A moving-coil linear generator with dual axial-magnetized stator for free-piston engines

Abstract

Free-piston engine coupled with linear generator is a new type of thermoelectric energy converter, which has the advantages of high efficiency and simple structure. In this paper, a novel moving-coil linear generator with dual axial-magnetized stator is proposed for this kind of short-stroke high frequency oscillation generating applications. Finite-element (FE) model of the generator is created, the static and transient characteristics are analyzed, and the losses in different components are compared. A full-bridge power converter is designed to meet the control requirements of reversible operation. A 540 W experimental prototype is developed and tested to validate the FE analysis. According to the tested and simulated results, the generator has advantages of high efficiency and fast response. The generating efficiency of 92% can be obtained at the rated generating power. The average inductance of the proposed generator is about 0.7 mH, which benefits from the low armature effect and ensures a very quick electromagnetic response.