| 1. | Hunting in a synchronous motor cannot be due to ? | |
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windage friction
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variable load
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variable frequency
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variable supply voltage
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Report Question| 2. | The duration of sudden snort-circuit test on a synchronous motor is usually about ? | |
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one hour
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one minute
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one second
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none of the above
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| 3. | The maximum power developed in a synchronous motor will depend on ? | |
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the rotor excitation only
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the supply voltage only
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the rotor excitation and supply voltage both
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the rotor excitation, supply voltage and maximum value of coupling angle (90º)
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| 4. | The size of a synchronous motor decreases with the increase in ? | |
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flux density
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horse power rating
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speed
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all of the above
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| 5. | ln a synchronous motor, the damping winding is generally used to ? | |
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prevent hunting and provide the starting torque
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reduce the eddy currents
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provide starting torque only
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reduces noise level
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| 6. | The maximum speed variation in a 3 phase synchronous motor is ? | |
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10 per cent
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6 per cent
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4 per cent
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zero
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| 7. | If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor ? | |
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will become more
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will become less
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will remain unchanged
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none of the above
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| 8. | While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerating torque is produced by ? | |
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induction motor torque in field winding
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induction motor torque in damper winding
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eddy current and hysteresis torque in pole faces
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all of the above methods
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| 9. | If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor ? | |
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become more
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become less
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remain constant
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none of the above
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| 10. | When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during bunting, the damper bars develop ? | |
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inductor motor torque
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induction generator torque
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synchronous motor torque
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d.c. motor torque
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