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Advanced Controller Developed for the Free-Piston Stirling ConvertorA free-piston Stirling power convertor is being considered as an advanced power-conversion technology for future NASA deep-space missions requiring long-life radioisotope power systems. The NASA Glenn Research Center has identified key areas where advanced technologies can enhance the capability of Stirling energy-conversion systems. One of these is power electronic controls. Current power-conversion technology for Glenn-tested Stirling systems consists of an engine-driven linear alternator generating an alternating-current voltage controlled by a tuning-capacitor-based alternating-current peak voltage load controller. The tuning capacitor keeps the internal alternator electromotive force (EMF) in phase with its respective current (i.e., passive power factor correction). The alternator EMF is related to the piston velocity, which must be kept in phase with the alternator current in order to achieve stable operation. This tuning capacitor, which adds volume and mass to the overall Stirling convertor, can be eliminated if the controller can actively drive the magnitude and phase of the alternator current.
Document ID
Acquisition Source
Glenn Research Center
Document Type
Gerber, Scott S.
(ZIN Technologies, Inc. Brook Park, OH, United States)
Date Acquired
September 7, 2013
Publication Date
June 1, 2005
Publication Information
Publication: Research and Technology 2004
Subject Category
Spacecraft Propulsion And Power
Distribution Limits
Work of the US Gov. Public Use Permitted.
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