An electrical motor is a machine which transforms the electrical power into mechanical power. It is used by various power plants, industries and machineries.
The AC motors are sub-divided into two major categories which include synchronous and induction motors (also known as asynchronous motor) which are quite different from each another.
A three-phase synchronous motor is a double-excited machine, whereas the induction motor is single excited machines.
The major difference between synchronous and asynchronous motor is the speed of the rotor that is aligned with the direction of the rotating magnetic field in the stator. In case of the same rotation speed and stator field speed, it will be synchronous motor otherwise will be considered as an asynchronous motor.
The speed of the induction motor is always lower than the synchronous motor speed, and it usually relies on the load, also the speed decreases when the load increases. On the other hand, the synchronous motor can be operating at synchronous speed i-e Ns = 120f/P. It does not matter how much the loads would be because these kinds of motor do not depend on the loads.
Furthermore, there are other broad variations between the two based on the output criteria and applications.
Construction of the motor:
Major differences between induction and synchronous motor: