Basic Research On Axial-field Switched Flux Memory Machine

The traditional permanent magnet sychrounous machines(PMSMs)employ high-energy-product neodymium-iron-boron permanent magnet(NdFeB).However,the constant magnetic field produced by NdFeB makes air-gap flux in PMSM non-adjustable.Thus,it is difficult for conventional PMSMs to achieve high output torque in constant torque region,and wide speed operation in constant power region simultaneously.As a result,the industrial application of conventional PMSMs is inevitably limited.Memory machine(MM),which employs low coercivity PM,emerged as required.It can achieve efficient online flux-adjustment by applying a temporary magnetizing or demagnetizing current pulse to vary the magnetization state of the PM.These advantages make MM become promising for many applications.Based on the review on the state-of-art of MMs and axial field machines(AFMs),three novel topologies of axial field switched flux memory machines(AFSFMMs)are proposed by combining the advantages of switched flux MMs and AFMs.The AFSFMMs exhibit the merits of energy-efficient flux regulation,wide speed range and high torque density.This thesis establishes basic studies on the proposed AFSFMMs in terms of their diverse topologies,working principle,electromagnetic characteristics,mathematical modeling as well as control method.The main research works include several aspects,which can be summarized as follows:(1)The flux-memory characteristics of low coercive force permanent magnet(e.g.AINiCo)are introduced,and the recent developments of MMs and AFMs are reviewed including the machine topologies and the operation principle.(2)Three novel topologies of AFSFMMs are proposed.Then,the structure characteristics,simplified magnetic circuit and operation principle of them are analyzed.(3)The models of three novel topologies are built.The electromagnetic characteruistics of the machines are numerically investigated and compared based on 3D finite element analysis(3D FEA).(4)A quasi 3D FEA is introduced so as to improve the calculation efficiency.Then,the quasi-3D and 3D FEA results,in terms of flux linkage,back-EMF and torque characteristics,are presented and compared,which verifies the correctness of the developed quasi-3D FEA.(5)The nonlinear mathematical model for the proposed AFSFMMs is built,and the simulation of the drive control system is conducted based on MATLAB/Simulink platform.Then,the on-load flux-regulation ability of the machines is verified on the MATLAB/Simulink platform.