Electric Motors (21EE44)

Electric Motors

Course Code 21EE44 
CIE Marks 50
Teaching Hours/Week (L:T:P: S) 2:2:0 
SEE Marks 50
Total Hours of Pedagogy 40 Hours 
Total Marks 100
Credits 03 
Exam Hours 03

Module-1

DC Motors: Classification, Back emf, Torque equation, and significance of back emf, Characteristics of shunt, series & compound motors. Speed control of shunt, series and compound motors. Application of motors. DC motor starters – 3 point and 4 point. Losses and Efficiency- Losses in DC motors, power flow diagram, efficiency, condition for maximum efficiency

Module-2

Testing of DC Motors: Direct & indirect methods of testing of DC motors-Brake test, Swinburne’s test, Retardation test, Hopkinson’s test, Field’s test, merits and demerits of tests. Three Phase Induction Motors: Review of concept and generation of rotating magnetic field, Principle of operation, construction, classification and types; squirrel-cage, slip-ring (No question shall be set from the review portion). Slip, Torque equation, torque-slip characteristic covering motoring, generating and braking regions of operation, Maximum torque, significance of slip.

Module-3

Performance of Three-Phase Induction Motor: Phasor diagram of induction motor on no-load and on load, equivalent circuit, losses, efficiency, No-load and blocked rotor tests. Performance of the motor from the circle diagram and equivalent circuit. Cogging and crawling. High torque rotors-double cage and deep rotor bars. Equivalent circuit and performance evaluation of double cage induction motor. Induction motor working as induction generator.

Module-4

Starting and Speed Control of Three-Phase Induction Motors: Need for starter. Direct on line, Star-Delta, and autotransformer starting. Rotor resistance starting. Speed control by voltage, frequency, and rotor resistance methods Single-Phase Induction Motor: Double revolving field theory and principle of operation. Construction and operation of split-phase, capacitor start, capacitor run, and shaded pole motors. Comparison of single phase motors and applications.

Module-5

Synchronous Motor: Principle of operation, phasor diagrams, torque and torque angle, Blondel diagram, effect of change in load, effect of change in excitation, V and inverted V curves. Synchronous condenser, hunting and damping. Methods of starting synchronous motors. Other Motors: Construction and operation of Universal motor, AC servomotor, Linear induction motor, and stepper motors.

Suggested Learning Resources:

(1) Electric Machines, D. P. Kothari, I. J. Nagrath, McGraw Hill, 4th edition, 2011.

(2)Theory of Alternating Current Machines, Alexander Langsdorf, McGraw Hill, 2nd Edition, 2001.

(3) Electric Machines, Ashfaq Hussain, Dhanpat Rai & Co, 2nd Edition, 2013.

Activity Based Learning (Suggested Activities in Class)/ Practical Based learning

Activity and Practical Based learning, Quizzes.