HV-IGBT drives and their applications

Universal in low voltage inverters and widely in use for a decade, the IGBT (insulated gate bipolar transistor) has proven its reliability in numerous applications. The one drawback is the limitation in output power achievable at these low voltages. Series connection of low voltage IGBTs to achieve higher output voltages is not an elegant and practical solution due to the problem of absolutely simultaneous switching necessary for safe operation. The recent introduction of HV-IGBTs (high-voltage IGBT) has finally made it possible to build the medium voltage drive up to 6.6 kV. HV IGBTs presently in use have a blocking voltage rating of 3300 V at 1200 A and devices of 6500 V at 600 A will be available in the near future. The standard three-level inverter output voltage of 2.3 kV can be realised with only one element whereas output voltages of 3.3 kV and 4.16 kV are realised with two elements in series. Some of the applications include rubber industry, ship propulsion, chemical and metals industries.