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Electrical Engineering Objective Questions { Synchronous Motors }

113. Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current?
A. High field current
B. Low short cirucit ratio
C. High core losses
D. Low field current
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114. In a synchronous motor, the maximum power developed depends on all of the following except
A. rotor excitation
B. maximum value of coupling angle
C. direction of rotating
D. supply voltage
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115. In a 3-phase synchronous motor, the negative phase sequence exists when the motor is
A. supplied with unbalanced voltage
B. under-loaded
C. over-loaded
D. none of the above
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116. In a synchronous motor, damper windings are provided on
A. stator frame
B. rotor shaft
C. pole faces
D. none of the above
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117. The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as
A. pull-up torque
B. pull-in torque
C. pull-out torque
D. none of the above
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118. A synchronous machine with low value of short-circuit ratio has
A. lower stability limit
B. high stability limit
C. good speed regulation
D. good voltage regulation
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119. Exciters of synchronous machines are
A. d.c. shunt machines
B. d.c. series machines
C. d.c. compound machines
D. any of the above
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