# electric motors

Semester : IV

Course Code : 18EE44

CIE Marks : 40 SEE Marks : 60

## ELECTRIC MOTORS

18EE44

#### SYLLABUS

### 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 points and 4 points.**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, the significance of slip.

### Module-3

**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 an induction generator.

### Module-4

**Starting and Speed Control of Three-Phase Induction Motors:** Need for a 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 the 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, the effect of change in load, the 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