Three-phase Permanent Magnet Switching Flux Motor Field Weakening

With the development of the modern power electronics, computer aided system and microcomputer control techniques, problems on the design and control of permanent magnet machines with doubly salient structure have been solved effectively. The machines exhibit advantages such as simple structure, good robust character, high power desity and high output torque capability. As the optimal design techniques and control strategies are continuously presented, the marketization of these machines is expected to be realized and extended among those doubly salient machines. The permanent magnet flux-switching machine (PMFSM) studied in this paper is a good candidate which has good operation performance and flux-weakening capability.In this thesis, the development of the doubly salient permanent magnet (DSPM) machine is discussed to show how PMFSM was developed. Speed regulating systems and flux-weakening control application situations are then presented in detail. Meanwhile, the advantage of PMFSM in the field of flux-weakening is illustrated. Them the basic principles of flux-weakening of the permanent magnet synchronous machine (PMSM), DSPM machine and PMFSM are studied, showing that the techniques for the PMSM is compactible to the BLAC operation. Parameters such as rotor pole height and width which have effects on the operation performance and d-axis inductance as well as flux-weakening capability are analysed with both qualitative magnetic circuit analysis and quantitative finite element analysis (FEA), the direction for optimal design considering flux-weakening application is also defined. And, based on the study, the operation performance and flux-weakening capability of the three-phase 6/4, 6/5, 12/10-pole PMFSMs are compared. The comparison shows that the 6/5-pole PMFSM has better advantage over the other two types in speed extension. Furthermore, the measured inductances (both static and in flux-weakening mode) and actual flux-weakening capability are compared with the simulation results, showing good agreements. It is shown that the speed extension of the prototype is up to 11.6 times which is far beyond the traditional permanent magent motors. And through the comparison of simulating and experimental results, what must be paid enough attention is that the small deviation in d-axis inductance will casue unacceptable deviation in calculating the speed extension.