B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.
Seventh Semester
Electrical and Electronics Engineering
EE 2403 — SPECIAL ELECTRICAL MACHINES
(Regulation 2008)
Time : Three hours Maximum : 100 marks
PART A — (10 × 2 = 20 marks)
1. Write voltage and torque equations of a synchronous reluctance motor.
2. Define reluctance torque.
3. Draw the block diagram of the drive systems of s stepping motor.
4. What is meant by hybrid stepping motors?
5. Explain why rotor position sensor is essential for the operations of SRM.
6. State the applications of switched reluctance motors.
7. How are the directions of rotations reversed in case of PLBLDC motor?
8. What is electronic commutator?
9. Write down the expressions for the self and synchronous reactance of permanent magnet synchronous motor.
10. List a few applications of PMSM.
PART B — (5 × 16 = 80 marks)
11. (a) Describe the constructional features of synchronous reluctance motor and explain its characteristics. Also draw the phasor diagram.
Or
(b) Differentiate between axial and radial air gap synchronous reluctance motors. Compare the performance of synchronous reluctance motor with switched reluctance motor.
12. (a) Discuss the principle of operations of permanent magnet stepper motor with torque Vs angle characteristics.
Or
(b) Discuss dual voltage driver circuit for two phase on drive of a four phase stepper motor and explain the nature of current build up in dual voltage drive.
13. (a) Discuss the various converter topologies for a 3 phase switched reluctance motor with merits and demerits of each. Explain any two of them.

Or
(b) With a neat block diagram, describe in detail the microprocessor based controller in switched reluctance motor.
14. (a) Sketch the structure of controller for PMBL DC motor and explain the functions of various blocks.
Or
(b) (i) Distinguish between mechanical and electronic commutators. (8)
(ii) Draw the diagram of electronic commutator. Explain the operation of the same. (8)
15. (a) Derive the expression for power input and torque of a PMSM. Explain how its torque speed characteristics are obtained.
Or
(b) Describe in detail the vector control of PMSM.