Novel topology for parallel connection of soft switching, high power, high frequency inverters

Inductive heating applications like pipe welding or steel strip annealing require electrical power ratings of several MWs at frequencies up to 100 kHz and higher. The large power-frequency product represents a significant challenge for today´s semiconductor technology. As the absolute maximum rating of a single stage inverter is often far below rated power, several inverters or several devices have to be connected in parallel. This paper presents a novel topology, consisting of parallel connected soft-switching high-frequency inverters. Distinctive features include flexible configurations, negligible shunt currents between inverters, and equally shared power among inverters. Furthermore, compared to a single-inverter-system, no additional reactive components are necessary for connecting inverters in parallel and there is no need of a high frequency transformer to adapt the impedance of the load to the inverters.