Question Paper Code : 50977
B.E./B.Tech. DEGREE EXAMINATIONS, APRIL/MAY 2024.
Fifth/Sixth Semester
Electrical and Electronics Engineering
EE 3009 — SPECIAL ELECTRICAL MACHINES
(Common to : )
(Regulations 2021)
Answer ALL questions.
PART A — (10 × 2 = 20 marks)
- 1.
Name two types of stepper motors.
- 2.
Write the concept of closed-loop control in stepper motor drives.
- 3.
What are the power controllers used in SRM drives?
- 4.
Write the principle of torque prediction in SRMs.
- 5.
Name two types of permanent magnets used in PMBLDC motors.
- 6.
Write the emf equation of PMBLDC motors.
- 7.
What are the machine configurations of PMSMs?
- 8.
List four general types of rotors in permanent magnet synchronous machines.
- 9.
Name the applications of hysteresis motors.
- 10.
What is hysteresis power loss in hysteresis motor?
PART B — (5 × 13 = 65 marks)
- 11.(a)
Explain the constructional features and operation principle of stepper motors.
- Or
- (b)
Describe the drive circuits used in stepper motor control and their significance in different applications.
- 12.(a)
Explain the methods for speed and current control in SRM drives.
- Or
- (b)
Discuss on rotor position measurement and estimation methods of SRM drives.
- 13.(a)
Explain the principle of operation of PMBLDC motors and analyze the magnetic circuit.
- Or
- (b)
Discuss the current and speed controllers in PMBLDC motor drives.
- 14.(a)
Describe the torque-speed characteristics of PMSMs.
- Or
- (b)
Describe the operating principle and characteristics of synchronous reluctance motors.
- 15.(a)
Discuss the principle of operation and characteristics of hysteresis.
- Or
- (b)
Compare and contrast the characteristics of hystersis motors, AC series motors, and linear motors.
PART C — (1 × 15 = 15 marks)
- 16.(a)
Design a closed-loop control system for a stepper motor-driven robotic arm, considering torque predictions.
- Or
- (b)
A three phase, Y-connected, 2p = 6 pole, PM brushless motor has the surface PM of inner radius R_in = 0.06m, outer radius R_out = 0.11m and the pole shoe width-to-pole pitch ratio alpha = 0.84, the number of turns per phase N_1 = 222, the winding factor k_w1 = 0.926 and the peak value of the air gap magnetic flux density B_mg = 0.65T. Neglecting the armature reaction, find approximate values of the EMF, electromagentic torque developed by the motor and electromagnetic power at 1200 rpm and rms current I_a = 13.6A for 120 degree square wave operation.