22 Difference between Squirrel Cage and Slip Ring (Wound) Induction Motor

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The rotor is a basic fundamental part of an electric motor that generates a rotating field. For the generation of an electromagnetic field, the rotor is constructed in the form of a squirrel cage type of rotor or slip ring type of rotor.

Depending upon the type of rotor which is used in the three-phase induction motor, a three-phase induction motor is classified into two types.

  1. Squirrel Cage Induction Motor
  2. Slip Ring (Wound) Induction Motor

These two induction motors are used in different functionalities based on their salient features.

Let’s see what is the difference between squirrel cage and slip ring induction motor considering basic specifications.

Squirrel Cage vs Slip Ring (Wound) Induction Motor in Tabular Form

#ContentSquirrel-Cage MotorSlip Ring (Wound) Motor
01Construction of squirrel-cage & slip ring motorThe construction of the squirrel-cage rotor is very simple as compared to the slip ring rotor of the motor. The construction of the squirrel-cage rotor is difficult due to the connected slip rings and bushes.
02Called asSometimes, a squirrel cage motor is called as Cage motor. Slip ring motor is called as Wound motor.
03Internal Connection of Rotor & StatorIn an internal connection of the squirrel-cage motor, rotor winding is similar to the stator winding. In an internal connection of the slip ring motor, the rotor consists of rotor bars that are permanently joined and shorted with the help of the end ring.
04Winding TurnsThe rotor of the squirrel-cage motor has fewer winding turns than the wound rotor.The rotor of the slip ring motor has more winding turns than the cage rotor.
05Slip rings & Brushes of squirrel cage and slipring motor. In the squirrel cage induction motor, brushes and slip rings do not require.In slip ring induction motor, brushes and slip rings are required or present.
06MaintenanceIt requires low maintenance. It requires more maintenance due to the additional brushes.
07External Resistance We do not need to add the external resistance as the rotor bars are permanently shorted in this motor. We can easily add external rotor resistance with the help of the brushes and the slip rings.
08Speed of Cage & Wound Motor The speed of the cage rotor is changed by changing the number of stator poles. The speed of the wound rotor is changed by changing the motor slip.
09Speed ControlSpeed can not be controlled or adjusted by the rotor resistance method.Speed can be easily controlled or adjusted by the rotor resistance method.
10Starting TorqueStarting torque of squirrel cage induction motor is minimum. Starting torque of the slip ring induction motor is maximum.
11Starting CurrentIt provides a high starting current.It provides a low starting current.
12CostIt is cheaper than the wound motor.It is very costlier than the cage motor.
13Efficiency of both motorThis motor provides more efficiency. This motor provides less efficiency.
14Copper Losses in of squirrel cage motor & wound motorFewer copper losses occur in squirrel cage motor.The copper loss in the slip ring motor is more.
15Power FactorIt cannot improve the power factor.It can improve the power factor.
16StarterIn 3 phase squirrel cage induction motor, the rotor resistance starter is not used. In 3 phase slip ring induction motor, the rotor resistance starter is used.
17Torque OperationWhen low starting torque is required, the squirrel cage motor is used.When high starting torque is required, the slip ring motor is used.
18Cooling SystemBetter cooling is available in this type of motor due to the presence of more space in rotor slots.Poor cooling is available in this type of motor.
19Industrial Uses In industries, squirrel cage motor is widely (approximately 90%) used. In industries, the slip ring or wound motor is rarely used.
20ExampleIn an elevator, crane, hoist, squirrel cage induction motor is used.In fan, blower, printing machine, drilling machine, conveyor, lathe, slip ring induction motor is used.
21Speed DriveThe squirrel cage motor does not require a continuously adjustable-speed drive.
The slip ring motor requires a continuously adjustable-speed drive.

22. Method of Starting of Squirrel cage motor & Wound motor

Basically the following four methods are widely used for starting the cage motor.

  • Autotransformer starting method
  • Star delta starting method
  • Direct-on-line starting method
  • Stator resistance starting method

The following four methods are available for starting the slip ring or wound motor.

  • Stator resistance starting method
  • Rotor resistance starting method
  • Autotransformer starting method
  • Direct-on-line starting method

We will talk about these methods in the upcoming article in detail.

This is all about the difference between squirrel cage and slip ring induction motor. Also, this comparison describes the advantages and disadvantages of squirrel cage induction motor and slip ring induction motor.

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