Analysis and Experimental Verification of Detent Force and Static Thrust of a 3 kW Single-phase Linear Permanent Magnet Generator for Free-piston Stirling Engines

Linear generators are used in free-piston Stirling engines (FPSE) because of their reciprocating mechanism. In the FPSE, the generator is driven using the motor mode to drive the engine. Once the engine begins to operate, the generator mode is used. For this reason, a single-phase linear permanent magnet generator (SPLPMG) suitable for the reciprocating motion of a mechanism-driven type and a simple initial driving operation is applied to a Stirling engine. However, compared with rotating machines, it is not as easy to evaluate the detent force and output power of a linear permanent magnet generator. It is particularly important to evaluate the former because the generator includes a permanent magnet. To analyze the characteristics of the linear generator, the detent force and static thrust were analyzed using finite element analyses. In addition, the composition and evaluation methods of the test rig for evaluating the detent force and static thrust are proposed. Finally, the evaluated static thrust was converted into an output and compared with the analytical results. Findings confirmed that the finite-element and experimental results of the proposed method were similar.