**Anna University**

**Department of Electrical and Electronics Engineering**

**EE2352 Solid State Drives**

**Important Questions - 2013**

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**UNIT I **

1. Derive the mathematical condition for steady state stability.

2. Briefly explain about the four quadrant operation of electric drive. (Or) Explain in detail about multi quadrant operation of low speed hoist drive with neat diagram.

3. (a) Explain about all three modes of operation of electric drive.

(b) Briefly explain about types of braking of electric drive. **4. **(i) Briefly analyze the load torque characteristics for all types of load.

(ii) Explain about the different classes of motor duty.

(iii) Explain about load equalization and derive the expression for moment of inertia of flywheel.

5. Describe the torque equation governing the motor load dynamics.

UNIT **II **6. Describe the operation of single phase fully controlled rectifier control of separately excited DC motor and obtain the expression for motor speed for continuous and discontinuous modes of operations.

7. Explain the motoring and braking operation of three phase fully controlled rectifier control of DC separately excited motor with aid of diagrams and waveforms(for a = 30°, 600

**,**90°, 120°, 150°, 180°). Also obtain the expression for motor terminal voltage and speed.

8. (i) Explain in detail about CLC and TRC methods.

(ii) Explain about the Ward —Leonard method of speed control of DC motor.

**9.**Explain the operation of four quadrant DC chopper.

**10.**Explain the operation of a two quadrant chopper fed DC drives.

UNIT **III 11. **Derive the transfer function of separately excited DC motor and load.

12. Explain in detail about design of speed controller and current controller. (Or) Describe the closed loop speed control of separately excited DC motor by proportional controller. (Or) Explain the current limit control of separately excited DC motor.

13. Write short notes on : (i) Field weakening mode control, (ii) Armature voltage control

**14.**Explain in detail about converter selection and characteristics?

15. Explain in detail the use of simulation software packages with flowchart.

**UNIT IV **16. Explain in detail about Vector control of induction motor drive.

17. (i) Explain the operation of constant air gap flux control.

(ii) Explain the operation of constant slip speed control.

18. Explain the induction motor operation when the V / f ratio is held constant also derive the expression for maximum torque?

19. Draw and explain the slip power recovery scheme applicable for three phase slip- ring induction motor.

20. Using a diagram and speed- torque curve, explain the stator voltage control scheme for the speed control of a three phase induction motor.

**UNIT V**

21. (i) Explain with the block diagram of marginal angle control of synchronous motor drive.

(ii) Explain Power factor control of synchronous drive.

22. (i) Describe the self control of synchronous motor.

(ii) Explain the operation of open loop (V/f) control / separate control of multiple synchronous motors with Schematic diagram?

23. Explain the closed loop control system of adjustable speed synchronous motor drives.

24. Explain the construction and operation of permanent magnet synchronous motor.

25. Explain how three phase synchronous motor fed by a three phase inverter can be made to behave like a simple DC motor. Hence is it proper to call them as a commutator less DC motor. (Or) Explain in detail about the brushless DC motor drive.