Method for reducing cogging force by optimization of the pole arc in permanent magnet linear motors

QUAN Lei， FAN Chengzhi， YE Yunyue
（College of Electrical Engineering， Zhejiang University， Hangzhou 310027， China）

Abstract：Force ripple caused by cogging force is one of the main reasons which prevent permanent magnet motors from acquiring high performance. Aiming at reducing cogging force in permanent magnet linear motors， taking into account of the structural features of linear motors， an analytical method based on energy method and Fourier series was proposed to obtain the expression of cogging force which was related with polearc. End force， which was closely related with the length change of the secondary rod， can also cause force ripple，  a method based on different combinations of polearc for reducing cogging torque was proposed  to avoid excessive length change of the secondary rod. Simulation and experiment results show that the method can be effective to reduce cogging force and improve the motion performance of the permanent magnet synchronous linear motors.
Key words：permanent magnet linear motor; cogging force; polearc; finite element method; static magnetic field