Fundamental Research On Dual-Consequent-Pole Transverse Flux Permanent Magnet Motor

In the traditional radial flux machine and axial flux machine,the competition of motor space is quite serious between the winding slot area and the tooth area which is corresponded to the electrical load and the magnetic load in the motor.To overcome that issue and improve the torque density of motor further,the transverse flux motors(TFMs)leap to the eyes of scholars all over the world.Since the relative decoupling between the electrical load and magnetic load in the motor space,the TFMs always benefit from the advantages of high torque density and high modularization.With those superiorities,TFMs are attractive in the direct-drive applications where high torque and low speed are always required,e.g.,electrical vehicle electrical boat and wind turbine generator systems.In this paper,based on the summarizing of the existed TFM technologies at home and abroad,a novel transverse flux machine is proposed to improve the torque density and space utilization further,which is named as dual-consequent-pole transverse flux permanent magnet motor(DCP-TFM).In this paper,the novel DCP-TFM and its related electromagnetic characteristics are listed as the research objects.The research works about mathematical modeling,electromagnetic designing,torque characteristic analysis,and electromagnetic performances analysis are carried out,respectively.Firstly,the basic topology configuration of DCP-TFM is introduced detailed,which is based on the development and evolution from some typical TFM topologies.The three-dimensional equivalent magnetic circuit model is built based on the analysis about the flux distribution characteristic.Then the simplification work is down to simply the three-dimensional magnetic circuit into a two-dimensional one which is composed with the circuit elements corresponded to the radial flux planes and the axial flux planes.And the subdomain method is quoted here to calculate the gap flux density distribution which is later used for the calculation of the circuit elements in the magnetic circuit.The computing methods of electromagnetic performances e.g.,PM flux linkage,no-load back electromotive force,cogging torque and electromagnetic torque are introduced based on the combination of equivalent magnetic circuit and subdomain method,in which the saturation effect and axial-end effect are both considered during the calculation process.The mathematical model of DCP-TFM which includes voltage balance equation and torque balance equation is introduced,providing the theoretical foundation of upcoming sections.Secondly,the electromagnetic design method of DCP-TFM is investigated.The main-size formula is deduced analogous to the traditional permanent magnet synchronous motors,which relates the torque with the motor sizes.Then the influences of basic structural parameters(e.g.,pole-pitch,thicknesses of PMs,pole-arc coefficients of PMs and axial tooth to slot ratio)on the torque density are discussed,and value range of those parameters are introduced which are selected to improve the torque density.The design process of DCP-TFM is summarized for a reference of the future designers.A prototype is designed and manufactured for verification.Thirdly,the torque characteristics of DCP-TFM are investigated.The PM flux distribution characteristics are presented to explain the improvement principle of the torque density from DCP-TFM to traditional TFMs.The torque performance,e.g.,cogging torque,static electromagnetic torque and electromagnetic torque are discussed by three-dimensional finite element method.The influences of structure parameters on cogging torque is investigated.The applicability of traditional cogging torque reduction methods on the novel DCP-TFM is discussed,and the influences of the average and torque ripple are also analyzed during the reduction of the cogging torque.Finally,the electromagnetic performances of DCP-TFM are investigated.According to the numerical calculation about the PM flux and phase inductance,the feature of the power factor in the novel DCP-TFM are explained.The influences of structure parameters and phase current control method on the power factor are discussed,respectively.Then,the changing laws of flux density in the cores and PMs of DCP-TFM are analyzed by three-dimensional finite element method.According to the foregoing flux density changing laws,the iron loss distribution law in the cores and the eddy loss distribution law in the PMs are discussed,respectively.The influence of phase current amplitude,rotation speed and materials of cores are also investigated.According to the computed loss results,the efficiency under different conditions are calculated,which provides a theoretical reference for the future engineering applications of DCP-TFM.