| Since the beginning of this century,the rapid developments of aerospace,electric vehicles and rail transit have promoted the development of machines in the direction of high torque density and high power density.Since the permanent magnets(PMs)and armature windings are located on the stator side of stator-PM flux-modulation(SPMFM)machines,it is easy to realize the thermal management of the PMs and windings,which is beneficial to improve the current density and thus the power density of machines.Therefore,this type of machine has potential development prospects in high-speed and high-power industrial applications.At present,domestic and foreign scholars have proposed a series of novel machine topologies to improve the torque density of SPMFM machines.However,the topology design of this type of machine is not yet perfect,and the torque density still has great potential for improvement.This paper reviews the existing literature on the SPMFM machines from the perspective of electromagnetic analysis method and topology research.Three main types of analysis methods are summarized: the method based on subdomain model,the method based on lumped parameter magnetic circuit model and the method based on magnetomotive force(MMF)-permeance model.The development history of doubly-salient PM machines,flux-switching PM machines,and flux reversal PM machines is mainly introduced.The main derivative structures based on the three basic topologies proposed by academia in order to improve the torque density and reduce the torque ripple are presented,and it is pointed out that main way of topology evolution is to optimize the PM MMF unit,stator permeance unit and armature MMF unit.The thesis systematically studies the analytical and topology construction methods of SPMFM machines,and puts forward a series of new topologies of high-torque-density SPMFM machines.The electromagnetic performance is analyzed and verified by means of analytical derivation,finite element analysis(FEA)and experimental test.The phased research contributions are as follows:(1)A method for quantitative analysis of flux modulation effects,which is based on air-gap power flow,is proposed.Then,the reasons for limited torque density of SPMFM machines are pointed out and the methods for improving the torque density are proposed.For the functional units of SPMFM machines,the topology construction methods of multi-harmonic PM MMF unit,PM MMF unit of multi-excited sources(MES),multi-harmonic stator permeance unit,and unconventional armature MMF unit are proposed.Two methods for constructing multi-harmonic topology are expounded: direct superposition method and indirect construction method.(2)Based on the construction methods of SPMFM machine functional units,the multi-harmonic single-excited source(SES)SPMFM machine is proposed,and its two basic topologies are introduced: surface-mounted multi-harmonic SES(SMMH-SES)SPMFM machine and consequent-pole multi-harmonic SES(CPMH-SES)SPMFM machine.Based on the analysis of the basic working principle,the electromagnetic performance of the above two machines is analyzed,and the influence of the main design parameters on the torque performance is studied.It is pointed out that the back electromotive force(EMF),torque and PM utilization of SMMH-SES SPMFM machine are higher than those of asymmetric-stator-pole flux reversal PM machine.A CPMH-SES SPMFM prototype has been manufactured and tested.Compared with the conventional consequent-pole flux reversal PM machine,the torque density of CPMH-SES SPMFM machine is increased by 55%.(3)Based on the construction methods of MES topology,the MES SPMFM machine is proposed,and its two basic topologies are introduced: consequent-pole MES(CP-MES)SPMFM machine and multi-tooth MES(MT-MES)SPMFM machine.On the basis of expounding the basic working principle,the electromagnetic performance of the two machines is analyzed,and the influence of the main design parameters on the torque performance is also studied.Compared with the conventional consequent-pole flux-switching PM machine,the torque density of CP-MES SPMFM machine is increased by 18% by directionally enhancing the amplitude of main working equivalent MMF harmonic.A MT-MES SPMFM prototype has been fabricated and tested.Compared with the conventional multi-tooth flux-switching PM machine,the torque density of the MT-MES SPMFM machine is increased by 30%.To sum up,this paper proposes a quantitative analysis method of flux modulation effects based on air-gap power flow,and based on this,torque density improvement strategies for SPMFM machines are proposed.Four kinds of high-torque-density SPMFM machines are proposed,and the torque density advantages of these topologies are verified by FEA and prototype experiments. |
