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In low temperature to high temperature of wide temperature range, vacuum, permanent magnet motor electromagnetic parameters change very big, material nonlinear change, electromagnetic field, temperature field, fluid field, stress field, such as coupling relationship between the physical field more complex, in the normal environment can ignore more physical field coupling relationship cannot be ignored, become a key technical problem.
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The motor core loss, wind friction loss and motor temperature rise are not only closely related to the environmental temperature and pressure, but also influence each other. In the vacuum environment, the heat dissipation condition is special, which is related to the shape and surface properties of the adjacent parts, and the thermal radiation is nonlinear with the surface temperature. The change of vacuum to high pressure affects the change of stress and material characteristics, which makes it more difficult to model the multiple physical field of the motor. Therefore, the coupling relationship of various physical fields in the permanent magnet motor is very complex, and it is very difficult to study the coupling relationship of each physical quantity and physical field and its dynamic change law.The multi-physical field analysis method of permanent magnet motors are numerical analytical method and finite element analysis. In terms of numerical analysis, the general modeling methods include traditional matrix method, bonding graph method, bonding method, network method and so on. Academician Zhong Jiao et al. put forward the basic theory of global coupling analysis and coupling parallel design of complex electromechanical system.
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Professor He Shanghong et al. proposed to establish a modeling matrix method for the topological structure of complex networks, and to establish a unified model of machine, electric and liquid transmission matrix. The literature uses the generalized control system to establish a unified mathematical model for the numerical simulation of engine multi-field coupling to solve the variable domain difference problem of gas, heat and elastic coupling. The node mapping method for multi-field coupling is introduced and the in-field load transfer is discussed. However, there are still many problems in coupling modeling and solution. Due to too many assumptions and ignoring factors, the calculation accuracy is insufficient. In terms of finite element analysis, many CAD / CAE software companies, such as Ansys, Flux, SIMULIA, UGS, have developed multi-physical field couplingcomputing tools, which have been applied to aviation acoustics, magnetohydrodynamics, dynamic flow solid coupling and other fields, and the accuracy and efficiency of electromagnetic computing have gradually improved. Founded in 2007, InternationalJournal of Multi Physics magazine holds multiple coupling meetings every year, focusing on numerical models, model calculations, and experimental investigations, including multi-physical field analysis of motors.
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In the aspect of traditional multi-physical field coupling analysis, the alternating iteration method can effectively solve the weak coupling and periodic steady state strong coupling field problems, and the direct coupling method is the best way to analyze the transient strong coupling field problem. The initial multi-field coupling calculation is a sequential single-pass coupling iteration method, which is less computational, but is poor for not considering multi-field coupling. In view of the deficiency of single sequential coupling, the sequential coupling calculation method of the same model is proposed, which eliminates the process of two modeling times, but the coupling model of multiple physical fields is required to be consistent and reasonable, otherwise the gap in the calculation results is large, and the calculation amount is relatively large. At the same time, when analyzing the analysis of DC brushless motor with external circuit, the contradiction between the simulation step length and the calculation quantity in the nonlinear circuit analysis. It can be seen that due to the many coupling physical fields, complex coupling relationship and complex environmental boundary, the existing coupling field modeling and decoupling calculation methods need to be further improved.