Comparison between Synchronous and Asynchronous (Induction) Motor :
| Synchronous Motor | Asynchronous Motor |
| A synchronous motor is a electrical machine it convert electrical power to mechanical power & when an alternator may operate as a motor by connecting its armature winding to a 3-phase supply then it is called a synchronous motor. | Asynchronous motor is a machine whose rotor rotates at the speed less than the synchronous speed N < NS |
| Brushless motor, Variable Reluctance Motor, Switched Reluctance Motor and Hysteresis motor are the synchronous motor. | AC Induction Motor is known as the Asynchronous Motor. |
| The synchronous motor can be operated over a wide range of power factors both lagging and leading but induction motor always run with a lagging power factor which may become very low at light load | Asynchronous motor is inherently not self starting |
| Does not have slip. The value of slip is zero. | This types of motor’s value of slip is not equal to zero. |
| It requires DC excitation power source to initially rotate the rotor near to the synchronous speed. | It does not require any additional starting source. |
| Slip ring and brushes are required | Slip ring and brushes are not required. |
| Synchronous motor are usually more costly | Less costly |
| Efficiency is greater than Asynchronous motor. | It’s have Less efficient |
| By changing excitation the power factor can be adjusted accordingly as lagging, leading or unity. | Asynchronous motor runs only at a lagging power factor. |
| Current is given to the rotor of the synchronous motor | The rotor of Asynchronous motor does not require any current. |
| The Speed of the motor does not depend on the variation in the load. It is constant. | The Speed of the Asynchronous motor decreases with the increasing load. |
| Synchronous motor is not self starting | It is self starting |
| operate smoothly at low speed that is below 300 RPM | Above 600 rpm speed motor operation is excellent. |
for a given frequency the synchronous motor runs at the constant average speed whatever the load while the speed of an induction motor false somewhat with increase in load.