A Hybrid dc-to-ac Polyphase Variable Frequency Converter

A method to combine a thyristor switch with a rubbing contact distributor in order to produce a polyphase square-wave output from a dc supply is described. The switch operates sequentially on each phase and is rated at a fraction of the total output of the converter. An experimental converter was used to study the problems of transferring the static switch from phase to phase without sparking under various loading conditions. A successful 6-kW laboratory converter was evolved, capable of operation on inductive and resistive load from 50-Hz to zero output frequency with a high efficiency. The economic features of the system and its application are discussed.