Squirrel Cage Induction Motor vs Slip Ring Induction Motor

Squirrel Cage Induction Motor vs Slip Ring Induction Motor

Comparison of Squirrel cage induction motor with slip ring induction motor (Wound Rotor Induction Motor) is listed in the below table:

Squirrel Cage Induction Motor Slip ring (wound rotor) Induction Motor
In Squirrel cage induction motors the rotor is simplest and most rugged in construction In slip ring induction motors the rotor is wound type. In the motor the slip rings, brushes are provided. Compared to squirrel cage rotor the rotor construction is not simple.
Cylindrical laminated core rotor with heavy bars or copper or aluminium or alloys are used for conductors. Cylindrical laminated core rotor is wound for as the number of poles of the stator.
Rotor conductors or rotor bars are short circuited with end rings. At starting the 3 phase windings are connected to a star connected rheostat and during running
condition, the windings is short circuited at the slip rings.
Rotor bars are permanently short circuited and hence it is not possible to connect external resistance in the circuit in series with the rotor conductors. It is possible to insert additional resistance in the rotor circuit. Therefore it is possible to increase the torque ( the additional series resistance is used for starting purposes)
Cheaper cost Cost is slightly higher.
No moving contacts in the rotor. Carbon brushes, slip rings etc are provided in the rotor circuit.
Higher efficiency. comparatively less efficiency.
Low starting torque. It is 1.5 time full load torque. High starting torque. It can be obtained by adding external resistance in the rotor circuit.
Speed control by rotor resistance is not possible. Speed control by rotor resistance is possible.
Starting current is 5 to 7 times the full load. Less starting current.

Advantages of Squirrel-Cage Induction Motors

The advantages of squirrel-cage motors compared with the slip ring induction motors are given below

(i) They are more robust and cheaper
(ii) Comparatively they have  higher efficiency and power factor
(iii) Since the risk of sparking is eliminated by the absence of slip rings and brushes, they are explosion-proof.

Advantages of Slip ring Induction Motors

The advantages of the wound rotor (Slip ring) Induction motors compared with the squirrel-cage motors are given below

(i) They have very high starting torque
(ii) They have very low starting current
(iii) They have a means of varying speed by use of external rotor resistance.

Read More:
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14 Responses

  1. Ankita says:

    This article gives brief differences between squirrel cage induction moto and wound rotor.
    A good article if one is looking for brief differences between the two motors.

  2. Ronish Lal says:

    thanks alot! made my work easier

  3. T.SANTOSH says:

    Super article

  4. Amir Kazemi says:

    what is the ratio of weight difference between Slip Ring induction motor and Squirell cage induction motor with the same performance and frame size?

  5. Amir Kazemi says:

    What is the weight difference ratio (percentage) between squirrel cage induction motor and slip ring induction motor with same performance and frame size

  6. rahul sinha says:

    Great artical

  7. Ratikanta says:

    Super method

  8. S .Singh says:

    thank you for about slip ring and squirrel cage induction

  9. Muhammad Ghazi Abbas says:

    Can any one explain , , in 3 phase induction motor the relation of torque with Rotor resistance , , ?
    according to me torque does not depend on rotor resistance, ,

  10. Siddhant snehi says:

    Briefly described in good manner

  11. Hassan says:

    Good with diagram

  12. prasant says:

    This give brief knowledge about these 2motor

  13. Rushikesh says:

    Thanks a lot for this brief information 👍

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