Thermal and Electrical Stress Differences of SiC MOSFET Under Active/Reactive Loads in AC Power Cycling Test

Thermal and electrical stresses are key factors influencing the reliability of SiC MOSFETs. The alternating current (AC) power cycling test (PCT) has emerged as a more representative reliability test method for applications compared to traditional direct current (DC) PCT. However, the distinction between thermal and electrical stress under active and reactive load conditions during AC PCT remains largely unexplored. This paper presents a comparative study of active and reactive load AC PCT using a SiC inverter topology. Theoretical analysis and experimental verification show that under identical packaging and testing conditions, the differences in electrical stress (dv/dt at the gate and source, Vds overshoot) between the two loads are negligible. The difference in thermal stress between the two loads depends on the current and the modulation index. When an increased current causes the SiC MOSFET to enter synchronous rectification, the thermal stress on the active load exceeds that on the reactive load. Moreover, the higher the modulation index, the greater the difference in thermal stress. These findings support the design of endurance testing for SiC MOSFETs under AC PCT.