Hall Ticket No Question Paper Code: BPE003
INSTITUTE OF AERONAUTICAL ENGINEERING
(Autonomous)
M.Tech I Semester End Examinations (Regular) February, 2017
Regulation: IARE-R16
SPECIAL MACHINES AND CONTROLLERS
(Power Electronics and Electric Drives)
Time: 3 Hours Max Marks: 70
Answer ONE Question from each Unit
All Questions Carry Equal Marks
All parts of the question must be answered in one place only
UNIT I
1. Describe the constructional features of axial and radial flux synchronous reluctance motor with
their operating characteristics.
Derive the voltage and torque equations of synchronous reluctance motor.

2. Differentiate between axial and radial air gap synchronous motors. Compare the performance of
synchronous reluctance motor with switched reluctance motor
Draw and discuss the torque speed characteristics of synchronous reluctance motor.
Explain in detail the construction and operation of Vernier motor and draw its phasor diagram.

UNIT II
3. A 3-phase, 3 stack variable reluctance stepper motor has 20 poles on each rotor and stator stack.
Compute the step angle of the stepper motor. Assume double layer winding.
Discuss the static and dynamic characteristics of stepper motor with a neat diagram.
4. Discuss the dual voltage driver circuit for phase on drive of a 4 phase stepper motor and
explain the nature of current build up in dual drive.
Explain the constructional features and operation of a hybrid motor.
Describe step position error and holding torque resulting from load torque TL. Draw the torqueangle
curve.
UNIT III
5. Illustrate the various modes of operation of switched reluctance motor with relevant plots.[7M]
With a neat block diagram explain the closed loop speed control of a switched reluctance motor.

6. Enumerate the procedure for the prediction of torque and control mechanism with relevant voltage
and flux waveforms for switched reluctance motor in single pulse mode.
Discuss the various converter topologies for a 3-phase switched reluctance motor with merits and
de-merits.
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UNIT IV
7. Draw and explain the operation of electronic commutators.
Derive the torque and emf equations of a permanent magnet brushless DC motor.
8. Explain the magnetic circuit analysis of brushless DC motor on open circuit.
Sketch the structure of controller for PMBLDC motor and explain the functions of various blocks.

UNIT V
9. Derive the expression for power input and torque of a permanent magnet synchronous motor.
Explain how its torque speed characteristics are obtained?
Draw the equivalent circuit and vector diagram of a permanent magnet synchronous motor with
relevant voltage equations and flux linkage components.
10. Explain how a smooth torque is ensured in a permanent magnet synchronous motor. Draw the
phasor diagram corresponding to leading power factor operation.
Discuss the different current control schemes in permanent magnet synchronous motor and mention
the effects of demagnetizing mmf.
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