Dr. Mahalingam College of Engineering and Technology, Pollachi-3

Dr. Mahalingam College of Engineering and Technology, Pollachi-3

(An Autonomous Institution affiliated to Anna University)

CCET-III/(2011 Regulation)

Course CodeCourse Title:11EE914SPECIAL ELECTRICAL MACHINES

Name of Programme:B.E & EEE

Sem:VIIIDate&Session:01.02.2017&AN1Duration: 1½ hours Max. Marks: 40

Part- A Objective Questions (10X1=10 Marks)
Q. No / Question / CO No / Blooms Level
1 / Maximum torque developed by stepper motor for the given stepping rate in the start-stop mode of operation without losing synchronism is called ______
(a)Pull in range (b) Pull out range
(c) Pull in torque (d) Pull out torque / 2 / U
2 / The torque generated in permanent magnet stepper motor is due to ______
(a)Faradays law of Electromagnetic induction (b) Faradays law of Electromagnetic interaction
(c) Reluctance torque
(d) Pull out torque / 2 / R
3 / A Switched Reluctance motor differs from a VR stepper motor in the sense that it
(a) Has rotor poles of ferromagnetic material
(b) Rotate continuously
(c)Is designed for open loop operation only
(d) Rotate discontinuously / 3 / U
4 / Switched Reluctance motor configurations depends on
(a) Number of stator/rotor poles
(b) Number of phases
(c) Number of repetitions
(d) Number of slots / 3 / U
5 / Switched reluctance motor Torque is independent of the direction of ______
a) voltage b) current c) resistance d) inductance / 3 / U
6 / Torque equation of PMBLDC motor is ______
(a) 2 Bg rl ωmTph (b) Bg rl ωmTph
(c) 4 Bg rl ωmTph (d) 1.11 Bg rl ωmTph / 4 / R
7 / A commutator in a d.c. machine ______
(a) Reduces power loss in armature.
(b) Reduces power loss in field circuit.
(c) Converts the induced a.c armature voltage into direct
voltage.
(d) Is not necessary / 4 / U
8 / Permeance coefficient is ______/ 4 / R
9 / Relation between electrical angular velocity and mechanical angular velocity is
(a)Wm= We/P (b) We=PWm
(c)We=Wm/P (d) None of these / 5 / R
10 / Speed of permanent magnet synchronous motor is ______
(a) 120f/P (b) P/120 f (c) P/60 f (d) 120/Pf / 5 / R
Part- B Short Answer Questions (5X2=10 Marks)
Q. No / Question / CO No / Blooms Level
11 / A stepper motor has 8 poles in stator, 4 poles in rotor and finds its resolution. / 2 / Ap
12 / What is the necessity of current control circuit for SRM? / 3 / U
13 / What is the need for shaft position sensor for SRM? / 3 / U
14 / Why the PMBLDC motor is called electronically commutated motor? / 4 / U
15 / Draw the torque –speed characteristics of PM sine wave motor. / 5 / R
Part- C Descriptive – either or questions (2X10=20 Marks)
Q. No / Question / CO No / Blooms Level
16. (a) / Explain Microprocessor control of stepping motors with block diagram / 2 / U
OR
16.(b) / With neat diagram explain the sensor less operation of SRM / 3 / U
17. (a) / Draw the IGBT based inverter circuit for the delta connected PMBLDC motor and sketch the firing sequence and phase current waveform for 120 degree mode. / 4 / U
OR
17.(b) / Derive the emf and torque equation of permanent magnet sine wave motor. / 5 / U

Note:

Code for Blooms Levels:

Sl.
No. / Blooms Level / Code
1 / Remember / R
2 / Understand / U
3 / Apply / Ap
4 / Analyze / An
5 / Evaluate / E
6 / Create / C

Signature of the Faculty