Exploring Three Phase Asynchronous Motors: A Comprehensive Analysis of Structure, Principle, and Application

Introduction to Three phase Asynchronous Motor

Three phase asynchronous motors are widely used in various industries due to their simple structure, reliable operation, low price, strong overload capacity, and easy installation, use, and maintenance process. In industrial production, it can be used for various machines and equipment such as compressors, pumps, fans, conveyors, grinders, cutting machines, etc; In the field of transportation, it can be used for electric vehicles, electric trains, electric boats, etc; In agricultural production, it can be used for irrigation equipment, harvesters, threshing machines, mixers, etc; Three phase asynchronous motors are also used in household and commercial appliances such as air conditioners, refrigerators, washing machines, vacuum cleaners, and electric fans.

Structure of three-phase asynchronous motor

Stator: It is a stationary part composed of three parts: iron core, winding, and machine base.

Stator iron core: a part of the motor magnetic circuit, on which the stator winding is placed. It is usually made by punching and laminating silicon steel sheets with insulation layers on the surface of 0.35-0.5 millimeters thick. There are evenly distributed slots punched in the inner circle of the iron core for embedding the stator winding. The stator core slot types include semi closed slot, semi open slot, and open slot. Half closed slot motors have higher efficiency and power factor, but winding embedding and insulation are difficult, and are generally used in small low-voltage motors; The semi open slot can accommodate molded windings and is generally used for large and medium-sized low-voltage motors; The open slot is used to embed molded windings, and the insulation method is convenient. It is mainly used in high-voltage motors.

Stator winding: It is the circuit part of an electric motor that is supplied with three-phase AC power to generate a rotating magnetic field. Composed of three identical windings arranged symmetrically at an electrical angle of 120 ° in space, each coil is embedded in a certain pattern in each slot of the stator. The main insulation items of the stator winding include ground insulation, phase to phase insulation, and turn to turn insulation, which ensure reliable insulation between the conductive parts of the winding and the iron core, as well as reliable insulation between the windings themselves. On the terminal block inside the motor junction box, the six wire ends of the three-phase winding are arranged in two rows, with specified numbering. The three-phase winding can be connected in a star or delta configuration.

Machine base: Fix the stator iron core and front and rear end caps to support the rotor and provide protection, heat dissipation, and other functions. The base is usually made of cast iron. The base of large asynchronous motors is generally welded with steel plates, while the base of micro motors is made of cast aluminum. There are heat dissipation ribs on the outside of the enclosed motor base to increase the heat dissipation area, and ventilation holes are opened on both ends of the protective motor base cover to allow direct convection of air inside and outside the motor, which is conducive to heat dissipation.

2. Rotor: It is a rotating part composed of iron core and winding.

Rotor iron core: As a part of the motor magnetic circuit and placing rotor windings in the iron core slot. The material used is the same as the stator, made by punching and laminating 0.5mm thick silicon steel sheets. The outer circle of the silicon steel sheets is punched with evenly distributed holes to accommodate the rotor winding. Usually, the inner circle of silicon steel sheets after punching the stator core is used to punch the rotor core. The rotor iron core of a typical small asynchronous motor is directly pressed onto the shaft, while the rotor iron core of a large or medium-sized asynchronous motor is pressed onto the shaft with the help of a rotor bracket.