High-current Cryogenic DC Solid-State Circuit Breaker for Electric Aircraft

Cryogenic and superconducting technologies have great potential to significantly enhance the power density and efficiency of electric propulsion aircraft. However, fault protection in on-board DC power networks presents serious challenges, primarily due to the rapid rise and high magnitude of fault currents resulting from the low impedance of closely coupled networks. Furthermore, designing and selecting power electronic devices capable of operating at cryogenic temperatures introduces additional challenges. This paper presents the design of a 300 V/1700 A DC solid-state circuit breaker (SSCB) operating at cryogenic temperatures. The proposed SSCB consists of multiple parallel-connected silicon metal-oxide-semiconductor field-effect transistors (Si-MOSFETs), snubber capacitors and transient voltage suppression (TVS) diodes. A prototype is built and experimentally tested both at room temperature and in a liquid nitrogen (LN2) bath to validate the design. Experimental results show that the SSCB prototype, when immersed in LN2, achieves an on-state resistance as low as 68 μΩ at the rated current of 1700 A, delivering a high efficiency of 99.96%. Additionally, the SSCB successfully interrupted fault currents of up to 5360 A in LN2 of 77 K.