A Tubular PM Linear Generator With a Coreless Moving-Coil for Free-Piston Engines

Free-piston engine coupled with linear generator is a new kind of thermoelectric energy converter. It has been highly concerned due to its high efficiency and low emission in recent years. In this paper, a tubular moving-coil linear generator is developed for the application of free-piston engines. The two-dimensional finite-element model of the linear generator is established, and its electromagnetic characteristics are analyzed. A power converter is designed to control the operating state and the electric current of the linear generator. A prototype is developed and used in a free-piston engine with a bore of 102 mm, and the main performance parameters are tested. According to the simulated and tested results, the linear generator can realize the stable running of free-piston engines. The peak power of the linear generator in a cycle is about 16.77 kW, and the averaged generating power of a cycle is 3.37 kW at the working frequency of 10 Hz. The generating efficiency at peak power of a cycle is about 95.2%, the averaged generating efficiency of a cycle is about 87.5%.