Transient and steady-state performance of Space Power Research Engine with resistive/motor loads

This paper describes the results of tests carried out on the Space Power Research Engine (SPRE) developed as an advanced power convertor for space-based electrical power generation. The tests were performed at NASA Lewis Research Center LeRC, to evaluate the interaction and performance of a free-piston Stirling engine/linear alternator (FPSE/LA) feeding into either a resistive or small induction motor load. The test results showed that the control system could maintain constant voltage and stable periodic operation over a wide range of engine operating parameters and loads. Modest resistive load changes were shown to cause relatively large voltage and, therefore, piston and displacer amplitude excursions. Starting a typical, fractional horse-power induction motor yielded large and, in some cases, deleterious voltage transients. The steady-state and transient test results demonstrated the need for more effective controls for FPSE/LAs in stand-alone power systems, and can be used to validate analysis codes