Difference Between Induction and Synchronous Motor is explained with the help of various factors, like the type of excitation used for the machine. The speed of the motor, starting and operation, the efficiency of both the motors, its cost, usage, applications, and frequency.
| BASIS OF DIFFERENCE | SYNCHRONOUS MOTOR | INDUCTION MOTOR |
|---|---|---|
| Type of Excitation | A synchronous motor is a doubly excited machine. | An induction motor is a single excited machine. |
| Supply System | Its armature winding is energized from an AC source and its field winding from a DC source. | Its stator winding is energized from an AC source. |
| Speed | It always runs at synchronous speed. The speed is independent of load. | If the load increased the speed of the induction motor decreases. It is always less than the synchronous speed. |
| Starting | It is not self starting. It has to be run up to synchronous speed by any means before it can be synchronized to AC supply. | Induction motor has self starting torque. |
| Operation | A synchronous motor can be operated with lagging and leading power by changing its excitation. | An induction motor operates only at a lagging power factor. At high loads the power factor becomes very poor. |
| Usage | It can be used for power factor correction in addition to supplying torque to drive mechanical loads. | An induction motor is used for driving mechanical loads only. |
| Efficiency | It is more efficient than an induction motor of the same output and voltage rating. | Its efficiency is lesser than that of the synchronous motor of the same output and the voltage rating. |
| Cost | A synchronous motor is costlier than an induction motor of the same output and voltage rating | An induction motor is cheaper than the synchronous motor of the same output and voltage rating. |
An Induction Motor is also known as Asynchronous Motor. It is so called because it never runs at synchronous speed. i.e., Ns = 120f/P. The induction motor is most widely used motor in all domestic and commercial motor. The synchronous motor always follows a synchronous speed. The speed of the rotor is maintained or synchronized with the supply current.
Difference between Three Phase Induction Motor and Synchronous Motor
- A three-phase synchronous motor is a doubly excited machine, whereas an induction motor is a single excited machine.
- The armature winding of the synchronous motor is energized from an AC source and its field winding from a DC source. The stator winding of Induction Motor is energized from an AC source.
- Synchronous Motor always runs at synchronous speed, and the speed of the motor is independent of load, but an induction motor always runs less than the synchronous speed. If the load increased the speed of the induction motor decreases.
- The induction motor has self-starting torque whereas the synchronous motor is not self starting. It has to be run up to synchronous speed by any means before it can be synchronized to AC supply.
- A synchronous motor can be operated with lagging and leading power by changing its excitation. An induction motor operates only at a lagging power factor. At high loads, the power factor of the induction motor becomes very poor.
- The Synchronous Motor can be used for power factor correction in addition to the supplying torque to drive mechanical loads whereas an induction motor is used for driving mechanical loads only.
- The synchronous motor is more efficient than an induction motor of the same output and voltage rating.
- A synchronous motor is costlier than an induction motor of the same output and voltage rating.
Hence, the induction motor is different from synchronous motor.
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