According to the construction of the rotor or type of rotor, induction motor classified into two types;

• Squirrel Cage Induction Motor
• Phase Wound Induction Motor

Squirrel cage induction motor is most popular in industries and most used motor among all AC motors.  Slip ring or phase wound motor is not used more and has very fewer applications in industries.

Squirrel cage induction motor has advantages like cheaper in cost, robust construction, efficient and reliable motor. Other hands, slip ring induction motor has disadvantages like frequent maintenance and having a high copper loss.

The major difference is the external resistance circuit for controlling the speed of the motor. In the case of squirrel cage induction motor, rotor bars are short-circuited with end rings. Therefore, the external resistance cannot connect with the rotor. But in the case of the phase wound induction motor, the rotor winding has the arrangement to connect the external resistance which used to increase the starting torque and speed regulation.

In this article, we will explain the Difference Between Squirrel Cage and Phase Wound Induction Motor with different factors. Before reading this article, read the construction and classification of a three-phase induction motor.

Three Phase Induction Motor: Construction and Classification

Difference Between Squirrel Cage and Phase Wound Induction Motor

Sr.no.	Factors	Squirrel Cage Induction Motor	Phase Wound Induction Motor
1	Starting	The motor can start with a star-delta starter and it will eliminate the hazards of slip rings, brushes, gears.	The motor requires slip rings, brushes, gears, short-circuiting devices, and starting resistance.
2	Overheating	Less	More
3	Space factor in slots	Better	Poor
4	Cooling	The losses can be dissipated efficiently because the slip rings are bars and there is more space for providing an efficient fan.	Most of the space is taken by the overhang and less space is left for the provision of a good cooling fan, therefore, the cooling is not quite efficient.
5	Efficiency	High efficiency (the only machine which is not designed for high starting torque)	Low efficiency
6	Starting Torque	For plain squirrel-cage motor, starting torque is poor. But it can be increased in an ordinary way.	Starting torque can increase by the insertion of external resistance in each phase of the rotor.
7	Copper Losses	Since overhang is less and the space factor is better the copper losses are small.	Due to large overhang and poor space factor, the copper losses are more.
8	Cost	Cheaper (because of the fewer components and less labor required for winding)	The cost is more compared to the squirrel cage induction motor.
9	Construction	Simple	Complicated
10	Resistance	The rotor bars are permanently short-circuited. Therefore, the external resistance is not connected with the rotor.	The rotor winding has terminals to connect the extra resistance to increase the starting torque and speed regulation.
11	Starting Torque	Low	High
12	Brushes	Absent	Present
13	Maintenance	Less maintenance required	Frequent maintenance required
14	Starting Current	High	Low
15	Speed Control	Not possible	Possible
16	Application	Used in lathe machine, fan, blower, etc.	Used in the hoist, cranes, elevators, and the applications where high starting torque is required.

For more details of Induction Motor;

Induction Motor

 

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