Magnetizing component of Io is large
B) Magnetizing component of Io is small
C) Iron loss component of Io is large
D) Copper losses are high.

Ans : (A)

63. Which value of flux is involved in the emf equation of the transformer ?

A) Critical value
B) RMS value
C) Average value
D) Maximum value.

Ans : (D)

64. Which of the following loss in a transformer is zero even at full load ?

A) friction loss
B) core loss
C) hysteresis loss
D) eddy current loss.

Ans : (A)

65. For the same rating which of the following sets will be costly ?

A) Both will have identical cost
B) Three phase transformer
C) Three transformers each of the single phase type
D) None of the above.

Ans : (C)

66. In a transformer, the tapping are usually provided on

A) high voltage side
B) low voltage side
C) secondary side
D) primary side.

Ans : (A)

67. Two transformers T1 and T2 have identical ratings. Transformer T1 is designed for flux density of 1.15 Wb/m2 and transformer T2 is designed for flux density of 1.45 Wb/m2. From the above information it can be concluded that

A) both transformers will operate at 0.8 p.f. lagging
B) both transformers will have identical losses at full load
C) the regulation of transformer T1 will be better than that of transformer T2
D) the weight of transformer T1 will be more than that of transformer T2.

Ans : (D)

68. Two single phases 100 kVA transformers, each having different leakage, impedance, are connected in parallel. When a load of 150 kVA at 0.8 p.f. lagging is applied

A) both transformers will operate at identical power factor
B) one of the transformers will operate at p.f. more than 0.8 lagging and other will operate at p.f. less than 0.8 lagging
C) both transformers will operate at power factor less than 0.8 lagging
D) both transformers will operate at power factor more than 0.8 lagging.

Ans : (A)

69. The operation of an ideal transformer is based on the assumption (s) that.

A) There is no saturation of core
B) There is no leakage flux
C) The resistance of the winding is negligible
D) All of the above.

Ans : (B)

70. The voltage transformation ratio of a transformer.

A) E2/E1
B) E1/E2
C) I2/I1
D) N1/N2.

Ans : (B)


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