Characteristic Analysis For Permanent-Magnet Linear Synchronous Motor Using MEC Model

Permanent magnet linear synchronous motors(PMLSMs)are widely used in industrial applications due to unique linear motion,high force density and high efficiency.The disconnection of the linear motor iron core causes magnetic field distortion,three-phase flux asymmetry,detent force and so on.Therefore,the analysis of the characteristics and magnetic field distribution are the basis of the design and analyses of linear motor.The FEA,as a common method,is very accurate,but it is time-consuming.The FEA is not suitable for the linear motor in the early stage of the design and optimization design.The magnetic equivalent circuit(MEC)method is an effective approach,which can well coordinate the problem between the analysis accuracy and the consuming time.This paper presents a relatively simple and accurate analytical model based on MEC to analyze the characteristics of PMLSM.The 2D FEA is used to verify the validity of the analytical model.In addition to the ends of PMLSM,the fluxes flowing through the each primary tooth are defined as four magnetic paths.The changes of the parameter values of four flux paths for only one primary tooth in range of a pole pitch movement are first solved.Then the corresponding parameters of all primary teeth can be obtained at any moment.The leakage fluxes are considered independently not into the network between magnets.This can reduce the number of the branches of the network.The structure of the equivalent magnetic circuit network model is kept fixed during motion,so the establishment and solution of the network model is relatively simple.This paper presents the structure of the network and the solution of the model parameters at a specific location firstly.Then,the model of the PM leakage,the periodicity of parameters in relative motion and the MEC model of end fringing field are emphasized.The solving process of the model is also given.The paper introduces the basic principle of the finite element method(FEM).The static model and transient model of PMLSM are established by FEM.The distribution of the magnetic flux density is obtained in static model.The detent force of PMLSM is obtained in transient model and the cogging force for one primary tooth is further solved.To obtain the end force,the model with non-slot is established.The flux linkages and the back electromotive force(EMF)are also solved.The paper presents the method to solve the characteristics of PMLSM based on the distribution of the magnetic through solving the analytical model.The 2D FEA is used to verify the validity of the analytical model.It can be concluded that the results obtained by two methods are almost consistent and the present analytical model is right.The reason of the error between two results is further analyzed.