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.Management Sciences
Category: Synchronous Motors
When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor___________?
A. remains same as the original value
B. decreases to half the original value
C. tends to becomes zero
D. increases to two times the original value
The armature current of the synchronous motor has higher values for_____________?
A. high excitation only
B. low excitation only
C. both A. and (b)
D. none of the above
Slip-rings in a synchronous motor carry____________?
A. direct current
B. alternating current
C. no current
D. all of the above
A synchronous motor running with normal excitation adjusts to load increases essentially by increase in______________?
A. back e.m.f.
B. armature current
C. power factor
D. torque angle
The operating speed of a synchronous motor can be changed to new fixed value by___________?
A. changing the load
B. changing the supply voltage
C. changing frequency
D. using brakes
The duration of sudden snort-circuit test on a synchronous motor is usually about_____________?
A. one hour
B. one minute
C. one second
D. none of the above
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 rotation
D. supply voltage
A synchronous motor can operate at____________?
A. lagging power factor only
B. leading power factor only
C. unity power factor only
D. lagging, leading and unity power factors
If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then_____________?
A. the stator current will be zero
B. the stator current will be very small
C. the stator current will be very high
D. the back e.m.f. will be more than the supply voltage
E. none of the above
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