electrical machine design MCQs – Page 5

Practise focused electrical machine design questions with marked answers for exam preparation and subject revision.

electrical machine design Mcqs

81. The change in flux linkages can be caused in which of the following ways ?
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A. The flux is constant with respect to time and is stationary and the coil moves through it

B. The coil is stationary with respect to flux and the flux varies in magnitude with respect to time

C. Both the changes mentioned above occur together, i.e., the coil moves through a time varying field

D. All of the above

82. Hydrogen has a heat transfer co-efficient __________ times that of air?
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A. 3.5

B. 4.5

C. 2.5

D. 1.5

83. ____________ is the common method of applying brushes to the commntator?
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A. Reaction

B. Trailing

C. Radial

D. All of the above

84. In direct cooled system using hydrogen both stator and rotor conductors are made____________?
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A. solid

B. hollow

C. perforated

D. any ofthe above

85. Multi-layer helical windings are commonly used in the transformers as high voltage windings_______________?
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A. upto 80 kV

B. upto 20 kV

C. upto 50 kV

D. for 110 kV and above

86. The mcrease in heat dissipation by air blasts is due to increase in______________?
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A. any ofthe above

B. convection

C. conduction

D. radiation

87. The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ?
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A. Conduction

B. All of the above

C. Radiation

D. Convection

88. electromagnets generally function as holding magnets ?
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A. None of the above

B. Portative

C. Either of the above

D. Tractive

89. The design of mechanical parts is particularly important in case of __________ speed machines?
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A. any of the above

B. high

C. medium

D. low

90. Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto_______________?
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A. 60 MW

B. 10 MW

C. 150 MW

D. 30 MW

91. cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall______________?
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A. Indirect

B. Any of the above

C. Direct

D. Conventional

92. ___________ brushes are fragile and cause excessive wear of commutator?
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A. Electro graphitic

B. Hard carbon

C. Natural graphite

D. Metal graphite

93. D.C. servomotors are used in______________?
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A. purely D.C. control systems

B. purely AC. control systems

C. both D.C. and AC. control systems

D. none of the above

94. In self cooled motors the cooling time constant is about ___________ than the heating time constant because cooling conditions are worse at standstill?
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A. 4 to 5 times greater

B. none of the above

C. 3 to 4 times greater

D. 2 to 3 times greater

95. The efficiency of a machine should be as ____________ as possible to reduce the operating cost?
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A. high

B. none of the above

C. either of the above

D. low

96. Aluminium when adopted as a conductor material in __________ transformers, decreases the overall cost of the transformer?
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A. large size

B. any of the above size

C. medium size

D. small size

97. For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used?
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A. 2.2 to 3.2 A/mm2

B. 1.5 to 2.0 A/mm2

C. 3.2 to 4.2 A/mm2

D. 1.0 to 1.2 A/mm2

98. Dummy coil should not be used in_________________?
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A. small machines

B. none of the above

C. large machines

D. either A. or B.

99. The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are______________?
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A. 0.8 to 1.0 Wb/m2

B. 0.5 to 0.8 Wb/m2

C. 1.4 to 1.8 Wb/m2

D. 1.1 to 1.35 Wb/m2

100. Which of the following is the major consideration to evolve a good design ?
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A. Durability

B. All of the above

C. Compliance with performance criteria as laid down in specifications

D. Cost

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