Slip Ring vs Squirrel Cage Induction Motor: Difference and Comparison

A slip-ring induction motor has a wound rotor with a set of slip rings and brushes that allow external resistors to be added to the rotor circuit. A squirrel cage induction motor, also known as a cage induction motor, has a rotor with a series of conductive bars connected by end rings.

Key Takeaways

  1. Slip ring induction motors have wound rotors with external brushes and slip rings, while squirrel cage induction motors have shorted bars embedded in the rotor.
  2. Slip-ring induction motors allow for better starting torque and adjustable speed control than squirrel cage induction motors.
  3. Squirrel cage induction motors are more robust, reliable, and require less maintenance than slip-ring induction motors due to their simpler construction.
Slip Ring vs Squirrel Cage Induction Motor
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What is Slip Ring Induction Motor?

These induction motors are those that use a rotor with a slip ring. Three of the ends are exposed and linked to other slip rings, and their construction is based on three-phase windings wound in a star configuration. 

It features a cylindrical core made of laminated steel, and its perimeter includes a groove that is only partially open so that a three-phase insulated winding circuit may be installed. When the motor is on, a short circuit forms automatically between these three terminals. Since the stator has a fixed number of poles, the rotor must also have a fixed number of poles.

Its top speed is reached when there is no load on it and decreases as the load increases. The rotational speed can be adjusted by up to 5%. 

A greater number of windings, higher induced voltage, and lower current may be found in the rotor in comparison to a squirrel-cage rotor. Slip rings link a motor’s windings to an external resistance, allowing for finer regulation of the motor’s torque and speed.

These motors are put to use in situations calling for both strong torque and low beginning current. It has a wide variety of possible uses, for example, in lifts, compressors, cranes, conveyors, hoists, and many others. 

However, there are certain drawbacks to this. It’s more expensive, for instance. In addition, there is additional upkeep required since the rotor must be wired into the external circuit.

What is Squirrel Cage Induction Motor?

These induction motors use electromagnetic energy to create motion. The rotor, the internal part attached to the output shaft, is shaped like a cage, thus the “squirrel cage” motor. 

The conducting metal (aluminum or copper) is implanted into the steel laminations that make up the cylinder that serves as the rotor. A spinning magnetic field is created after an AC is sent with the help of stator windings. Consequently, a current is sparked in the rotor winding, creating an independent magnetic field. 

One of the best features of a squirrel cage motor is how simple it is to modify the speed-torque characteristics. Simply altering the rotor’s bar form will do this. Because of their dependability, self-starting ability, and versatility, squirrel cage induction motors find widespread usage in manufacturing.

There are a wide variety of industrial uses for squirrel cage induction motors. They shine in situations where a steady speed, self-starting motor, or low maintenance requirements are prioritized. Machine tools, lathes, and other turning equipment, as well as centrifugal pumps, industrial drives, huge blowers, and fans, etc., all rely on these motors.

Difference Between Slip Ring and Squirrel Cage Induction Motor

  1. Slip Ring Induction Motors have a higher starting torque in comparison
  2. Slip Ring Induction Motors are higher in maintenance in comparison to Squirrel Cage Induction motors.
  3. The heat regulation is better in Squirrel Cage Induction Motor than in Slip Ring Induction Motor.
  4. Among both of them, Slip Ring Induction Motors tend to have lower pull-out torque.
  5. When it comes to induction motors, Slip Ring is less efficient than Squirrel Cage.
  6. Slip Ring Induction Motors are more convenient when it comes to speed control than Squirrel Cage Induction Motors.

Comparison Between Slip Ring and Squirrel Cage Induction Motor

Parameters of ComparisonSlip Ring Induction MotorSquirrel Cage Induction Motor
Starting TorqueHighLow
MaintenanceHighLow
Heat RegulationPoorGood
Pull-out TorqueLesserGreater
EfficiencyLess efficientMore efficient.
Speed ControlEasierMore difficult.
Difference Between Slip Ring and Squirrel Cage Induction Motor
References
  1. https://iopscience.iop.org/article/10.1088/1742-6596/1402/3/033107/meta
  2. https://digital-library.theiet.org/content/journals/10.1049/jiee-1.1928.0034

Last Updated : 29 July, 2023

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