Research On The Performance And Influence Factors Of Line Start Permanent Magnet Synchronous Motor

Compared with traditional induction motors,line start permanent magnet synchronous motor(LSPMSM)has the advantages of high power density,high power factor and high efficiency.Under the global background of increasingly tight energy resources,the research of LSPMSM becomes more and more important.In this paper,based on finite element method(FEM)and analytical method,the effects of winding turns,connection modes,voltage unbalance and high frequency harmonic voltage on the performance of LSPMSM are studied.Firstly,aiming at the optimal design of winding turns and winding connection modes in the design process of LSPMSM.using FEM and phasor method-the influence of winding turns and connection modes on the armature current,power factor,maximum torque,starting torque and losses of the LSPMSM are studied in depth and the influence mechanisms are discussed.It provides a theoretical basis for the design of winding turns and connection mode of LSPMSMSecondly,aiming at the common power quality problem of three-phase voltage unbalance in power grid,the steady-state and dynamic performance of LSPMSM under different degree of voltage unbalance are studied.The influence mechanisms of voltage unbalance on copper loss,stator iron loss and rotor eddy-current loss of LSPMSM are researched.Based on generation mechanism of electromagnetic torque,the harmonic torque components caused by positive-sequence voltage and negative-sequence voltage are analyzed,and the key factors affecting the torque ripple of LSPMSM are determined.Based on the analysis of the coupling effect between armature magnetic field,permanent magnet magnetic field and rotor winding magnetic field in starting process,the pulsating and constant torques with characteristic frequencies and magnitudes produced by the interaction of above magnetic fields are analyzed and determined.Based on the FEM,the variation laws of starting torque,minimum torque and critical moment of inertia under different degree of voltage unbalance are obtained,and the influence mechanism of voltage unbalance on starting performance is revealed.Finally,the influence of the high frequency harmonic component in the output voltage of the converter on the performance of the LSPMSM is investigated.Based on the analytical method,the coupling effect of time harmonic current and space harmonic magnetic field is deduced and obtained.The influence mechanism of high frequency harnonic on the loss of motor is analyzed.The research results provide a theoretical reference for the design of LSPMSM driven by frequency converter.