| 1. | Which of the following statements about 3-phase induction motor is incorrect ? | |
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It is capable of operation under a wide range of power factors both lagging and leading
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It starts up from rest and has not be synchronised
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Its no-load line current may be as large as 40% of the full load current
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It has no commutator and no slip rings
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Report Question| 2. | Slip rings for induction motors are made of ? | |
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phosphor bronze
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aluminium
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carbon
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cobalt steel
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| 3. | A 3-phase induction motor is running at a load of the rated torque. What happens when one of the outer mains is interrupted while the motor is running ? | |
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The motor keeps on running and the current drawn does not change
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The motor keeps on running but draws more current
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The motor stops immediately
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The motor stops after a few seconds
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| 4. | The starting torque of a squirrel-cage induction motor is ? | |
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low
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negligible
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same as full-load torque
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slightly more than full-load torque
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| 5. | In case of the induction motors the torque is ? | |
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inversely proportional to (?slip)
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directly proportional to (slip)2
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inversely proportional to slip
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directly proportional to slip
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| 6. | The auto-starters, (using three auto transformers) can be used to start cage induction motor of the following type ? | |
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star connected only
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delta connected only
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(a) and (b) both
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none of the above
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| 7. | Step less speed control of induction motor is possible by which of the following methods ? | |
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e.m.f. injection in rotor circuit
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changing the number of poles
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Cascade operation
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None of the above
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| 8. | In case of 3-phase induction motors, plugging means ? | |
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pulling the motor directly on line without a starter
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tocking of rotor due to harmonic
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starting the motor on load which is more than the rated load
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interchanging two supply phases for quick stopping
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| 9. | Which of the following component is usually fabricated out of silicon steel ? | |
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Bearings
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Shaft
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Stator core
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None of the above
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| 10. | In three-phase squirrel-cage induction motors ? | |
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rotor conductor ends are short circuited through slip rings
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rotor conductors are short-circuited through end rings
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rotor conductors are kept open
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rotor conductors are connected to insulation
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