AC asynchronous motors are widely used in electric fans, refrigerators, washing machines, air conditioners, hair dryers, vacuum cleaners, range hoods, dishwashers, electric sewing machines, food processors and other household appliances, as well as various power tools and small electromechanical equipment.

AC asynchronous motors are divided into induction motors and AC commutator motors. Induction motors are further divided into single-phase asynchronous motors, AC and DC motors and repulsion motors. The speed of the motor (rotor speed) is less than the speed of the rotating magnetic field, so it is called an asynchronous motor. It is basically the same as an induction motor. s=(ns-n)/ns. s is the slip, ns is the magnetic field speed, and n is the rotor speed.

Fundamental:

1. When the three-phase asynchronous motor is connected to the three-phase AC power supply, the three-phase stator winding flows through the three-phase magnetomotive force (stator rotating magnetomotive force) generated by the three-phase symmetrical current and generates a rotating magnetic field.

2. The rotating magnetic field and the rotor conductor have a relative cutting motion. According to the principle of electromagnetic induction, the rotor conductor generates an induced electromotive force and an induced current.

3. According to the law of electromagnetic force, the current-carrying rotor conductor is subjected to electromagnetic force in the magnetic field to form electromagnetic torque, which drives the rotor to rotate. When there is a mechanical load on the motor shaft, it outputs mechanical energy.

An asynchronous motor is an alternating current motor, and the ratio of its rotational speed under load to the frequency of the connected grid is not a constant relationship. It also varies 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 widely used, and can generally be called asynchronous motors without causing misunderstanding or confusion. The stator winding of an ordinary asynchronous motor is connected to the AC power grid, and the rotor winding does not need to be connected to other power sources. Therefore, it has the advantages of simple structure, convenient manufacture, use and maintenance, reliable operation, small quality and low cost.

Asynchronous motors have high operating efficiency and good working characteristics, and can run at a constant speed from no-load to full-load, which can meet the transmission requirements of most industrial and agricultural production machinery. Asynchronous motors are also easy to derive into various protection types to meet the needs of different environmental conditions.

When the asynchronous motor is running, it absorbs reactive excitation power from the power grid, which makes the power factor of the power grid worse. Therefore, synchronous motors are often used to drive high-power, low-speed mechanical equipment such as ball mills and compressors.

Since the speed of the asynchronous motor has a certain slip relationship with the speed of its rotating magnetic field, its speed regulation performance is poor (except for the AC commutator motor). For transportation machinery, rolling mills, large machine tools, printing and dyeing and paper-making machinery, etc. 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 now comparable to those of DC motors.