Electromagnetic Design And Analysis Of Primary Permanent Magnet Linear Motor Based On Halbach Distribution

At present,the domestic requirements for the performance of rail transit equipment continue to increase,and linear motor-driven rail transit systems with high efficiency,low emissions and low pollution have been vigorously developed.However,with the emergence of various situations such as the increase in traffic itinerary,how to ensure that the linear motor still has greater thrust and better stability under the conditions of large air gap is a hot research topic.In this paper,the Halbach permanent magnet array structure is applied on the basis of the new structure motor-magnetic barrier coupling primary permanent magnet unilateral excitation linear motor(MBCPPMUELM),and three optimization methods are adopted to fully improve the thrust of the linear motor under the conditions of large air gap and long stroke.The problem of insufficiency makes linear motors have a broader application prospect in long-distance rail transit systems.Firstly,the research significance of this subject,a new structure motor and Halbach permanent magnet array are proposed.The advantages and disadvantages of linear induction motors,linear switched reluctance motors and permanent magnet linear motors used in rail transit drive systems are analyzed and summarized.The new MBCPPMUELM can better solve the problems faced by the above three motors in this field.Finally,the principle,research status and types of Halbach permanent magnet arrays are summarized,and the magnetic barrier coupling primary permanent magnet unilateral excitation linear motor(H-MBCPPMUELM)based on Halbach distribution is proposed in this paper.Secondly,introduce the structure and working principle of H-MBCPPMUELM.Considering the number of permanent magnet pole pairs,the number of secondary magnetic barrier protruding teeth,and the winding factor and air gap magnetic density harmonic content under 20 matching schemes,the appropriate number of poles is determined.Thirdly,analyze and calculate the magnetic field of the motor.According to the material properties,H-MBCPPMUELM is divided into three parts: air gap subdomain,permanent magnet subdomain and primary stator slot subdomain.The expression of each subdomain is obtained from Poisson equation,Laplace equation and Fourier formula;based on The magnetomotive force permeance model of the motor analyzes the air gap flux density of H-MBCPPMUELM.Through derivation,the thrust and power expressions of H-MBCPPMUELM are obtained,the key structural parameters that affect the thrust of the motor are clarified,and the electromagnetic design scheme of H-MBCPPMUELM is determined.Finally,on the basis of theoretical analysis,analyze the combination of four Halbach permanent magnet arrays,use finite element software to analyze the influence of each combination on the electromagnetic performance of 18/20H-MBCPPMUELM,and determine the Halbach permanent magnet suitable for 18/20H-MBCPPMUELM Array.Carry out the optimization of the motor modulation ratio,the number of slot poles and the optimization of the additional magnetic block of the primary iron core yoke,compare and analyze the electromagnetic performance parameters under the three optimization schemes,and determine the optimal modulation ratio range of the motor,the number of slot poles matching scheme and additional Magnetic block size.After the overall optimization,the thrust of the four types of H-MBCPPMLM is increased by more than 12% compared with MBCPPMLM,and the thrust pulsation is reduced by more than 20% compared with that before optimization.This proves the feasibility of the optimization method.It is a primary permanent magnet for magnetic barrier coupling.The further promotion of linear motors provides a reference.