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Electrical Engineering Objective Questions { Synchronous Motors }



85. When the voltage applied to a synchronous motor is increased, which of the following will reduce?
A. Stator flux
B. Pull in torque
C. Both (a) and (b)
D. None of the above

86. The speed of the synchronous motor
A. increases with increase in load
B. decreases as load increases
C. varies with power factor
D. always remains constant

87. Dust and dirt accumulation on motor winding will result in
A. rise in winding temperature
B. increased core losses
C. shorting of coils
D. eddy current flow

88. The efficiency of a properly desiged synchronous motor will usually fall in range
A. 60 to 70%
B. 75 to 80%
C. 85 to 95%
D. 99 to 99.5%

89. To limit the operating temperature an electrical machine should have proper
A. voltage rating
B. current rating
C. power factor
D. speed

90.  Slip-rings in a synchronous motor carry
A. direct current
B. alternating current
C. no current
D. all of the above

91. A synchronous machine with large air gap has
A. a higher value of stability limit
B. a small value of inherent regulation
C. a higher synchronizing power which makes the machine less sensitive to load variations
D. all of the above

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