Motor is a device that converts electrical energy into mechanical energy. It uses the energized coil (i.e. the stator winding) to generate the rotating magnetic field and act on the rotor (such as the squirrel-cage closed aluminum frame) to form the magneto-electrodynamic rotating torque. Motors are divided into DC motors and AC motors according to the different power sources used. Most of the motors in the power system are AC motors, which can be synchronous motors or asynchronous motors (the speed of the stator magnetic field of the motor is not synchronous with the speed of the rotor rotation). The motor is mainly composed of stator and rotor. The direction of force movement of energized wire in the magnetic field is related to the direction of current and magnetic induction line (magnetic field direction). The working principle of the motor is that the magnetic field acts on the force of the current to make the motor rotate.