What is a three-phase asynchronous motor? What is the principle?

A three-phase asynchronous motor is a type of motor that relies on the simultaneous connection of a 380V three-phase AC power supply. Due to the fact that the rotating magnetic field of the rotor and stator of the three-phase asynchronous motor rotates in the same direction but at different speeds, there is a slip rate, so it is called a three-phase asynchronous motor. The rotor speed of the three-phase asynchronous motor is lower than the speed of the rotating magnetic field, and the rotor winding generates electromotive force and current due to the relative motion with the magnetic field, and interacts with the magnetic field to generate electromagnetic torque, achieving energy transformation.

A three-phase motor is a machine that uses electricity to drive the brush to rotate, and then serves as a power source. Three phases refer to the use of three-phase electricity, which means that every two of the three wires are 380V. Asynchronous means that the rotating magnetic field of the stator is always one angle higher than the rotor, so that the motor can rotate in the required direction.

Compared with single-phase asynchronous motors, three-phase asynchronous motors have better operating performance and can save various materials. According to the different rotor structures, three-phase asynchronous motors can be divided into cage type and wound type. The cage type rotor asynchronous motor has a simple structure, reliable operation, affordable price, small size, and light weight, and has been widely used. Its main disadvantage is difficult speed regulation. The rotor and stator of wound three-phase asynchronous motors are also equipped with three-phase windings and connected to external variable resistors through slip rings and brushes. Adjusting the resistance of the variable resistor can improve the starting performance of the motor and adjust the motor speed.

The difference between three-phase synchronous motors and three-phase asynchronous motors is that asynchronous motors belong to AC motors, and the stator winding is the same as asynchronous motors. Its rotor rotation speed is the same as the speed of the rotating magnetic field generated by the stator winding, so it is called synchronous motors. Because of this, the current of synchronous closed circuit motors is ahead of voltage in phase, that is, synchronous motors are capacitive loads. Therefore, in many cases, synchronous motors are used to improve the power factor of the power supply system.

However, the frame of a three-phase asynchronous motor, also known as the casing, is mainly used to support the stator core and also withstand the reaction force generated during the operation of the entire motor load. During operation, the heat generated due to internal losses is also dissipated outward through the frame. The frame of small and medium-sized electric motors is generally made of cast iron. For large electric motors, due to the large size of the body and inconvenient pouring, steel plates are commonly welded and formed. The structure consists of two basic parts: a fixed stator and a rotating rotor. The rotor is installed in the stator cavity and supported by bearings on two end caps. In order to ensure that the rotor can rotate freely in the stator, there must be a gap between the stator and rotor, called an air gap. The air gap of the motor is a very important parameter, and its size Symmetry and other factors have a significant impact on the performance of electric motors.