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Free download in PDF Synchronous Motor Short Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams. These short solved questions or quizzes are provided by Gkseries.
41
In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
[A]
One-third
[B]
Twice
[C]
Thrice
[D]
Nine times
42
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
Answer: Changing frequency
43
The speed regulation of a synchronous motor is always
[A]
1%
[B]
0.5%
[C]
Positive
[D]
Zero
44
While running, a synchronous motor is compelled to run at synchronous speed because of
[A]
Damper winding in its pole faces
[B]
Magnetic locking between stator and rotor poles
[C]
Induced e.m.f. in rotor field winding by stator flux
[D]
Complusion due to Lenz's law
Answer: Magnetic locking between stator and rotor poles
45
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 (a) and (c)
46
In a synchronous motor, the rotor Cu losses are met by
[A]
Motor input
[B]
Armature input
[C]
Supply lines
[D]
D.C. source
47
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
48
The synchronous motor is not inherently self-starting because
[A]
The force required to accelerate the rotor to the synchronous speed in an instant is absent
[B]
The starting device to accelerate the rotor to near synchronous speed is absent
[C]
A rotating magnetic field does not have enough poles
[D]
The rotating magnetic field is produced by only 50 Hz frequency currents
Answer: The force required to accelerate the rotor to the synchronous speed in an instant is absent
49
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
Answer: None of the above
50
Synchronous motors are generally not self-starting because
[A]
The direction of rotation is not fixed
[B]
The direction of instantaneous torque reverse after half cycle
[C]
Startes cannot be used on these machiness
[D]
Starting winding is not provided on the machines
Answer: The direction of instantaneous torque reverse after half cycle
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