1, when three-phase asynchronous motor is connected to three-phase AC power supply, three-phase stator winding flows through three-phase symmetrical current generated three-phase magnetomotive force (stator rotating magnetomotive force) and produces rotating magnetic field.
2. The rotating magnetic field has relative cutting motion with the rotor conductor. According to the principle of electromagnetic induction, the rotor conductor generates inductive electromotive force and produces inductive current.
3, according to the law of electromagnetic force, the rotor of the current carrying rotor is affected by electromagnetic force in the magnetic field, forming electromagnetic torque, driving the rotor to rotate, when the motor shaft with mechanical load, then output mechanical energy.
Asynchronous motor is a kind of AC motor, its load speed and the frequency of the power grid is not constant relationship. It changes with the size of the load. The greater the load torque is, the lower the rotor speed is. Asynchronous motor includes induction motor, double fed induction motor and AC commutator motor. The most widely used induction motor, in the case of not causing misunderstanding or confusion, generally referred to as induction motor for induction motor.
The stator winding of common asynchronous motor is connected to AC power grid, and the rotor winding does not need to connect with other power supply. Therefore, it has the advantages of simple structure, convenient manufacture, use and maintenance, reliable operation, small quality and low cost. Asynchronous motor has higher running efficiency and better working characteristics. It can run at constant speed from no-load to full load range, which can meet the transmission requirements of most industrial and agricultural production machinery. Asynchronous motor is also easy to generate various protection types to meet the needs of different environmental conditions. When the asynchronous motor is running, the reactive excitation power must be drawn from the grid so that the power factor of the power grid will deteriorate. Therefore, the synchronous motor is often used to drive the ball mill, compressor and other mechanical equipment with high power and low speed. Because the speed of asynchronous motor has a certain turning relation with the rotating speed of rotating magnetic field, its speed control performance is poor (except for AC commutator motor). It is economical and convenient to use DC motor to transport machinery, rolling mills, large machine tools, printing and dyeing machines and paper machines, which require wider and smooth speed range. But with the development of high power electronic devices and AC speed regulation system, the speed regulating performance and economic efficiency of asynchronous motor with wide speed regulation can be comparable to that of DC motor.