A three-phase asynchronous motor is a type of induction motor that is powered by a 380V three-phase alternating current (120 degrees phase difference). The rotor and stator rotate due to the three-phase asynchronous motor. The magnetic field rotates in the same direction and at different rotational speeds, and there is a slip rate, so it is called a three-phase asynchronous motor. The rotation speed of the rotor of the three-phase asynchronous motor is lower than the rotation speed of the rotating magnetic field, and the rotor winding generates electromotive force and current due to the relative motion between the magnetic field and the magnetic field, and interacts with the magnetic field to generate electromagnetic torque to realize energy conversion.
Compared with single-phase asynchronous motors, three-phase asynchronous motors have good running performance and can save various materials. According to the rotor structure, three-phase asynchronous motors can be divided into two types: cage type and winding type. The asynchronous motor of the cage rotor has simple structure, reliable operation, light weight and low price, and has been widely used. The main disadvantage is that the speed regulation is difficult. The rotor of the wound-type three-phase asynchronous motor is also provided with a three-phase winding like a stator and is connected to an external varistor through a slip ring and a brush. Adjusting the varistor resistance improves the starting performance of the motor and regulates the speed of the motor.