Magnetic field analysis and magnetic circuit design of permanent magnet motor

Previously, the editor has introduced in detail the design and selection of permanent magnets for permanent magnet motors. It can be seen that the permanent magnet design of the motor is mainly determined by the shape of the permanent magnets and the structure of the magnetic poles, and the permanent magnets should be able to operate within the designated operating space. To generate the required magnetic field, the magnetic field established by the permanent magnet should have high stability, and the magnetic performance should be within the allowable range as the operating temperature and environment change.

With the continuous development of the motor technology industry, motors with new structures and new principles are constantly emerging in major markets, especially permanent magnet motors, which have flexible and diverse magnetic circuit structures and complex magnetic field distribution, which brings great challenges to magnetic circuit calculations. It is difficult to obtain accurate magnetic circuit calculation results.

To ensure the accuracy of design calculations, we need to perform numerical calculations and analysis of magnetic fields. So what are the magnetic field analysis and magnetic circuit design of permanent magnet motors? Let’s take a look below!

The magnetic field numerical methods of permanent magnet motors include: finite element method, finite difference method, boundary element method, etc. The widely used method at present is the finite element method, which was proposed in the 1940s. It was used in aircraft design in the 1950s and was applied to the field of electromagnetic engineering in the 1960s and 1970s. Its outstanding advantages are as follows:

① Suitable for definite solution problems with complex boundary shapes or boundary conditions and complex media;

②The analysis process is easy to standardize, a universal calculation program can be obtained, and it has high calculation accuracy;

③Able to solve nonlinear problems. Therefore, the finite element method is particularly suitable for solving magnetic field problems such as motors with complex boundary shapes and material nonlinearity.

The magnetic circuit design of a permanent magnet motor is to rationally select the parameters and materials of the magnetic circuit based on the requirements for the magnetic field, and design a magnetic circuit that is technically feasible, has characteristics that meet the requirements, is economical, and can give full play to the material properties. For a given magnetic circuit, the characteristics of its magnetic circuit can be obtained.

However, if the characteristic requirements of a magnetic circuit are given, there may be many magnetic circuits that need to meet the requirements, and the purpose of design is to find a magnetic circuit that meets the requirements. The general design process is as follows: , based on the requirements of the magnetic circuit characteristics, initially determine the approximate magnetic circuit structure, determine the size and materials of each part of the magnetic circuit, and then use appropriate magnetic circuit calculation methods to calculate the characteristics of the magnetic circuit. If the error between the calculation results and the performance requirements is within the allowable range, the magnetic circuit design is completed; if it exceeds the allowable range, the size of the magnetic circuit needs to be adjusted, and the material and magnetic circuit structure may even be changed until a reasonable magnetic circuit is obtained. road.

Therefore, the magnetic circuit design of a permanent magnet motor mainly depends on determining the overall structure of the magnetic circuit, the size of the magnetic circuit and the selection of corresponding materials.