Induction motor is an AC motor, the ratio of the load speed and the speed of their connection with the power grid is not stable. Changes also occur with the size of the load. The load torque is greater, the rotor speed is lower. Asynchronous motors including induction motor, double-fed asynchronous motor and AC motor commutator. Induction motor is most widely used, in the case of not misleading or confusing, generally referred to the induction motor as asynchronous motor.
Ordinary asynchronous motor stator windings is connected with AC power, rotor windings need not connect to other power. Therefore, it has a simple structure, easy manufacturing, use and maintenance, reliable operation and low mass, low cost and other advantages. Induction motors have higher operating efficiency and better operating characteristics, approaching to constant speed within the range from no load to full load. That can satisfy most transmission requirements of industrial and agricultural mechanical production . Induction motors are easy to derive various types of protection, in order to adapt to different environmental conditions. While asynchronous motor is running, must draw the reactive excitation power from the grid, thus grid power factor becomes worse. Therefore, for the drive ball mill, compressors and other high-power, low-speed mechanical equipment, often using synchronous motors. Because the induction motor speed and its speed rotating magnetic field have a certain slip relationship, the speed performance is poor (except AC commutator motor). For requiring broader speed and smooth transportation machinery, rolling mill, large machine tools, printing and paper machinery, DC motor is more economical and convenient. But with the development of high-power electronic devices and AC variable speed system, speed control performance and economy efficiency of induction motor for wide speed is good as DC motor.
Induction motors are mainly used as a motor, its power ranges from a few watts to kilowatts, is the most widely used electric motor in national economy and people's daily life, providing power for a variety of mechanical equipment and household appliances. Such as machine tools, small and medium sized steel rolling equipment, fans, pumps, light machinery, metallurgical and mining machinery, mostly using three-phase induction motors (asynchronous Motor) drive; in the electric fans, washing machines, refrigerators, air conditioners and other appliances, single-phase asynchronous motors are widely used. Induction motors can also be used as a generator for the wind power plants and small hydroelectric power plants.