1. Speed is different from magnetic field speed. If the speed of the rotor is the same as that of the stator, it is called a synchronous motor; if not, it is called an asynchronous motor.

2. Rotor speed is different. When the polar logarithm is constant, there is a strict relationship between the speed and frequency of the motor, and the rotor speed of the asynchronous motor is always less than that of the synchronous motor.

3. Different usage scenarios. In the use of the scenario, synchronous motors for the speed requirements of the strict occasions, the price is very expensive. And the asynchronous motor is commonly used in general occasions, the price is low.

Extension:

Both synchronous and asynchronous motors are ac powered motors, which are powered by a 50Hz AC power grid. The induction motor is the stator into the alternating current, generate a rotating magnetic field, and the rotor induced by the magnetic field.

In this way, the two magnetic fields cause the rotor to rotate with the stator's rotating magnetic field. Among them, the rotor is slower than the stator rotating magnetic field, there is a slip, not synchronous. So name it asynchronous machine.

An asynchronous motor has the same stator as an asynchronous motor, but its rotor is artificially added with direct current to create a constant magnetic field. In this way, the rotor is switched into synchronization with the stator's rotating magnetic field.

To put it simply, there is no DC excitation current added to the rotor of the asynchronous motor, while a DC excitation current is added to the rotor of the synchronous motor to make the rotor speed consistent with the magnetic field speed generated by stator and rotor cutting.