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COMPARISON BETWEEN INDUCTION AND SYNCHRONOUS MOTORS

The comparison between induction and synchronous motors is given below:

S. No. Induction motor Synchronous motor
1. It has got self-starting torque and no special means are required for starting. It is inherently not self-starting and some external means are required for its starting.
2. Does not require D.C. excitation. Requires D.C. excitation.
3. Speed can be controlled but to small extent. Speed control not possible.
4. Its speeds falls with the increase in load and is always less than synchronous speed. Its average speed is constant and independent of load.
5. It operates at only lagging power factor, which becomes very poor at light loads. It can be operated under a wide range of power factor, both lagging and leading.
6. Its torque is more sensitive to change in supply voltage. Its torque is less sensitive to change in supply voltage.
7. Breakdown torque is proportional to the square

of the supply voltage.

Breakdown torque is proportional to the supply voltage.
8. More simple and less costly comparatively. More complicated and more costly comparatively.
9. Employed for supplying mechanical load only. Employed for supplying mechanical load as well as for power factor improvement