A Reduced-order Subdomain Analytical Model For Magnetic Field Of Surfacemounted Permanent Magnet Synchronous Motor

Surface-mounted permanent magnet motor(SMPM)is widely used in many aspects of production and life because of its simple structure,high efficiency and high torque density.The calculation of no-load magnetic field and armature reaction field of SMPM is the precondition of accurate prediction of back-EMF,cogging torque,noise and vibration,and affects the design and performance analysis of permanent magnet synchronous motor.This paper studies the application of subdomain method in magnetic field of SMPM,gives the general process of subdomain division,Poisson’s equation establishment,boundary condition and differential equation solution,and analyzes the relationship between the dimension of the equation and the number of poles and slots and harmonic order.A reduced-order subdomain analytical method for calculating no-load magnetic field of SMPM is presented.The permeability model of single-slot motor is established and the relationship between the single-slot permeability model and the whole magnetic field of the motor is determined.Based on the subdomain method,the magnetic field distribution of single-slot and slotless motor is obtained,and the magnetic field distribution of single-slot motor is superposed by phase.Finally,the superposed magnetic field is combined with magnetic field of slotless model to obtain no-load magnetic field in air gap of motor and reduced order of coefficient matrix.The correctness and reliability of the method are proved by comparing the analytical results with the finite element method(FEM)results.The paper proposes a synthesis method of armature reaction field for SMPM.According to the symmetry of the armature field under single-slot excitation,the entire motor region is reduced to a single-slot model possessing corresponding boundary conditions.According to the additional boundary conditions and the first and second boundary conditions of the magnetic field,the magnetic field distribution of the singleslot motor is obtained by subdomain method,and the armature reaction field is synthesized and reduced order of coefficient matrix.This method can be applied to the SMPM with single layer(SL)winding,up-down double layer(DL)winding and leftright double layer(DL)winding.Finally,the results of FEM and experiment verify the feasibility and correctness of the method.In this paper,reduced-order subdomain analytical method for calculating no-load magnetic field and armature reaction field of SMPM is proposed,which has important reference significance for the magnetic field analysis method and motor optimization design.