An asynchronous motor is an AC motor, and the ratio of its speed under load to the frequency of the connected power grid is not constant. It also changes with the size of the load. The greater the load torque, the lower the rotor speed. Asynchronous motors include induction motors, doubly-fed asynchronous motors and AC commutator motors. Induction motors are the most widely used, and can generally be called asynchronous motors without causing misunderstanding or confusion. Asynchronous motors are also easy to generate various protection types to adapt to the needs of different environmental conditions. When an asynchronous motor is running, reactive excitation power must be absorbed from the power grid, which deteriorates the power factor of the power grid. Therefore, synchronous motors are often used to drive high-power, low-speed mechanical equipment such as ball mills and compressors. Because the speed of an asynchronous motor has a certain slip relationship with the speed of its rotating magnetic field, its speed regulation performance is poor (except for AC commutator motors). For transportation machinery, rolling mills, large machine tools, printing and dyeing and papermaking machinery that require a wide and smooth speed regulation range, it is more economical and convenient to use DC motors. However, with the development of high-power electronic devices and AC speed regulation systems, the speed regulation performance and economy of asynchronous motors suitable for wide speed regulation are currently comparable to those of DC motors. The stator consists of a base and an iron core with windings. The iron core is formed by laminating silicon steel sheets with punched grooves. Two sets of main windings (also called running windings) and auxiliary windings (also called starting windings to form auxiliary windings) are embedded in the grooves. The main winding is connected to the AC power supply, and the auxiliary winding is connected in series with the centrifugal switch S or the starting capacitor, running capacitor, etc., and then connected to the power supply. Single-phase asynchronous motors are divided into single-phase resistance-starting asynchronous motors, single-phase capacitor-starting asynchronous motors, single-phase capacitor-running asynchronous motors and single-phase dual-value capacitor asynchronous motors. The harmonic drive of the harmonic reducer uses the controllable elastic deformation of flexible elements to transmit motion and power. It is not large in size and has high precision. However, the shortcomings are that the flexible wheel has limited life, is not resistant to impact, and its rigidity is poor compared with metal parts. The input speed cannot be too high.