By function
AC motors are usually divided into several categories according to their functions: alternator, AC motor and synchronous condenser. Due to the reversibility of the motor's working state, the same motor can be used as both a generator and a motor.
It is not very accurate to divide motors into generators and motors. It is just that some motors mainly operate as generators, and some motors mainly operate as motors.
By variety
AC motors are divided into two categories: synchronous motors and asynchronous motors. The speed ns of the synchronous motor rotor is the same as the speed of the rotating magnetic field, which is called synchronous speed. There is a strict relationship between ns, the frequency of the connected alternating current (f) and the number of magnetic pole pairs (P) of the motor.