Study on force-angle characteristics of permanent magnet linear synchronous motor

XU Yaohui; ZHU Fuwen; GAO Caixia; ZHAO Baosen; WANG Han; MIAO Qingbin

doi:10.16186/j.cnki.1673-9787.2023060026

Abstract：Objectives The force angle characteristic is an important characteristic to analyze the operation stability of permanent magnet linear synchronous motor(PMLSM),and it is the basis of designing and con-trolling motor.The influence of armature resistance was generally ignored in the existing calculation of force angle characteristics.However,due to the influence of armature resistance at low speed,PMLSM force angle characteristic has obvious deviation phenomenon.Therefore,using the existing force angle characteris-tics to calculate the performance of PMLSM will have a large deviation,which cannot meet the actual work needs of the motor.Hence,in this paper,the basic reasons and critical conditions for the deviation were in-vestigated,and the critical conditions of the force angle characteristic offset were determined.Methods Firstly,an analytical model of PMLSM force angle characteristics considering armature resistance was es-tablished,and the reason for the deviation of force angle characteristics was analyzed.Secondly,based on the established analytical model,the influence of different factors on the force angle characteristics was studied by the peak thrust and its corresponding power angle,and the finite element model was established to verify the analysis results.Finally,the critical condition of PMLSM force angle characteristic offset was determined by analytical method.When the force angle offset coefficient k(k=Xt/Ra)is≥11.43,it can be approximated that the force angle corresponding to the peak thrust is equal to 90°,and the phenomenon of force angle offset can be ignored.The causes of the deviation of the force angle characteristic curve and the correctness of the critical conditions were verified by finite element simulation and experimental results verify.Results This study found that compared with the commonly used force angle characteristics that ig-nore armature resistance,the force angle characteristics of PMLSM are shifted to the left.The phenomenon of force angle characteristic deviation can lead to two effects.One is that the relationship between thrust and armature current is not monotonic,resulting in a phenomenon where the current of small loads is larger than that of large loads.The peak thrust decreases during low-frequency operation,so constant thrust operation cannot be maintained at low frequencies.Conclusions The research in this paper has important reference value for the design and precise control of PMLSM.