The electric motor is a device that converts electrical energy into mechanical energy. In machinery, metallurgy, petroleum, coal, chemical, aviation, transportation, agriculture and various other industries, electric motors are widely used. With the increasing degree of industrial automation, it is necessary to use a variety of control motors as components of the automation system, the automatic control system of artificial satellite, the motor is also indispensable. In addition, electric motors are more and more widely used in national defense, culture and education, medical treatment and daily life (in the modern home appliance industry). Electric motors have been implemented in the export product quality licensing system, without the export quality license products are not allowed to export. General electric motors are mainly composed of two parts: the fixed part is called stator and the rotating part is called rotor. In addition, there are end caps, fans, covers, chassis, junction boxes and so on. The stator is used to generate the magnetic field and as the mechanical support of the motor. The stator of an electric motor consists of three parts: the stator core, the stator windings and the seat. The stator winding is embedded in the stator core, which generates induced electromotive force when passing current and realizes electric energy conversion. The role of the seat is mainly to fix and support the stator core. When the motor is running, the heat generated due to internal losses is transferred to the seat through the core, and then emitted to the surrounding air by the surface of the seat. In order to increase the heat dissipation area, the motor is generally designed as a heat sink on the outer surface of the chassis. The rotor of an electric motor consists of a rotor core, rotor windings and a rotor shaft. The rotor core also acts as part of the magnetic circuit of the motor. The rotor windings serve to induce electric potential, which is passed through the current and produces electromagnetic torque. The rotor shaft is the main component that supports the weight of the rotor, transmits the torque and outputs the mechanical power. The working principle of an electric motor is based on the laws of electromagnetic induction, the law of full current, the law of electric circuits and the law of electromagnetic force. Three-phase AC asynchronous motor rotor rotation schematic (the figure shows only two guide bars), when the magnetic poles rotate in the clockwise direction, the magnetic poles of the magnetic line of force cutting the rotor guide bars, the guide bars in the induction of electric potential. The direction of the electromotive force is determined by the right-hand rule. Because the movement is relative, if the magnetic pole does not move, the rotor guide strip rotates in the counterclockwise direction, the guide strip can also be induced in the electric potential. Under the action of the electric potential, the closed guide strip in the current. The current interacts with the magnetic field of the rotating pole, and the rotor guide bar is subjected to electromagnetic force F, the direction of electromagnetic force can be determined by the left hand rule. The direction of the electromagnetic force can be determined by the left hand rule. The electromagnetic torque is generated by the electromagnetic force, and the rotor rotates.