Low Harmonic Design And Analysis Of FSCW-PMM Based On Magnetic Field Modulation Theory

Electric vehicles have the advantages of energy saving,environmental protection,high efficiency,and low noise,which is one of the effective means to protect the environment and promote green development.Drive motors for electric vehicles should have the characteristics of large output torque,high efficiency,and high power density.Compared with other motors,fractional slot concentrated winding permanent magnet machine(FSCW-PMM)is widely applied in electric vehicles,aerospace and wind turbine due to its merits of high copper filling factor,low cogging torque,high output torque and high efficiency.The main disadvantage of this motor is the high harmonic content in the air-gap flux density of armature reaction magnetic field(ARMF)of the FSCW-PMM,which lead to large loss,local core saturation,acoustic noise and vibration.The air-gap flux density of ARMF and permanent magnet field of the 36-slot/42-pole FSCW-PMM is analyzed on the basis of the theory of magnetic field modulation.Then,a low harmonic design method using double windings is proposed and a 36-slot/42-pole double winding low harmonic permanent magnet machine(DWLH-PMM)topology is established.Systematic research is carried out on the topology,harmonic cancellation theory,structural parameter design,electromagnetic performance simulation,prototype production and expermantal testing.The main research content of this article are as follows:Firstly,the magnetomotive force(MMF)of single-phase and three-phase winding are discussed based on the theory of FSCW.Combining magnetic field modulation theory,the MMF permeance model of 36-slot/42-pole FSCW-PMM is established by the equivalent magnetic circuit method,and the air-gap flux density of ARMF and PM field and its harmonic formula are derived.The model of 36-slot/42-pole FSCW-PMM is established by using finite element software and the accuracy and rationality of the theoretical derivation are verified.Secondly,based on the analysis of the 36-slot/42-pole FSCW-PMM,a low harmonic design method with double winding is proposed,and a 36-slot/42-pole DWLH-PMM is established.Also,the design steps and the principle of harmonic cancellation are explained.The power and torque equations of the DWLH-PMM are derived,the main parameters are optimized on this basis,and the motor structure parameters are finally determined.Thirdly,the air-gap flux density of ARMF,cogging torque,PM flux linkage,no-load induced electromotive force,inductance and output torque of the36-slot/42-pole DWLH-PMM are analyzed by using finite element analysis.Also,the performance are compared with the 36-slot/42-pole FSCW-PMM.Then,the loss of above two motors are calculated,mainly including the loss of stator and rotor core,copper loss of each winding and eddy current loss of permanent magnet on load.According to various loss results and output power,the efficiency of two motors are obtained.Finally,based on the analysis of the above content,the prototype of DWLH-PMM is manufactured according to the optimized dimensional parameters of36-slot/42-pole DWLH-PMM.A semi-physical experimental platform based on d SPACE is established to test the prototype,and the experimental values are compared and analyzed with the simulated values to verify the correctness of the prototype.