Soft switching three level inverter with passive snubber circuit (S3L inverter)

Presented here is a three level voltage source inverter for electric drives, uninterruptable power supplies and for mains feeds. Unlike the usual hard switching topologies, it is implemented as completely soft switching. A novel patented snubber circuit is added, which is structured very simply and consists of only a few passive components. This snubber circuit works in principle without any losses; all switching operations in the three level voltage source inverter are in principle free of switching losses. For this reason, very high values of switching frequency up to about 40 kHz, and very high efficiencies up to more than 98%, can be realized, even with utilization of economical standard IGBT´s. In particular with utilization of IGCT´s, an effective di/dt limitation is to be emphasized, which works without additional inductive voltage stressing of the IGCT´s.