ONLINE Multiple Choice Questions – Electric Machine Design PART 7

91. The disadvantage of cylindrical winding is
(A) increased eddy current loss
(B) high copper loss
(C) low mechanical strength
(D) all of the above.

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92. For transformer laminations
(A) hot rolled silicon steel is preferred
(B) cold rolled silicon steel is preferred
(C) grain oriented silicon steel is preferred
(D) any of the above steel can be used.

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93. The percentage of silicon in the core steel is
(A) 1 to 2 percent
(B) 2 to 3 percent
(C) 4 to 6 percent
(D) 8 to 10 percent.

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94. The stacking factor will be least for
(A) Square core
(B) Cruciform core
(C) Three stepped core
(D) Four stepped core.

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95. In static transformers mechanical forces are produced due to
(A) vibrations
(B) gap between laminations
(C) interaction of current flowing in the conductor and leakage flux around it.
(D) none of the above.

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96. The thickness of laminations of the core of a power transformer usually
(A) 0.003 to 0.05 mm
(B) 0.03 to 0.05 mm
(C) 0.03 to 0.5 mm
(D) 3 to 5 mm.

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97. Transformer action requires a
(A) short circuiting
(B) increasing resistivity
(C) reducing resistivity
(D) all of the above.

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98. In an oil filled transformer, oil is provided for
(A) Cooling
(B) Insulation
(C) Lubricating
(D) Both cooling and insulation
(E) Preventing accumulation of dust.

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99. The dimensions of a dc machine primarily depend on
(A) kW output
(B) work done per revolution
(C) exposed surface
(D) none of the above.

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Questions 100 to 104 are based on data below:

The various losses of a 60 HD, 220 V 850 rpm dc motor are as
follows: – Copper losses 3.2 kW, core losses 0.8 kW, mechanical losses
0.1 kW. Now let us consider another dc machine otherwise similar to this
machine but having its linear dimensions 1.5 times.

100. The copper losses of new machine will be
(A) 1.5 x 3.2 kW
(B) (1.5)2 x 3.2 kW
(C) (1.5 )3 x 3.2 kW
(D) 1/(1.5)2 x3.2 kW

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101. The iron losses of new machine will be
(A) (1.5) x 0.8 kW
(B) (1.5)2 x 0.8 kW
(C) (1.5)4 x 0.8 kW
(D) (1.5)5x 0.8 kW

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102. The mechanical losses will be
(A) 1.5 x 0.1 kW
(B) (1.5)2 x 0.1 kW
(C) (1.5)3 x 0.1 kW
(D) 1/ (1.5)2 x 0.1 kW

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A

103. The rating of the new machine will be
(A) 1.5 x 60 HP
(B) (1.5)2 x60 HP
(C) (1,5)3 x 60 HP
(D) (1.5)4 x 60 HP.

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104. The efficiency of the new machine will be
(A) 88.8%
(B) 91.7%
(C) 94.5%
(D) 96.7%.

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105. The diameter of a 10 SWG wire will be closer to
(A) 0.1 mm
(B) 1mm
(C) 3 mm
(D) 13 mm.

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ONLINE Multiple Choice Questions - Electric Machine Design PART 8
ONLINE Multiple Choice Questions - Electric Machine Design PART 6

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