# Special Electrical Machines Fifth Sem

1. What are the types of synchronous reluctance motor?
2. What is a Vernier motor?
3. Mention any 3 applications of stepper motors.
4. What is slewing in a stepper motor?
5. Switched Reluctance motor is singly excited motor. Why?
6. What is the power rating of a normal switched reluctance motor?
7. What type of commutation is used in PMBL (permanent magnet
brush-less) D.C?
8. Write an equation for the e.m.f induced /ph of a square wave
PMBL D.C motor and explain each term in it.
9. What is the difference in stator windings between square wave
PMBL D.C motor and sine wave PMBL D.C motor?
10. How quasi-sinusoidal distribution of flux is achieved in a sine
wave PMBL D.C motor?
PART – B (5 x 12 = 60)
11. Explain the construction and principle of operation.
(i) Radial air gap cage less type synchronous reluctance motor.
(ii) Axial air gap cage less type synchronous reluctance motor.
(or)

12. With the help of a vector diagram explain the torque produced in
a synchronous reluctance motor.
13. Derive the expression for torque developed in a Variable
Reluctance type stepper motor and discuss the effect of
saturation.
(or)
14. Explain the static and dynamic characteristics of a stepper motor.
15. (a) Explain the differences between variable reluctance stepper
motor and switched reluctance motors.
(b) Explain the advantages and applications of switched
reluctance motors.
(or)
16. (a) Explain the hysteresis type of current regulator control circuit
for a switched reluctance motor.
(b) Explain the general torque-speed characteristics of a switched
reluctance motor.
17. (a) Draw the controller circuit for a PMBL square wave D.C
motor drive showing all the components.
(b) Explain the operation of the above controller circuit for a
PMBL square wave D.C motor drive.
(or)
18. Derive an expression for torque T in terms of T0, w and w0 for a
square wave PMBL D.C. motor.
19. Derive the expression for 3 Ph torque in a sine wave PMBL D.C
motor.
(or)
20. Draw and explain the torque – speed characteristics of a sine
wave PMBL D.C motor.