Monitoring of age-relevant parameters in an integrated inverter system for electrical drives based on SiC-BJTs

The Silicon Carbide Bipolar Transistor is a device that is barely brought into real application so far. It features very low conduction losses and a high power density. The application is in some points different and unusual in comparison to the mainstream power semiconductors as IGBTs or MOSFETs. The Silicon Carbide Bipolar Transistor, the SiC-BJT, is a current driven device and the effort in driving is uncommonly high. As an outcome of the present work it can be said that it is more like a shift of requirements from the power semiconductor power unit to the driver stage. With consideration of all system losses, including driving losses, the final unoptimized COSIVU prototype inverter system gained an increase of efficiency of 40-60% in comparison to the IGBT-based reference system dependent on the applied load points. In terms of reliability and possible failure modes, the SiC-BJT behaves differently from the mainstream devices. One result of the project is that the chips itself are quite robust but the packaging needs some improvements. Thermal impedance spectroscopy is a method for detecting possible deterioration in the cooling path of a device. A method for temperature estimation of the SiC-BJT during on-state will be presented in this work. The electronic hardware for thermal impedance spectroscopy has been developed to do the measurements in a non-laboratory setup in the inverter in real application. Furthermore, the hardware implementation was realized on a very small space for integration into an in-wheel motor inverter system.