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.Management Sciences
Category: Synchronous Motors
A synchronous motor can be started by________?
A. pony motor
B. D.C. compound motor
C. providing damper winding
D. any of the above
When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected______________?
A. the motor stops
B. it runs as a reluctance motor at the same speed
C. it runs as a reluctance motor at a lower speed
D. none of the above
In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on___________?
A. load on the motor
B. d.c. excitation only
C. both the speed and rotor flux
D. none of the above
By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?
A. By changing the supply frequency
B. By interchanging any two phases
C. By changing the applied voltage
D. By changing the load
The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as__________?
A. locked-rotor torque
B. synchronous torque
C. pull up torque
D. reluctance torque
For V-curves for a synchronous motor the graph is drawn between:_______________?
A. armature current and power factor
B. terminal voltage and load factor
C. power factor and field current
D. field current and armature current
An over-excited synchronous motor takes__________?
A. leading current
B. lagging current
C. both A. and (b)
D. none of the above
The angle between the rotating stator flux and rotor poles is called _________ angle.
A. synchronizing
B. obtuse
C. torque
D. power factor
As the load is applied to a synchronous motor, the motor takes more armature current because
A. the increased load has to take more current
B. the rotor by shifting its phase backward causes motor to take more current
C. the back e.m.f. decreases causing an increase in motor current
D. the rotor strengthens the rotating field casuing more motor current
A pony motor is basically a_________?
A. small induction motor
B. D.C. series motor
C. D.C. shunt motor
D. double winding A.C./D.C. motor
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