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RAJAGIRI SCHOOL OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS
ELECTRICAL MACHINES III
E 701
Module III
1. Explain the principle of operation of an Induction Generator. Draw its phasor diagram.
Mention its advantages and disadvantages.
2. Mention the applications of Induction Generator.
3. Describe how an induction machine will behave as a generator when driven at above
the Synchronous speed.
4. Explain the Phasor diagram of an Induction Generator.
5. Explain the Torque – Speed Characteristics of an Induction Generator.
6. With necessary equations, explain the operation of an Induction generator.
7. Explain the construction and principle of operation of an induction generator with phasor
diagram and equivalent circuit.
8. What is a Synchronous Induction Motor?
9. Explain the construction, working and applications of Synchronous Induction Motor.
10. Briefly explain the action of Synchronous Induction Motor.
11. Describe the principle of operation of Synchronous Induction Motor.
12. Compare the performance of Synchronous Induction Motor with Synchronous and
Induction Motors.
13. Explain why Single-phase induction motors are not self-starting? What should be done
for making them self-starting?
14. Why is a Single-phase induction motor not self starting? Also describe any one method of
starting a Single-phase induction motor.
15. Explain how torque is produced in a Single phase split phase Induction Motor.
16. Draw the torque – slip characteristics of single phase Induction Motor and explain why it
is not self starting.
17. Describe the construction and operation of a single phase Induction Motor.
18. Explain how torque is produced in a Single Phase Induction Motor.
19. Explain the double field revolving theory applied to Single Phase Induction Motor.
20. Explain the principle of operation of single phase induction motor based on double field
revolving theory.
21. Explain the double revolving field theory for single-phase induction motors. Draw the
equivalent circuit.
22. On the basis of double field revolving theory, derive the equivalent circuit of single phase
induction motor.
23. Draw the Equivalent Circuit of a single phase Induction Motor under running conditions.
24. Draw the Equivalent Circuit of a single phase Induction Motor and explain how you will
determine the parameters of the equivalent circuit.
25. Describe with appropriate circuit diagrams the working of following types of single phase
Induction motors.
(a) Split phase (b) Capacitor Start © Shaded Pole
26. Draw the stator circuit diagram and the corresponding phasor diagram at starting for the
following types of single-phase induction motors.
(a) Capacitor start motor, (b) Capacitor start-capacitor run motor
27. Explain the construction and working principle of a capacitor start-capacitor run motor.
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28. Describe the construction and operation of a Shaded pole Motor.
29. Explain the Principle of Operation of a Shaded Pole Motor and mention its applications.
30. A 3-phase induction generator rated for 400 V, 50 Hz, 4 pole, 500kW is supplying a
400V grid, the generator being driven by a wind turbine. At a particular wind speed, the
generator supplies a real power of 100kW to the grid, the stator current being 200A.
What is the reactive power drawn from the grid? Sketch the system configuration,
indicating the wind turbine and the machine connected to the grid.
31. A 150kW, 400V, 50Hz, 4 pole, star connected induction machine is driven as an
induction generator supplying power to a three-phase, 400V, 50Hz grid. The rotor of the
generator is driven at 1560 r.p.m. The real power supplied to the grid is 100kW, at a
power factor of 0.707. What is the value of reactive power drawn from the grid? If the
magnetizing current drawn from the supply is 100A and if the generator works with an
efficiency of 95% for this load, estimate the generator rotor resistance in terms of stator.
Neglect core loss. Draw the phasor diagram of the generator indicating the stator current,
magnetizing current and rotor current, taking the stator phase voltage as the reference.
32. A 3-phase, 4-pole, star-connected, capacitor excited induction generator works with a
capacitor bank of 40µ F capacitor /phase connected in delta. The load is star-connected
with 10Ω resistance per phase. At a particular speed, the generator gives a terminal
voltage of 400 V, 50 Hz. Calculate (i) line current of the generator and (ii) power output
of the generator. Draw the circuit arrangement. The generator is driven by a wind turbine.
33. A 125W, 4 pole, 110V, 50 Hz, single-phase induction motor delivers rated output at a
slip of 6%. The total copper loss at full load is 25 W. Calculate the full load efficiency
and the rotor copper loss caused by the backward field. Rotational losses may be assumed
to be 25W. Neglect stator copper loss.
34. Calculate the parameters of the equivalent circuit of a capacitor start, single-phase, 230
V, 50 Hz, 4-pole, induction motor. The test result on the motor are as follows :
No-Load
: 230V
2.5A 120W
Blocked Rotor : 80V
6.0A
150W
The effective stator resistance is 2Ω. Calculate the motor output at a slip of 4%.
35. A 230V, 380W, 50 Hz, 4 pole, single phase Induction motor gave the following test
results.
No load test :
230V 84W 2.8A
Blocked Rotor test : 110V 460W 6.2 A
The stator winding resistance is 4.6 Ω and during the blocked rotor test, the auxiliary
winding is open. Determine the equivalent circuit parameters.
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