Surge Current Interruption Capability and Failure Mechanisms of Discrete IGBTs Under Hard and Soft Switching in Hybrid DC Circuit Breakers

Hybrid circuit breakers (HCBs) represent a new generation of circuit breakers that combine the advantages of mechanical breakers (MBs) and solid-state circuit breakers (SSCBs), offering fast interruption speeds and low on-state losses without requiring cooling. However, their adoption remains limited due to the high cost of semiconductors. This paper investigates the surge current capability and failure dynamics of discrete insulated-gate bipolar transistors (IGBTs), a critical component in HCBs. The study employs a gate voltage of 50V to drive the IGBT, evaluating its surge current capability under controlled conditions by varying three parameters: the voltage derivative (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dV /dt</i>), the current derivative (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">di/dt</i>), and the case temperature. Results show that a single discrete IGBT rated for 110A can conduct and turn off surge currents up to 1400A, which is nearly 13 times its nominal current, under hard switching conditions. Under soft switching conditions, the surge current interruption capability increases from 1400Ato 1600A, representing a 14%improvement, while the turn-off energy losses are reduced by 40%. Itwas also shown that at such high peak turn-off currents, device failure was associated with gate voltage oscillations during turn-off, primarily caused by elevated junction temperatures. Additionally, reducing the system inductance from 29 µHto 15 µH decreased the energy absorption capability by 50%, highlighting the importance of incorporating a dedicated inductor in low-inductance systems. These findings underscore key design considerations for enhancing the reliability and performance of cost-effective hybrid circuit breakers.