LAUSR

The rapid development of DC power systems in applications such as electric aircraft and microgrids has highlighted the need for high‐performance DC short‐circuit protection. Solid‐state circuit breakers (SSCBs), utilising power semiconductor devices, offer superior performance compared to traditional mechanical circuit breakers by providing fast arc‐free interruption and improved reliability. Whereas silicon carbide (SiC) MOSFETs and silicon (Si) insulated‐gate bipolar transistors (IGBTs) are widely used in these applications, their overcurrent capabilities and long‐term reliability under repetitive operation remain critical research topics. This paper investigates the overcurrent capability of SiC MOSFETs and Si IGBTs and analyzes their degradation mechanisms under repetitive overcurrent cycling. Experimental results show that although the SiC MOSFET has a longer overcurrent withstand time due to its saturation characteristics, it suffers from more severe ageing behaviours. Its gate‐source voltage ( V GS ) was found to drop by 3.3 V, its saturation current ( I sat ) dropped by 45.2 A, and its on‐state voltage drop significantly increased as the number of cycles reached 250. In contrast, the Si IGBT exhibited minimal degradation in its dynamic performance under the same conditions. To understand the underlying physics of these behaviours, detailed TCAD simulation models were developed based on the real device structures. Simulations revealed a single, concentrated hotspot in the SiC MOSFET near the gate, reaching a peak temperature of ∼1000 K. The Si IGBT, however, presented two distinct hotspots: one near the gate and another near the interface between the buffer and drift regions. We propose that this distributed thermal profile in the IGBT mitigates localised stress, which explains its superior long‐term reliability. Conversely, the high concentration of thermal stress in the SiC MOSFET's gate region leads to its severe ageing.