A Linear Permanent Magnet Generator for a Free-Piston Energy Converter

This paper discusses the issues that are pertinent to the design of a linear permanent magnet generator for application in a free-piston energy converter. To achieve the required high power density, high efficiency and low moving mass, a tubular machine equipped with modular windings and quasi-Halbach magnetization is considered to be the most appropriate. Analytical expressions for predicting the open-circuit magnetic field distribution, emf, thrust force and armature reaction, as well as the selfand mutual inductances of the machine, are established and verified by finite element analysis. They provide an effective tool for design optimization. It is shown that the machine design can be optimized with respect to three key dimensional ratios while satisfying other performance specifications