Force Ripple Reduction Methods for Tubular Permanent Magnet Linear Machines

This paper presents some novel force ripple reducing techniques for tubular permanentmagnetlinear machines (TPMLMs) with the square-shaped cross section. These methods are verystraightforward, so their implementation in TPMLMs with the square cross section is easy. Ananalytical form of machine parameters such as the thrust force is obtained by solving the analyticalfield. A modular configuration for permanent-magnet pole is used to reduce teeth coggingforce. Furthermore, the manufacturing cost of TPMLMs can be reduced by using modular polepermanent-magnet. In this method, the width of permanent-magnets (PMs) is calculated by usingFourier analysis and a sensitivity analysis has been conducted to identify the robustness of thistechnique. Additional stator side methods are used to decrease the end face cogging force. Moreover,the stator teeth shifting method is proposed to reduce the electromagnetic force ripples. Also,the produced electromagnetic force of the machine is increased by using a delay in the power supply.3 -D non-linear finite-element analyses and experimental tests are performed to investigatethe effectiveness and performance of proposed techniques.