Precise estimation of dynamic junction temperature of SiC transistors for lifetime prediction of power modules used in three-phase inverters

Precise transient temperature measurement is fundamental to estimate lifetime of power modules, especially those made with SiC transistors having very low thermal capacitance. This paper shows a precise method to estimate dynamic temperature of SiC components composing a power module used in three-phase inverters. This method is based on the use of a fast thermal camera to precisely measure thermal impedance of each die. Results of thermal camera measurements are validated by comparison with classical on-state resistance measurements to estimate junction temperature. Thermal impedance model is then coupled with precise loss calculation in order to predict dynamic die temperature during operation in a three-phase inverter. Measurements of the temperature variation of SiC dies conducting typical currents of a 540 V/7.5 kW three-phase inverter for aeronautical applications show the accuracy of the developed model for dynamic junction temperature estimation.