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.
- Squirrel Cage Induction Motor
- 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
| # | Content | Squirrel-Cage Motor | Slip Ring (Wound) Motor |
| 01 | Construction of squirrel-cage & slip ring motor | The 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. |
| 02 | Called as | Sometimes, a squirrel cage motor is called as ‘Cage motor‘. | Slip ring motor is called as ‘Wound motor‘. |
| 03 | Internal Connection of Rotor & Stator | In an internal connection of the squirrel-cage motor, the 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. |
| 04 | Winding Turns | The 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. |
| 05 | Slip 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. |
| 06 | Maintenance | It requires low maintenance. | It requires more maintenance due to the additional brushes. |
| 07 | External 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. |
| 08 | Speed 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. |
| 09 | Speed Control | Speed can not be controlled or adjusted by the rotor resistance method. | Speed can be easily controlled or adjusted by the rotor resistance method. |
| 10 | Starting Torque | Starting torque of the squirrel cage induction motor is minimum. | Starting torque of the slip ring induction motor is maximum. |
| 11 | Starting Current | It provides a high starting current. | It provides a low starting current. |
| 12 | Cost | It is cheaper than the wound motor. | It is very costlier than the cage motor. |
| 13 | Efficiency of both motor | This motor provides more efficiency. | This motor provides less efficiency. |
| 14 | Copper Losses in of squirrel cage motor & wound motor | Fewer copper losses occur in squirrel cage motor. | The copper loss in the slip ring motor is more. |
| 15 | Power Factor | It cannot improve the power factor. | It can improve the power factor. |
| 16 | Starter | In 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. |
| 17 | Torque Operation | When low starting torque is required, the squirrel cage motor is used. | When high starting torque is required, the slip ring motor is used. |
| 18 | Cooling System | Better 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. |
| 19 | Industrial Uses | In industries, squirrel cage motor is widely (approximately 90%) used. | In industries, the slip ring or wound motor is rarely used. |
| 20 | Example | In fan, blower, printing machine, drilling machine, conveyor, pump, lathe, squirrel cage induction motor is used. | In an elevator, crane, hoist, slip ring induction motor is used. |
| 21 | Speed Drive | The 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.
Other related Differences:
- Electric Motor vs Generator
- Synchronous Motor vs Induction Motor
- Alternating Current vs Direct Current
- Single Phase System vs Three-Phase System
- Core Transformer vs Shell Transformer
Thanks for Reading!
I have completed master in Electrical Power System. I work and write technical tutorials on the PLC, MATLAB programming, and Electrical on DipsLab.com portal.
Sharing my knowledge on this blog makes me happy. And sometimes I delve in Python programming.
Good explaination with all basic concepts.
Thank you, Raksha!
Thanks for sharing, Dipali.
Glad 🙂
Good job, Dear!
Thanks, Jimmy.
Please upload notes for Electronics and Communication.
Thanks for suggesting. Soon, I will try to cover this topic.
The slip ring motor has brushes for transferring the power whereas the squirrel cage motor is brushless.
Thanks, Animesh for adding this point.
pointwise explanation is very good, easily understandable. I will be thankful if you post comparison between LT motor v/s HT motor.
One little correction is there as per best of my knowledge, i.e. applications of squirrel cage and slip ring motor mentioned in this article is incorrect. please correct for future reference.
Slip ring induction motors are mainly used in applications where high starting torque is required such as cranes, hoists, conveyors, etc. while the squirrel cage induction motors are used in general application like lath machine, drill machine, pumps and fans, etc.
Thank you Surendra for identifying the mistake. I have edited the article.