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MCQ of Transformer page-6


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51. The direction of the central phase winding of a three-phase shell type transformer is reversed with respect to the outer phases to

a) Save considerable amount of core material
b) Reduce short circuit forces
c) Reduce leakage flux
d) Minimize eddy current loss

Ans: (a)

52. In a transformer, spiral winding is suitable only for windings

a) Rated for high voltage
b) Rated for low voltage
c) Carrying very high current
d) Carrying very low current

Ans: (c)

53. In a transformer, continuous disc winding is suitable for

a) High voltage winding of small trans-formers
b) Low voltage winding of small trans-formers
c) High voltage winding of large trans-formers
d) Low voltage winding of large trans-formers

Ans: (c)

54. For transformation ration k, the transformer secondary impedance has to be multiplied by the following factor to get its equivalent primary impedance

a) K
b) 1/k
c) k2
d) 1/k2
Ans: (c)

55. The magnetic flux in a transformer follows a path of

a) Low reluctance
b) High conductivity
c) High reluctance
d) Low conductivity

Ans: (a)

56. Use of higher flux density in trans-former design

a) Increases the weight/kVA
b) Decreases the weight/kVA
c) Reduces iron losses
d) Improves insulation

Ans: (b)

57. A transformer is connected to a constant voltage supply. As the supply frequency increases, the magnetic flux in the core

a) Decreases
b) Increases toward saturation
c) Becomes zero
d) Becomes constant

Ans: (b)

58. Circular coil sections are generally used in transformer because they

a) Have the toughest mechanical shape
b) Are easy to wound
c) Reduce copper losses
d) Reduce iron losses

Ans: (a)

59. Good transformer oil should contain water less than

a) 4 ppm
b) 8 ppm
c) 12 ppm
d) 20 ppm

Ans: (b)

60. Stepped core limbs are used to

a) Reduce copper material and copper losses
b) Reduce iron material and iron losses
c) Both (a) and (b)
d) Increase mechanical strength of the core

Ans: (a)


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