A Plate Moving-Magnet Linear Generator Designed for Free-Piston Engines

Free-piston engine coupled with linear generator is a research hotspot in the field of novel vehicle mounted power generation devices. A plate moving-magnet linear generator (PMMLG) is proposed and designed for free-piston engines in this paper. Magnetic circuit of the novel linear generator is analyzed and modeled in detail. The dimensions of a 2 kW prototype with the max stroke of 40 mm and the max electromagnetic force of 800 N is designed by using the derived magnetic circuit model. Static and transient electromagnetic field finite element models with motion solvers are created. Magnetic field distribution, electromagnetic force characteristics, EMF characteristics, coil inductance, generating power and losses of the linear generator are analyzed and compared with two reported prototypes. Computational fluid dynamics model of the PMMLG is established, and the temperature field is analyzed to verify that the air-cooling conditions can ensure long-term stable running of the linear generator without demagnetization. The research results show that the linear generator has the characteristics of low moving mass, low cogging force, high generating efficiency and high response speed.