Electric Machine Design PART 5
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Attempt Free Electric Machine Design PART 5 Here. Read The Important Electrical MCQ From Below.
61. The percentage of overload on a continuous rating machine is
(A) zero
(B) 5%
(C) 10%
(D) 50%.
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62. Open circuit test on a transformer is conducted to obtain
(A) the leakage impedances
(B) the ohmic loss
(C) hysteresis loss only
(D) core loss only
(E) eddy current loss only.
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63. Heat transfer capability of hydrogen is nearly __________ times that of air
(A) 2
(B) 3
(C) 7
(D) 17.
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Electric Machine Design PART 5
64. The density of hydrogen is __________ that of air
(A) 14
(B) 1/4
(C) 1/7
(D) 1/14
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65. Turbo-alternators of rating __________ and above are normally hydrogen cooled.
(A) 10 MW
(B) 20 MW
(C) 25 MW
(D) 50 MW.
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66. Iron losses of a machine are
(A) directly proportional to flux density
(B) directly proportional to the square of flux density
(C) inversely proportional to flux density
(D) inversely proportional to the square of flux density.
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67. While considering hysteresis loss in a transformer, under which of the following the loss will not increase ?
(A) when flux density is increased by 10%
(B) when thickness of lamination is caused by 10%
(C) when frequency is increased by 10%
(D) when both thickness and frequency are increased by 10%.
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Electric Machine Design PART 5
68. The shaft of electric motors is generally made of
(A) mild steel
(B) cast iron
(C) copper
(D) aluminium alloy.
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69. The critical speed of the shaft for an electric motor should be
(A) away from the operating speed
(B) exactly the same as operating speed
(C) half the operating speed
(D) double of the operating speed.
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70. The shaft of electric motors is generally supported in
(A) magnetic bearings
(B) bush bearings
(C) ball or roller bearings
(D) cast iron bearings.
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71. Ball and roller bearings are generally lubricated by
(A) graphite
(B) grease
(C) water
(D) air.
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Electric Machine Design PART 5
72. In case of ball bearings, the ball are made of
(A) cast iron
(B) mild steel
(C) carbon chrome steel
(D) none of the above.
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73. A ball bearing is secured to the shaft by means of
(A) key
(B) slot
(C) pin
(D) sleeve.
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74. In case of 110 MW generators, the shaft is supported on
(A) ball bearings
(B) roller bearing
(C) needle bearings
(D) bush bearings.
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Electric Machine Design PART 5
75. Which of the following is classed as anti friction bearing ?
(A) Ball bearing
(B) Roller bearing
(C) Needle bearing
(D) All of the above.
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