There are two types of 3 phase induction motor. These are squirrel cage induction motor & slip ring induction motor. We shall discuss the application of squirrel cage induction motor & slip ring induction motor in this article. The principle of working of squirrel cage and slip ring induction motor is based on Faraday’s law of electromagnetic induction. The torque of the induction motor depends on the rotor resistance.
The rotor of a squirrel cage induction motor is shortcircuited by the end rings and it is not possible to connect external resistance to the rotor winding. Whereas, it is possible in slip ring induction motor.
The starting torque of the squirrel cage motor is low, therefore the motor is not suitable for the applications that demand higher starting torque. The starting torque of the squirrel cage induction motor can be improved by use of double cage rotor.
Applications of Squirrel Cage Induction Motor
The squirrel cage induction motor is suitable for the application where;
 The moderate starting torque is required
 The constant speed is required.( The speed can be controlled through VFD). The induction motor is fairly a constant speed motor.
Applications of Slip ring Induction Motor
The slip ring induction motor is suitable for the application where,
 The applications which demand higher starting torque needs a slip ring induction motor. Therefore, slip ring induction motor is suitable for driving high inertia loads.
 The speed control is required ( the speed can be controlled through Grid resistance regulator. Also, there is substantial power saving if used for driving the centrifugal fans and pumps. The other option of power saving is the slip power recovery system. The rotor copper loss or the slip power is recovered and back feed to the mains. Thus, with the use of SPRS, the total recovery of the slip power is possible. The SPRS is more efficient than GRR.

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