Dielectric strength of electric contacts after short‐duration arc in a hybrid DC circuit breaker

A hybrid direct current circuit breaker consisting of electrical contacts connected in parallel with a silicon carbide metal oxide semiconductor field‐effect transistor semiconductor device is capable of operating with low energy loss and high short‐circuit tolerance. It features a short‐duration arc discharge during current commutation; however, how the arc affects the dielectric strength between the contacts is not yet clear. This study conducts a quantitative evaluation of the dielectric strength after a short‐duration arc commutation. It is shown that the dielectric strength decreases after the arc commutation, and the breakdown electric field decreases as the arc duration increases. These results suggest that the existence of metal vapor and an increase in contact erosion caused by the commutation arc lower the dielectric strength of the electric contacts, in addition to the known effects of temperature rise of the contact surface and the air between contacts. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.