A Novel Three-Phase Tubular Permanent Magnet Linear Generator for Free-Piston Stirling Engines

This article proposes an air-cored three-phase tubular permanent magnet linear generator (3P-TPMLG) with a novel free-piston Stirling engines (FPSEs) structure. First, the concrete construction and initial dimensions of the 3P-TPMLG are given through design principles and experience. Second, the mover’s basic working principle and operational process are discussed using relevant equations and the isolines distribution of magnetic vector potential at several typical mover positions. Third, the 2-D and 3-D machine models established by finite element analysis (FEA) software FLUX and electromagnetic field analysis are presented. Furthermore, two pivotal parameters are optimized to improve operating conditions and output performance of 3P-TPMLG. Finally, the output parameters of 3P-TPMLG are solved separately by FLUX under the constant and sinusoidal velocities. Following finite element dynamic simulation verification, 3P-TPMLG has good power output at both unchanged and sinusoidal velocities. Meanwhile, when the reciprocating frequency is 80 Hz, and the proportion of permanent magnet (PM) length in half pole pitch is 7/10, the comprehensive evaluation of the generator is optimal. The novel structural 3P-TPMLG for FPSEs can realize symmetrical three-phase power generation when the mover reciprocates linear motion at a sinusoidal velocity. Besides, the comparisons prove that the 3P-TPMLG has the advantages of high efficiency, high power generation density, and low construction price.