A plasma torch converter based on the partial series resonant converter

Power converters for plasma torch applications generally operate at power levels above 30 kW, and hard switching topologies are normally used. The switching frequency at these power levels are restricted due to high switching losses and the unavailability of suitable high power transformers. While significant progress has been made in recent years in soft switching by using resonant techniques, the applications have been restricted mostly to low power applications. The zero voltage switching partial series resonant power converter has properties that make its application at high power levels attractive. In this paper, such a power 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. Experimental results are presented on a 30 kW, 40 kHz, DC plasma torch converter using an IGBT partial series resonant converter