ONLINE Multiple Choice Questions – Electric Machine Design PART 8

106. Tap changing facility is generally provided on
(A) high voltage transformers
(B) distribution transformers
(C) current transformers
(D) step up transformers.

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107. In case of air natural cooling, the cooling surface increases as the __________ of the size
(A) inverse
(B) inverse square
(C) square
(D) cube.

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108. In case of air natural cooling the losses increase as the __________ of the size
(A) inverse
(B) inverse square
(C) square
(D) cube.

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109. The heat generated in the transformer is dissipated to the surroundings mainly by
(A) conduction
(B) convection
(C) radiation
(D) all of the above.

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110. The heat transfer by convection least depends on
(A) temperature difference
(B) air velocity
(C) surface area
(D) color of the paint.

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111. Oil for transformer cooling should have low
(A) dielectric strength
(B) viscosity
(C) flash point.

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112. Oil for transformer cooling should have high
(A) flash point
(B) viscosity
(C) sludging tendencies
(D) moisture content.

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113. The oil selected for transformer cooling should be free from
(A) alkalies
(B) acids
(C) sulphur
(D) all of the above.

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114. Normally for the design of transformer the ambient temperature is taken as
(A) 20°C
(B) 25°C
(C) 45°C
(D) 75°C.

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115. A transformer is designed for certain ambient
temperature. If it actually operates at a temperature 10°C above the
design temperature its kVA rating should be
(A) increased by 10%
(B) reduced by 5%
(C) reduced by 10%
(D) reduced by 20%.

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116. The overload capacity of a transformer depends on
(A) ratio of full load copper losses to its iron losses
(B) size of the core
(C) frequency
(D) none of the above.

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117. Which surge will be most damaging for a transformer ?
(A) steeper front flatter tail
(B) flatter front steeper tail
(C) uniform
(D) all will be equally damaging.

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118. A transformer is considered to have a network of series capacitance due to
(A) inter-turn insulation
(B) earthing
(C) laminated core
(D) surrounding tanks.

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119. In a transformer the shunt capacitance is decreased and series capacitance is increased by the use of
(A) shielded windings
(B) inter-leaved winding
(C) layer type winding
(D) any of the above.

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120. An air core transformer as compared to iron-core transformer has
(A) Less magnetic core loss
(B) More magnetic core loss
(C) No magnetic core loss
(D) Less ohmic loss.

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ONLINE Multiple Choice Questions - Electric Machine Design PART 9
ONLINE Multiple Choice Questions - Electric Machine Design PART 7

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