Lightweight Power-Conditioning System for Ion Engines Using Energy-Storage Transformers for Conversion, Nondissipative Regulation and Protection

Ion engines have been found to be demanding loads for high-voltage solid-state power-conditioning systems. This is due, in large part, to the tendency of these engines to undergo frequent and severe electrical arcing. The unusual ruggedness and efficiency requirements for such power systems are in direct conflict with the requirement for an extremely light weight. This paper describes a six-stage nondissipatively-regulated modular conversion system in which the use of an unconventional method for accomplishing dc-to-dc conversion, current-feedback base drive for the power transistors, and a relatively high (10 kc/s) intermediate conversion frequency results in an efficient and lightweight power-conditioning system with excellent protection characteristics. In this modular 2000-volt 1600-watt system, voltage conversion is accomplished by means of multiple-winding energy-storage transformers, each containing a core with an air gap. These transformers are caused to absorb energy from the source on one half cycle and to discharge energy into the output filter and load on the succeeding half cycle. This configuration makes possible a converter in which no semiconductor element is subjected to an immediate or abrupt transient as a result of a short circuit across the high-voltage output; protection schemes need not be elaborate. This "energy-pumping" conversion technique, in which the special energy-storage transformers perform multiple functions involving not only voltage conversion but also filtering, nondissipative regulation, and system protection, results in a system which is physically very simple.