Generate maximum flux

Reduce the stray losses

Maintain the rotor speed constant

Produce more uniform rotor field and torque

Iron loss

Copper loss

Friction loss

Windage loss

By rotor rheostat control

By changing applied frequency

By changing the applied voltage

By changing the number of stator poles

To reduce the slip

To control the speed

To reduce the losses

To get high starting and running torque

Trip at over load

Switch ON at pre set time

Change from star to delta

Switch OFF at pre set time