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Electrical Engineering Objective Questions { Synchronous Motors }

8. When excitation of a normally excited synchronous motor running with constant load s increased, it results in
A. increased Eb but decreased a
B. increased a and increased la
C. increased 1a and increased p.f.
D. increased a and increased p.f. angle

9. A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
A. power factor
B. torque angle
C. back emf
D. armature current

10. In a synchronous motor, damper winding is provided in order to
A. stabilize rotor motion
B. suppress rotor oscillations
C. develop necessary starting torque
D. both (b) and (c) above

11. In synchronous motor, the magnitude of stator back emf Vb depends on
A. speed of the motor
B. load on the motor
C. both the speed and rotor flux
D. dc excitation only

12. A synchronous motor is compelled to maintain synchronous speed because of
A. damper winding in its pole faces
B. magnetic backing between stator and rotor poles
C. induced emf in rotor field winding by stator flux
D. compulsion due to Lenz's law

13. The angle between synchronously rotating stator flux and rotor poles of a synchronous motor is called
A. synchronizing angle
B. torque angle
C. power factor angle
D. slip angle

14.  Synchronous motor can operate at
A. lagging power factor only
B. leading power factor only
C. unity power factor only
D. any of the above three

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