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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

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

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

116. In a synchronous motor, damper windings are provided on
A. stator frame
B. rotor shaft
C. pole faces
D. none of the above

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

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

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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