1. Which of the following type of induction motor can use to drive high inertia load?
(a) slip ring type.
(b) squirrel cage type.
(c) Single phase induction motor.
(d) none of the above. Answer
2. In a squirrel cage motor the induced e.m.f. is
(a) dependent on the shaft loading.
(b) dependent on the number of slots.
(c) slip times the stand still e.m.f. induced in the rotor.
(d) none of the above. Answer
3. Slip ring motor is preferred over squirrel cage induction motor where
(a) high starting torque is required.
(b) load torque is heavy.
(c) heavy pull out torque is required.
(d) all of the above. Answer
4. The torque of an induction motor is
(a) directly proportional to slip.
(b) inversely proportional to slip.
(c) proportional to the square of the slip.
(d) none of the above. Answer
5. In three-phase induction motors sometimes copper bars are placed deep in the rotor to
(a) improve starting torque.
(b) reduce copper losses.
(c) improve efficiency.
(d) improve power factor. Answer
6. The starting torque of a single phase squirrel-cage motor
(a) is low.
(b) is high.
(c) depends on load.
(d) depends on rotor current. Answer
7. The power scale of circle diagram of an induction motor can be found from
(a) stator resistance test.
(b) no-load test only.
(c) short-circuit test only.
(d) noue of the above. Answer
8. A change of 4% of supply voltage to an induction motor will produce a change of approximately
(a) 4% in the rotor torque.
(b) 8% in the rotor torque.
(c) 12% in the rotor torque.
(d) 16% in the rotor torque. Answer
9. The stating torque of the slip ring induction motor can be increased by adding
(a) external inductance to the rotor.
(b) external resistance to the rotor.
(c) external capacitance to the rotor.
(d) both resistance and inductance to rotor. Answer
10. Which one of the following can not be determine by circle diagram for an induction motor?
(a) power factor.
(b) efficiency.
(c) frequency.
(d) output. Answer
11. Blocked rotor test on induction motors can be used to determine
(a) efficiency.
(b) leakage reactance.
(c) rotor reactance.
(d) all of the above. Answer
12. An induction motor can run at synchronous speed when
(a) it is over excited.
(b) e.m.f. is injected in the rotor circuit.
(c) it is run in reverse direction.
(d) it is run on voltage higher than the rated voltage. Answer
13. It is advisable to avoid line-starting of induction motor and use starter because
(a) motor takes five to seven times its full load current.
(b) it will pick-up very high speed and may go out of step.
(c) it will run in reverse direction.
(d) starting torque is very high. Answer
14. Which of the following method can be used for stepless speed control of induction motor ?
(a) e.m.f. injection in rotor circuit.
(b) Changing the number of poles.
(c) Cascade operation.
(d) None of the above. Answer
15. Rotor rheostat control method of speed control is used for
(a) squirrel-cage induction motors only.
(b) slip ring induction motors only.
(c) both squirrel-cage and slip ring induction motor.
(d) none of the above. Answer
« BACK NEXT »