Slip Ring vs Squirrel Cage Induction Motor

Slip Ring & Squirrel Cage Induction Motor

The squirrel cage induction motor is the most popular type of AC motor. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. The slip ring motor has very little application in industries. Rarely 5% – 10% slip ring motors are used in industries because it has several disadvantages like it required frequent maintenance, having a high copper loss, etc.

One of the major difference between the slip ring and the squirrel cage motor is that the slip ring motor has an external resistance circuit for controlling the speed of the motor. Whereas in squirrel cage motor, it is not possible to add any external circuit because the bar of the motor is permanently shorted at the end of the ring. Some other differences between them are explained below in the comparison chart.

Key Differences Between Slip Ring & Squirrel Cage Induction Motor

• The motor whose rotor is wound type such type of motor is called slip ring induction motor, whereas the squirrel cage motor, has a squirrel cage type rotor.
• The rotor of the slip ring motor has a cylindrical core with parallel slots, and each slot consists each bar. The slot of the squirrel cage motor is not parallel to each other.
• The slip ring motor is also called phase wound rotor. The another name of the squirrel cage motor is cage motor.
• The construction of the slip-ring motor is complicated because it consists slip ring and brushes whereas the construction of the squirrel cage motor is simple.
• The phase wound motor consists external resistance circuit, whereas in squirrel cage motor it is not possible to add any external resistance circuit because their rotor bars are permanently slotted.
• For starting the slip ring motor the rotor resistance starter is used, whereas the slip ring motor does not require any starter.
• The starting torque of the slip-ring motor is high, whereas in squirrel cage motor it is low.
• The maintenance cost of the slip ring motor is high as compared to squirrel cage motor because the slip ring motor consists brushes and rings.
• The copper loss is more in slip ring motor as compared to squirrel cage motor.
• The slip ring motor has brushes for transferring the power whereas the squirrel cage motor is brushless.
• The copper loss in the phase wound motor is high as compared to squirrel cage motor.
• The efficiency of the slip ring motor is low whereas the squirrel cage motor has high efficiency.
• The speed of the phase wound motor is controlled by using the resistance circuit. It is impossible to control the speed of the squirrel cage motor.
• The slip ring motor has low power factor as compared to squirrel cage motor.
• The cost of the phase wound rotor is high because it consists brushes. The squirrel cage motor is cheap.
• The starting current of the phase wound rotor is low because it is controlled by resistance circuit whereas it is high in squirrel cage motor.
• The phase wound motor is mostly used in places where high starting torque is required like a hoist, cranes, etc. The squirrel cage motor is used in a drilling machine, lathe machine, etc.,
• The overloading capacity of the slip ring motor is high as compared to squirrel cage motor and it is smoothly running under heavy loads. It is less sensitive and also has no abnormal heating during the starting.