Electrical Machines Interview Questions and Answers for freshers on “Hunting and Damper Windings”.
1. The relative speed between rotor and stator field is zero. This means ___________
A. mechanical speed of rotor is equal to stator field speed
B. mechanical speed is zero
C. stator field is stationary
D. none of the mentioned
Answer: A
Clarification: The relative speed is between the rotor and the stator field.
2. The satisfactory operation of the synchronous machine means ___________
A. mechanical speed of rotor is equal to stator field speed
B. mechanical speed is zero
C. stator field is stationary
D. none of the mentioned
Answer: A
Clarification: The relative speed should be zero between the rotor and the stator field.
3. Variation of load angle delta, after sudden loading of an unloaded synchronous motor with no damping is?
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B.electrical-machines-interview-questions-answers-freshers-q3b”>
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Answer: A
Clarification: With no damping there will be oscillations in the rotor angle.
4. Variation of load angle delta, with loading of an unloaded synchronous motor with damping is?
A. electrical-machines-interview-questions-answers-freshers-q4a”>
B. electrical-machines-interview-questions-answers-freshers-q3a”>
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D. electrical-machines-interview-questions-answers-freshers-q3d”>
Answer: A
Clarification: With damping the load angle damps out to nominal value.
5. Effects of hunting are/is ___________
A. mechanical stress
B. surge in current
C. rise in temperature
D. all of the mentioned
Answer: D
Clarification: Hunting causes all the mentioned effects on the synchronous machine.
6. What are the probable causes of hunting?
A. sudden change in load
B. fault in supply
C. sudden change in field current
D. all of the mentioned
Answer: D
Clarification: Changing the load suddenly, excitation or the faults will cause transients in the machine.
7. Using a _____ can be used to limit hunting.
A. Flywheel
B. DC Exciter
C. Large load
D. Any of the mentioned
Answer: D
Clarification: Any method mentioned will diminish the transients in the machine.
8. Employment of damper winding will reduce hunting.
A. True
B. False
Answer: A
Clarification: Damper winding are mechanical windings which also reduce the hunting.
9. Damper windings are made of ___________
A. copper
B. iron
C. silicon
D. cast iron
Answer: A
Clarification: They are made of copper as the current also flows through them.
10. The damper winding are placed in ___________
A. pole shoes
B. series with armature
C. series with field
D. rotor slots
Answer: A
Clarification: The damper winding are placed in pole shoes.
11. Turbo generators do not use damper winding due to ___________
A. solid steel rotor core
B. laminated armature
C. soft iron core
D. small current flow in pole shoes
Answer: A
Clarification: Because eddy current in the q-axis produce the same effect as the damper in salient pole machine.
12. Damper winding should have ___________
A. high resistance
B. low starting torque
C. low resistance
D. low reactance
Answer: C
Clarification: For desired hunting, the damper winding should have low resistance.
13. At synchronous speed, relative speed between rotating air-gap flux and damper is?
A. zero
B. Ns
C. lesser than Ns
D. more than zero