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Guru Tegh Bahadur Institute of Technology
Department of Electrical and Electronics Engineering
Semester - 7
Electric Drives Laboratory- ETEE – 451
Question Bank
1. Define Electric Drives in two words.
2. What are types of Electric Drives based on the prime-movers.
3. Give an example of a power modulator.
4. Which is the most rugged machine?
5. Convert a) Fix Vac ------- Variable Vdc using two methods.
6. How do you get variable frequency & voltage from fixed frequency & voltage?
7. In aircraft/space equipments, _________ is increased to _______ Hz to increased
power/weight ratio.
8. Explain hoist operation:-a. Loaded cage to be taken up against weight.
b. Empty cage to be taken up against free upwards.
c. Empty cage to be taken down against free upwards.
d. Loaded cage to be taken down against free down movement.
9. Give the type of load torque for
a. Fan, centrifugal pump, compressor, ship propeller.
10. What are active load torques?
11. What are passive load torques?
12. Where is a DC shunt motor used?
13. Where is a DC series motor used?
14. Where is a compound motor used?
15. Give regenerative braking characteristic of a separately excited motor.
16. Why regenerative braking is not possible in series motor?
17. What is dynamic braking?
18. Give equivalent circuit diagram for regenerative braking in a series motor.
19. Give plugging connection for separately excited and series motor.
20. Give output voltage waveform of single phase full controlled rectifier.
Faculty: Harshpreet Kaur and Kavita Jha
21. Give the waveform for discontinuous condition.
22. Give the waveform for continuous condition.
23. In which quadrant does the Fully Controlled Rectifier work? Draw connection
diagram.
24. Draw speed-torque characteristics for the above.
25. Draw chopper circuit for motor control.
26. Draw chopper circuit for regenerative braking control?
27. Draw chopper circuit for combined forward motoring and braking?
28. Draw speed-torque characteristics for series motor – chopper control.
29. Explain closed loop control scheme for above & below base speed control of DC
motor.
30. What are methods of speed control for induction motor?
31. At  ms (synchronous speed), what is the value of torque and rotor current?
32. At zero motor speed, what is the value of torque and rotor current?
33. How do you reverse the direction of rotating field in the induction motor?
34. What are the advantages of deep bar & double cage in an induction motor?
35. What are high slip Induction Motors?
36. What is Torque motor?
37. Give phasor diagram of an induction motor?
38. What is starting current in an Induction Motor?
39. Phasor diagram
40. Explain braking – regenerative and plugging.
41. Give plugging speed-torque characteristics for an induction motor.
42. Explain plugging for active load driving the motor in opposite direction.
43. Give the quadrants of motor operation in which plugging takes place.
44. How do you control armature voltage of an Induction motor. (Power electronic
converter).
45. Why is V/f control used for speed control of Induction Motor?
46. What is the range of speed control with V/f control?
47. Give speed-torque & V-f characteristics for V/f control.
48. Show constant Power & constant torque modes.
Faculty: Harshpreet Kaur and Kavita Jha
49. Arrange MOSFET/Thyristor/IGBT/GTO in order of increasing power rating.
50. What are the preferable firing angle ranges for different experiment kits in the
lab?
51. What are motor ratings for different experiment kits in the lab?
52. What are different Power Electronic converters used for different experiments in
the lab?
53. What is the load range for which AC voltage control method can be used for
induction motor speed control?
54. What is type of load for which it is suitable?
55. What is the limitation of cycloconverter control?
56. Cycloconverter is used in low/high power drives?
57. Out of CSI & VSI, which is reliable for low cost/multi-motor drives?
58. In a CL control, is V signal (flux control block for VSI & CSI control) generated
from f or f from V why___?
Faculty: Harshpreet Kaur and Kavita Jha