An electric motor is a device that converts electrical energy into mechanical energy. It uses energized coils (i.e. stator windings) to generate a rotating magnetic field and applies it to the rotor (such as a squirrel cage closed aluminum frame) to form a magnetic electric rotational torque. Electric motors are divided into DC motors and AC motors according to the different power sources used. Most electric motors in the power system are AC motors, which can be synchronous motors or asynchronous motors (the stator magnetic field speed and rotor rotation speed of the motor do not maintain synchronous speed). The electric motor is mainly composed of a stator and a rotor, and the direction of force movement of the energized wire in the magnetic field is related to the direction of the current and the direction of the magnetic field lines (magnetic field direction). The working principle of an electric motor is that the magnetic field exerts force on the current, causing the motor to rotate.

There are many speed control methods for electric motors, which can adapt to the requirements of different production machinery speed changes. The output power of a general electric motor varies with the speed during speed regulation. From the perspective of energy consumption, speed regulation can be roughly divided into two types:

① Keep the input power constant. By changing the energy consumption of the speed regulating device, the output power is adjusted to regulate the speed of the electric motor.

② Control the input power of the electric motor to regulate its speed. Motors, electric motors, brake motors, variable frequency motors, speed regulating motors, three-phase asynchronous motors, high-voltage motors, multi speed motors, dual speed motors, and explosion-proof motors.