A plasma torch converter based on the partial series resonant converter

Converters for plasma torches generally operate at power levels above 30 kW, and hard switching topologies are normally used. The switching frequency at these power levels is restricted due to high switching losses and the unavailability of suitable high power transformers. While significant progress was made in soft switching by using resonant techniques, the applications were restricted mostly to lower power applications. The zero voltage switching partial series resonant converter has properties that make the application at high power levels attractive. In this paper the converter is applied to a plasma torch application where power levels can go up into the megawatt range. To increase the power rating per unit, a distributed transformer and parallel operation of a number of converters are proposed. An improved dynamic controller is introduced and experimental results are presented on a 30 kW, 40 kHz, DC plasma torch converter using an IGBT partial series resonant converter.