MCQs on transformer 61-80

61. The use of higher flux density in the transformer design
(a) reduces weight per kVA✔
(6) reduces iron losses
(c) reduces copper losses
(d) increases part load efficiency

62. The chemical used in breather for transformer should have the quality of
(a) ionizing air
(b) absorbing moisture✔
(c) cleansing the transformer oil
(d) cooling the transformer oil.

63. The chemical used in breather is
(a) asbestos fiber
(b) silica sand
(c) sodium chloride
(d) silica gel✔

64. An ideal transformer has infinite values of primary and secondary inductances. The statement is
(a) true
(b) false✔

65. The transformer ratings are usually expressed in terms of
(a) volts
(b) amperes
(c) kW
(d) kVA✔

66. The noise resulting from vibrations of laminations set by magnetic forces, is termed as
(a) magnetostrication
(b) boo
(c) hum✔
(d) zoom

67. Hysteresis loss in a transformer varies as CBmax = maximum flux density)
(a) Bmax
(b) Bmax1-6✔
(C) Bmax1-83
(d) B max

68. Material used for construction of transformer core is usually
(a) wood
(b) copper
(c) aluminium
(d) silicon steel✔

69. The thickness of laminations used in a transformer is usually
(a) 0.4 mm to 0.5 mm✔
(b) 4 mm to 5 mm
(c) 14 mm to 15 mm
(d) 25 mm to 40 mm

70. The function of conservator in a transformer is
(a) to project against’internal fault
(b) to reduce copper as well as core losses
(c) to cool the transformer oil
(d) to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings✔

71. The highest voltage for transmitting electrical power in India is
(a) 33 kV.
(6) 66 kV
(c) 132 kV
(d) 400 kV✔

72. In a transformer the resistance between its primary and secondary is
(a) zero
(b) 1 ohm
(c) 1000 ohms
(d) infinite✔

73. A transformer oil must be free from
(a) sludge
(b) odour
(c) gases
(d) moisture✔

74. A Buchholz relay can be installed on
(a) auto-transformers
(b) air-cooled transformers
(c) welding transformers
(d) oil cooled transformers✔

75. Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds
(a) 150°C✔
(b) 80°C
(c) 100°C
(d) 50°C

76. The main reason for generation of harmonics in a transformer could be
(a) fluctuating load
(b) poor insulation
(c) saturation of core✔
(d) mechanical vibrations

77. Distribution transformers are generally designed for maximum efficiency around
(a) 90% load
(b) zero load
(c) 50% load✔
(d) 25% load

78. Which of the following property is not necessarily desirable in the material for transformer core ?
(a) Mechanical strength
(6) Low hysteresis loss
(c) High thermal conductivity✔
(d) High permeability

79. Star/star transformers work satisfactorily when
(a) load is unbalanced only
(b) load is balanced only✔
(c) on balanced as well as unbalanced loads
(d) none of the above

80. Delta/star transformer works satisfactorily when
(a) load is balanced only
(b) load is unbalanced only
(c) on balanced as well as unbalanced loads✔
(d) none of the above