Research On The Key Techniques And Method Of Design For Permanent Magnet Synchronous Motors

With the outstanding advantage of high efficiency and energy saving, the rare-earth permanent magnet motor (REPMM) has great development potential and is widely used in national defense, aeronautics and astronautics, agricultural and industrial production and daily life and so forth. Because of the diversity and complexity of structure, the traditional design and analysis methods based on electrically excited motor are not suitable for REPMM. Meanwhile, in complicated operation conditions, motors by traditional design patterns usually cannot achieve performance as good as that in a constant condition. In order to meet the needs of development of high performance products, it is necessary to do innovative research on the REPMM design, by applying the theories in multi-subject and using modern designing techniques.Systematical studies were performed in this dissertation mainly on magnetic structure design, parameters calculation, performance analysis and optimization of permanent magnet synchronous motor (PMSM), combining with engineering practice. To overcome the flaws and shortcomings of the traditional motor design, a global integrated matching design concept and method based on customer requirement was proposed. The content of work in the dissertation was as followed,The mathematical model of sine wave and square wave PMSM were respectively established and the main performance characteristics were analyzed. On this basis, the key technical problems of PMSM design were proposed, mainly embodied in four respects: design of rotor magnetic circuit structure, calculation and analysis of motor parameter and operation performance, optimal design technology, matching design of motor system in engineering application.Based on the equivalent magnetic circuit analysis, the calculating method of magnetic circuit coefficients was summarized. An approximate computation method was proposed to calculate the maximal permanent magnet area for magnetic flux per pole, and a comparison between several typical rotor structures was made. Taking as design cases, a low-speed high-torque PMSM, a PM Brushless DC motor and a line-start PMSM were proposed, and their rotor design features, main structure dimensions and calculating method of basic magnetic circuit parameters were analyzed.A systematical study was made on the PMSM performance analysis method based on numerical calculation of electromagnetic fields, including the construction of permanent magnet, the calculation of no-load and load magnetic field and the field-circuit coupling analysis. The focus of the research was on the application of Finite Element Method (FEM) in calculation of cogging torque, armature reaction reactance and synchronous reactance /inductance parameters. Transient and steady state characteristics of a line-start PMSM were analyzed by applying field-circuit coupled time-stepping FEM.The optimal design method of PMSM was studied, a field-circuit optimal design method was proposed on the basis of combined selectionof variable parameters, objective functions and constraint conditions. An optimal design for a line-start PMSM was made, and the influences of structure parameters on the motor performance were discussed.A novel global integrated matching motor design concept and method based on customer requirement was proposed, emphasizing the importance of regional performance analysis for motor design. A square wave PMSM for electric vehicle was designed, analyzed and optimized by applying the integrated matching design method, and prototype tests were carried out and verified the accuracy of the design and analysis.