| 1. | Slip rings are usually made of ? | |
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copper
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carbon
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phosphor bronze
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aluminium
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Report Question| 2. | In squirrel cage induction motors, the rotor slots are usually given slight skew in order to ? | |
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reduce windage losses
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reduce eddy currents
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reduce accumulation of dirt and dust
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reduce magnetic hum
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| 3. | 5 H.P., 50-Hz, 3-phase 40 V, induction motors are available for the following r.p.m. Which motor will be the costliest ? | |
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30 r.p.m
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960 r.p.m.
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440 r.p.m.
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2880 r.p.m.
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| 4. | The torque of a rotor in an induction motor under running condition is maximum ? | |
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at the unit value of slip
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at the zero value of slip
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at the value of the slip which makes rotor reactance per phase equal to the resistance per phase
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at the value of the slip which makes the rotor reactance half of the rotor resistance
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| 5. | In case of a double cage induction motor, the inner cage has ? | |
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high inductance and low resistance
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low inductance and high resistance
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low inductance and low resistance
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high inductance and high resistance
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| 6. | The starting torque of a 3-phase squirrel cage induction motor is ? | |
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twice the full load torque
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1.5 times the full load torque
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equal to full load torque
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None of the above
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| 7. | In the circle diagram for induction motor, the diameter of the circle represents ? | |
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Slip
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rotor current
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running torque
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line voltage
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| 8. | The efficiency of an induction motor can be expected to be nearly ? | |
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60 to 90%
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80 to 90%
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95 to 98%
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99%
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| 9. | An induction motor can run at synchronous speed when ? | |
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it is run on load
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it is run in reverse direction
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it is run on voltage higher than the rated voltage
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e.m.f. is injected in the rotor circuit
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| 10. | Two of the power supply terminals to a 3-phase induction motor get interchanged during reconnection after maintenance of the motor. When put back into service, the motor will ? | |
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get heated up and damaged
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rotate in the same direction as it was prior to maintenance
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fail to rotate
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rotate in the reverse direction to that prior to maintenance
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