Load Commutation Switch for a Hybrid DC Circuit Breaker in Cryogenic Environment

Electric aircraft could significantly reduce carbon dioxide emission and achieve ecological and sustainable development objectives. Cryogenic and superconducting technologies have the potential to boost the development of electrical propulsion aircraft. However, the low impedance of DC networks could result in extremely fast rising DC fault current, which poses a substantial challenge for DC fault protection. Furthermore, the design of components capable of operating at cryogenic temperatures is another challenging task. This paper, for the first time, presents the design and experimental performance of a load communication switch (LCS) as key integral part of a high-current hybrid DC circuit breaker at cryogenic temperatures. A low-voltage silicon metal-oxide-semiconductor field-effect transistor (Si-MOSFET)-based load commutation switch has been built and experimentally tested in both room temperature and liquid nitrogen (LN2) bath. The experimental results show that the on-state resistance of LCS submerged in liquid nitrogen bath is as low as 23 μΩ, comparable with contact resistance of mechanical switches. Correspondingly, the conduction loss of the prototype LCS in LN2 is as low as 64 W at 1700 A, which is only 23% of power loss at room temperature. Meanwhile, the fast current commutation driven by the LCS from the mechanical switch to the main breaker during the fault current interruption has been successfully verified.