Comparison of Squirrel Cage and Slip Ring Motor

 Comparison of Squirrel Cage and Slip Ring Motor

Rotor Construction

✓ Squirrel cage motor

Bars are used in rotor Squirrel cage motor is very simple, rugged and long lasting. No slip rings and brushes.

✓ Starting

Can be started by DOL star-delta

Do transformer starters

✓ Starting Torque

Low 

✓ Starting Current

High

✓ Speed variation

Not easy, but could be varied in large steps by pole changing or through smaller incremental steps through thyristors or by frequency variation.

✓ Maintenance

Almost Zero 

✓ Cost 

Low

Rotor Construction

✓ Slip ring motor

Winding wire is to be used.

Wound rotor required attention.

Slip ring and brushes are needed also need frequent maintenance.

✓ Starting

Rotor resistance arter is required.

✓ Starting Torque

Very High

✓ Starting Current

Low

✓ Speed variation

Easy to sary speed.

Speed change is possible by inserting rotor resistance using thyristors or by using frequency variation injecting emf in the rotor circuit cascading.

✓ Maintenance

Requires frequent maintenance

✓ Cost 

High