This paper presents the influence of different pulse width modulation (PWM) methods on losses and thermal stresses in SiC power modules used in a three-phase inverter. The variation of PWM methods directly impacts instantaneous losses on these semiconductors, consequently resulting in junction temperature swing at the fundamental frequency of the converter’s output current. This thermal cycling can significantly reduce the lifetime of these components. In order to determine semiconductor losses, one needs to characterize SiC devices to calculate the instantaneous power. The characterization methodology of the devices, the calculation of instantaneous power and temperature of SiC dies, and the influence of the different PWM methods are presented. A 15-kVA inverter is built in order to obtain experimental results to confirm the characterization and loss calculation, and we show the best PWM methods to increase efficiency and reliability of the three-phase inverter for specific aircraft applications.

Accurate thermal cycle measurement is essential for estimating the lifetime of power modules, particularly those employing SiC MOSFETs characterized by extremely low thermal capacitance. This work presents a rigorous method for estimating the die temperature variation of SiC components within power modules utilized in three-phase inverters. The approach leverages high-speed thermal imaging to accurately characterize the individual thermal impedance of each die. The resulting thermal impedance model is coupled with high-fidelity loss calculations to predict dynamic SiC die temperatures during inverter operation. Experimental results obtained under conditions representative of a 540 V / 7.5 kW aeronautical inverter demonstrate the model's accuracy in tracking dynamic SiC die temperature variations.