Research on the Magnetic Characteristic of a Novel Transverse-Flux PM Linear Machine Used for Free-Piston Energy Converter

Free-piston energy converter, composed of a free-piston engine and a permanent-magnet (PM) linear machine, is a promising generator concept for series hybrid electric vehicles (HEVs). In this paper, a novel transverse-flux PM linear machine is investigated for such applications. Unlike conventional transverse-flux machines, the proposed machine features simple mechanical structure. Flux leakage of the proposed machine is analyzed, and parameters of the machine are optimized by finite-element method (FEM). Compared with conventional flux configurations, such as radial flux, axial flux and Halbach, the proposed transverse-flux topology showed advantages in low cogging force, low thrust fluctuation, and high efficiency. A prototype was designed and manufactured. Further experiments indicated satisfactory load characteristic of the machine.