IGBT device application aspects for 50-kW zero-current-transition inverters

The operational conditions and behaviors of semiconductor devices in soft-switching inverters are quite different from those in conventional hard-switching inverters; this has significant impact on the design optimization. This paper addresses two application aspects of insulated gate bipolar transistor (IGBT) devices for two different types of three-phase zero-current-transition (ZCT) soft-switching inverters, which are built with 50-kW power rating for electric vehicles traction motor drives. One aspect is the characterization of main IGBTs under different ZCT conditions, for which switching loss reductions are quantified, and variations of soft-switching behaviors and mechanisms under different resonant tank designs are investigated and compared. The other is the selection and characterization of auxiliary switches. From the analysis on the unique nonconventional operation conditions of the auxiliary switches, it is concluded that the current ratings specified for commercial IGBTs cannot meet the requirements for the auxiliary switches. Accordingly, methods to select and characterize suitable auxiliary switches are proposed, and IGBTs from different manufacturers are tested and compared using the proposed methods. Hardware implementation and experimental results of the 50-kW prototypes are provided.