B.E/B.Tech Degree Examination November/December 2010, 
Seventh Semester,                                           Electrical and Electronics Engineering, 
                                EE1001-SPECIAL ELECTRICAL MACHINES
Answer all the questions.



1. Compare synchronous reluctance motor with Switched reluctance motor.
2. Why the power factor of Synchronous reluctance motor is much lower than Permanent magnet motor?
3. Write down the equation for step angle of stepper motor.
4. Draw the equivalent circuit of a winding in a stepper motor.
5. Differentiate Variable reluctance stepper motor with Switched reluctance motor.
6. Define Energy ratio.
7. What is PMBLDC machine?
8. What is electronic commutator?
9. Draw the torque-speed characteristics of PMSM.
10. Define Synchronous reluctance.


11.(a) Derive the open circuit emf of Synchronous reluctance motor. (16)
11.(b)(i) Explain the steady state phasor diagram of Synchronous motor. (8)
(ii) Derive the expression for d-axis synchronous reactance of a permanent magnet Synchronous reluctance motor. (8)

12.(a) Explain the modes of excitation of a stepper motor with neat diagram. (16)
12.(b) With a neat sketch, explain the different types of Logic sequencers for a stepper motor. (16)

13.(a)(i)Derive the torque expression for Switched reluctance motor. (8)
(ii)Explain the non linear analysis of SRM. (8)
13.(b)(i) Explain the role of microprocessors in control of switched reluctance motor. (8)
(ii) Explain the speed-torque characteristics of SRM. (8)

14.(a)(i) Prove that the torque equation in BLDC motor is similar to that of dc motor. (10)
(ii) Compare electronic commutator and mechanical commutator. (6)
14. (b)(i) Derive the equation for permeance coefficient (PC) of BLDC motor. (6)
(ii) Explain the construction and principle of operation of PMBLDC with neat diagram. (10)

15. (a)(i) Derive self and mutual inductance of Permanent magnet synchronous motor. (10)
(ii) Compare the volt-ampere and torque/ampere of a BLDC with PMSM. (6)
15. (b) With a neat sketch, explain the microprocessor based speed control of PMSM. (16)