Principle of three-phase motor

The working principle of a small 3 phase induction motor is based on the concept of a three-phase alternating current and rotating magnetic field. Three-phase alternating current is an alternating current composed of three sine waves with a phase difference of 120 degrees. In practical applications, a three-phase four-wire power supply method is usually adopted, that is, three-phase lines (A, B, C) and a neutral line (N). The generation and transmission of three-phase alternating current requires special power equipment, such as generators, transformers, and distribution cabinets.

In a three-phase motor, a rotating magnetic field is generated by a three-phase alternating current. When the current and voltage of the three-phase alternating current change over time, a synthetic magnetic field is generated in the stator winding of the motor. Since the phase difference of the three-phase alternating current is 120 degrees, the synthetic magnetic field will also rotate over time. This rotating magnetic field will drive the motor rotor to rotate together. Specifically, when there is a certain angle between the axis of the rotating magnetic field and the axis of the rotor magnetic field, the rotor magnetic field will be affected by the magnetic force and generate torque. This torque will cause the motor rotor to rotate in the direction of the rotating magnetic field. When the axis of the rotating magnetic field coincides with the axis of the rotor magnetic field, the torque reaches the value, and the speed of the motor also reaches the value at this time. As the rotating magnetic field continues to rotate, the torque gradually decreases and the speed of the motor also gradually decreases. When the rotating magnetic field coincides with the axis of the rotor magnetic field again, the torque reaches the value again, and this cycle repeats to achieve continuous operation of the motor.

The three-phase motor is mainly composed of two parts: the stator and the rotor. The stator is the stationary part of the motor, mainly including the stator core, stator winding, and frame. The stator core is usually made of laminated silicon steel sheets to reduce magnetic resistance and increase magnetic permeability. The stator winding is the coil of the motor, usually wound with high-strength enameled wire. The rotor is the rotating part of the motor, mainly including the rotor core, rotor winding, and shaft. The rotor core is also usually laminated with silicon steel sheets to reduce magnetic resistance and increase magnetic permeability. The rotor winding is another coil of the motor, usually wound with high-strength enameled wire. The two ends of the rotor winding are connected to the external power supply through slip rings to achieve power supply during rotation.

The induction single phase motor is a type of induction motor, powered by 380V three-phase AC (phase difference of 120 degrees) at the same time. The speed of its rotor is lower than the speed of the rotating magnetic field. The rotor winding generates electromotive force and current due to the relative motion between the rotor winding and the magnetic field and interacts with the magnetic field to generate electromagnetic torque to achieve energy conversion. Compared with single-phase asynchronous motors, three-phase asynchronous motors have better operating performance and can save various materials.