Basic Electrical and Electronics Engineering

8

Three-phase Induction Motors

TOPICS DISCUSSED

• Basic principle of a three-phase induction motor

• Constructional details

• Rotating magnetic field

• Synchronous speed

• Slip speed

• Rotor-equivalent circuit

• Rotor current

• Rotor frequency

• Power-flow diagram

• Torque

• Torque-slip characteristics

• Effect of change of rotor circuit resistance on torque-slip characteristics

• Starting torque

• Condition for maximum torque

• Starting

• Speed control

• Losses

• Efficiency

• Applications

8.1 Introduction

Three-phase induction motors are used in many industrial applications such as a drive motor. These motors are very rugged, and hence there is virtually no maintenance required. Only three-phase supply is required for the stator. No supply is to be provided to the rotor. ...