Electrical Machines Mock Test 8

1. Number of the slip rings required for the satisfied operation of an induction motor is?

2. A 10kW,400V, 4-pole delta connected induction motor gave the following test results:

No-load test: 400V, 8A, 250 W
Blocked rotor test: 90V, 35A, 1350 W

The dc resistance per phase is 0.6 ohms. The no load rotational losses is?

3. No load power factor of the induction motor will __________ if the no load test is conducted at its rated frequency but less than the rated voltage.

4. If the no load test is conducted at its rated frequency but less than the rated voltage, then the mechanical losses will _____ and the constant losses will _________

5. Auto transformer method of starting has most acceptable method for the starting of the induction motor due to __________

6. The phasor diagram for the induction generator is best represented by?

7. If the frequency is reduced by 50% for a 3-phase, 50 Hz induction motor having 4 poles. The slip at which the maximum torque occurs becomes _________

8. Which of the following will not happen if one of the phases to the induction motor is not available?

9. I. An induction can never operate at leading power factor.
II. Speed of the induction motor can be made more than synchronous speed and still it will work as motor.

10. In a 3-phase induction generator which is self excited, load has been increased. To keep the frequency of the generated voltage constant, speed of the induction machine should be _________