Difference Between Induction Motor and Synchronous Motor


Synchronous Motor :


     A device which converts as electrical energy into a mechanical energy running at synchronous speed is called as synchronous motor. Its speed is constant irrespective of load. It is doubly excited machine because its field winding is excited from a separate dc source.



Induction Motor ( asynchronous motor ) :


     It is a asynchronous motor which means these motor do not operate at synchronous speed and their speed varies with the load. There are various types of induction motors depends upon the construction. An induction motor is an singly excited machine. It does not require any dc excitation. Its stator winding is directly connected to an ac.supply, where as the rotor winding receives energy from stator by means of induction ( transformer action ).



Difference Between Induction Motor and Synchronous Motor :


S.no.

Synchronous Motor

Induction Motor

1.

It is not self-starting.

It is self-starting.

2.

Construction is complicated.

Construction is simple, particularly in case of cage motor.

3.

It runs at constant speed i.e., synchronous speed irrespective of the load.

It can not run at synchronous speed. The speed decreases as the load increases.

4.

Speed control is not possible.

Sped control is possible.

5.

It is doubly excited machine and requires dc excitation.

It is singly excited machine and does not requires any dc excitation.

6.

It can operate with wide range of power factors both lagging and leading.

It always operates at lagging power factor.

7.

It is used for supplying mechanical loads as well as for p.f. improvement.

It is used for supplying mechanical loads only.

8.

It torque is less sensitive to change in supply voltage.

It torque is more sensitive to change in supply voltage.

9.

Hunting starts as loads changes suddenly.

Phenomenon of hunting is absent.

10.

It is very costiler and requires the maintenance.

It is cheaper and almost maintenance free particularly is case of cage motors.



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