ELECTRIC MOTORS (18EE44)

ELECTRIC MOTORS

Course Code 18EE44 CIE Marks 40
Number of Lecture Hours/Week  (L:T: 3:0:0 
SEE Marks 60
Credits 03 Exam Hours 03

Course Learning Objectives:

· To study the constructional features of Motors and select a suitable drive for specific application.
· To study the constructional features of Three Phase and Single phase induction Motors.
· To study different test to be conducted for the assessment of the performance characteristics of
motors.
· To study the speed control of motor by a different methods.
· Explain the construction and operation of Synchronous motor and special motors.

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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.

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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.

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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.

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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.

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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.

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Course Outcomes: At the end of the course the student will be able to:

· Explain the construction, operation and classification of DC Motor, AC motor and Special purpose
motors.
· Describe the performance characteristics & applications of Electric motors.
· Demonstrate and explain the methods of testing of DC machines and determine losses and
efficiency.
· Control the speed of DC motor and induction motor.
· Explain the starting methods, equivalent circuit and phasor diagrams, torque angle, effect of change
in excitation and change in load, hunting and damping of synchronous motors.

Question paper pattern:

· The question paper will have ten questions.
· Each full question is for 20 marks.
· There will be 2 full questions (with a maximum of three sub-questions in one full
question) from each module.
· Each full question with sub-questions will cover the contents under a module.
· Students will have to answer 5 full questions, selecting one full question from each module.

Text Books:

1 Electric Machines D. P. Kothari, I. J. Nagrat McGraw Hill 4th edition, 2011
2 Theory of Alternating CurrentMachines Alexand   Langsdorf
McGraw Hill 2nd Edition, 2001

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

Reference Books:

1 Electrical Machines, Drives and Power systems
Theodore Wildi Pearson 6th Edition, 2014 

2 Electrical Machines M.V. Deshpande PHI Learning 2013

3 Electric Machinery and   Transformers  Bhag S   Gur Oxford University   Press   3rd Edition, 2012
4 Electric Machinery and    Transformers   Irving Kosow Pearson 2rd Edition, 2012
5 Principles of Electric Machines    and    power Electronics   P.C.Sen Wiley 2nd Edition, 2013
6 Electric Machines R.K. Srivastava Cengage Learning 2nd Edition,2013