This set of Electrical Machines Interview Questions and Answers for freshers focuses 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
View Answer
Explanation: 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
View Answer
Explanation: 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?
a) 
b)
c)
d)
View Answer
Explanation: 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) 
b)
c)
d)
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: Any method mentioned will diminish the transients in the machine.
8. Employment of damper winding will reduce hunting.
a) True
b) False
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: It is zero.
14. When the rotor speed becomes greater than synchronous speed, which type of torque is produced in damper winding?
a) Induction generator
b) Synchronous generator
c) Reluctance motor
d) Induction motor
View Answer
Explanation: The slip will become negative and it will operate in generating mode.
15. When an alternator is loaded suddenly the torque produced in damper is?
a) Induction motor
b) Induction generator
c) Synchronous motor
d) Synchronous generator
View Answer
Explanation: Sudden loading will reduce the speed of the machine and so there will be small slip induced in the machine, making it operate as induction motor.
Sanfoundry Global Education & Learning Series – Electrical Machines.
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