Design of a linear magnetic-geared free-piston generator for series hybrid electric vehicles

The free-piston generator is an energy conversion device which integrates a combustion engine and a linear electrical generator into a single unit. Due to its benefits in simple structure, high efficiency and robustness, the free-piston generator is very suitable for application in series hybrid electric vehicles. This paper proposes a linear magnetic-geared machine for free-piston generator. It integrates a linear magnetic gear with a linear permanent magnet synchronous machine (PMSM), and can achieve a higher force density and power density than conventional linear machines. By using finite element method (FEM), the proposed machine is analyzed and verified.