Permanent Magnet Motor

Permanent magnet synchronous motor is mainly composed of stator, rotor, end cover and other components. The stator is laminated to reduce iron loss during motor operation. It is equipped with three-phase AC winding, called armature. The rotor can be made of solid or pressed by laminations, and is equipped with permanent magnet materials. According to the different positions of the permanent magnet materials on the motor rotor, the permanent magnet synchronous motor can be divided into two structural forms: protruding type and built-in type. The corresponding schematic diagram is given in Figure 1. The magnetic circuit structure of the protruding rotor is simple, and the manufacturing cost is low. However, because the starting winding cannot be installed on its surface, asynchronous starting cannot be realized. 

The magnetic circuit structure of the built-in rotor mainly includes radial type, tangential type and hybrid type. The difference between them is mainly due to the difference between the magnetization direction of the permanent magnet and the rotation direction of the rotor. Figure 2 shows the magnetic circuit structures of three different types of built-in rotors. As the permanent magnet is placed inside the rotor, the surface of the rotor can be made into pole shoes. The pole shoes can be started and damped by inserting copper bars or cast aluminum, and have good steady and dynamic performance. Because of the asymmetry of the built-in rotor magnetic circuit, the reluctance torque will be generated during operation, which is helpful to improve the power density and overload capacity of the motor itself, and this structure is easier to achieve weak magnetic field expansion.