What is the difference between asynchronous and synchronous motors?

The essential difference between a synchronous motor and an asynchronous motor is whether or not the rotational speed is synchronized (that is, the magnetic field rotational speed). Similarly, the difference is relative to the magnetic field rotational speed.

The principle of the asynchronous motor is to cut the rotating magnetic field wire to produce a stress drag motor, so if there is no magnetic field speed difference, there will be no torque to cut the magnetic field. So called asynchronous.

The principle of the synchronous motor is to drag the rotor magnetic field in the air gap of the rotating magnetic field. It can be imagined that the magnetic field of the stator is always "attracting" the rotor. If the synchronous speed is not reached, the motor will always accelerate and know the synchronization. So called synchronous motors. Synchronous motors have a relatively large power factor and are often used as generators.