Performance of Snubber Capacitors and TVS Diodes for Cryogenic Power Electronics

Power electronics plays a major role in energy conversion systems from motor drives to energy management and protections. The cryogenic and superconducting technologies have the potential to improve the power density and efficiency, in particular for future hydrogen-powered electric aircraft. However, commercial components in power electronics converters are not designed for cryogenic temperatures. To enable power electronics for applications such as superconducting propulsion system, it is essential to investigate their performances at cryogenic temperatures. In this work, several commercial polypropylene metallized film capacitors for snubber applications were experimentally evaluated in liquid nitrogen bath and room temperatures. The results show that the mismatch of coefficient of thermal expansion for packaging materials and technique leads to physical damages of film capacitors after thermal cycling from room temperature to cryogenic conditions. In general, polypropylene film capacitors exhibit a slight increase in capacitance and excellent stability in dissipation factor and voltage withstand capability in liquid nitrogen. Meanwhile, a commercial transient voltage suppression (TVS) diode was also investigated for cryogenic conditions. The breakdown voltage of TVS diode is found to be reduced by approximately 14% in liquid nitrogen compared to that at room temperature.