SiC Based Solid State Circuit Breaker: Thermal Design and Analysis

Compared to conventional mechanical breakers, solid state circuit breakers (SSCBs) have superior advantages like ultra-fast fault clearing speed and arc-free current interruptions. SSCBs are thus increasingly applied in electric vehicle charging infrastructure (EVCI), electrified ships and aircrafts, and railway systems. With the advanced performance of silicon carbide (SiC) MOSFET power modules, the SiC based SSCBs are expected to achieve lower conduction losses and faster fault breaking speed in a smaller form factor. However, it is still a significant challenge for SiC based SSCBs to maintain operational device junction temperatures under all working conditions, especially the overload conditions with escalated thermal stresses that are typical routines for SSCBs. In this paper, the thermal performance of a SiC based SSCB prototype is experimentally evaluated under both the nominal load condition and overload conditions. Finite element models and thermal network models are constructed to estimate the overload withstand time of SSCB prototype under different ambient temperatures. Considering the popularity of the SiC MOSFET modules studied in this paper, the established overload evaluation strategy is applicable to not only SSCBs, but also power converters with high requirements on overload withstand capabilities.