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Electrical Engineering Objective Questions { Synchronous Motors }



64. A synchronous motor can be made self starting by providing
A. damper winding on rotor poles
B. damper winding on stator
C. damper winding on stator as well as rotor poles
D. none of the above
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65.  The oscillations in a synchronous motor can be damped out by
A. maintaining constant excitation
B. running the motor on leading power factors
C. providing damper bars in the rotor pole faces
D. oscillations cannot be damped
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66. When the field of a synchronous motor is under-excited, the power factor will be
A. leading
B. lagging
C. unity
D. zero
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67. The speed regulation of a synchronous motor is always
A.1%
B.0.50%
C. positive
D. zero
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68. The percentage slip in case of a synchronous motor is
A.1%
B.100%
C.0.50%
D. zero
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69. 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
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70. A synchronous motor will always stop when
A. supply voltage fluctuates
B. load in motor varies
C. excitation winding gets disconnected
D. supply voltage frequency changes
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