No-Load Magnetic Field and Cogging Force Calculation in Linear Permanent-Magnet Synchronous Machines with Semiclosed Slots

This paper presents an improved analytical subdomain model for predicting the magnetic field in linear permanent magnet synchronous machines (LPMSMs) with semiclosed slots accounting for the finite length of primary iron core and secondary back-iron. The whole field domain is divided into eight subdomains and the magnetic field in each subdomain is solved by applying the variable separation method, adequate boundary conditions, and interface conditions. In this model, both the slot and end effects are considered. The thrust and normal forces are calculated by the Maxwell stress theory. The finite element analysis is carried out to validate the analytical model. Finally, an LPMSM prototype is manufactured and tested. The experimental results show that the developed analytical model has high accuracy for predicting the magnetic field and forces.