Study on molten bridge behaviors with arc-less current commutation in a hybrid DC circuit breaker

Hybrid DC circuit breaker (HDCCB), which combines a mechanical switch and a semiconductor, has become a research focus due to a rapid development of DC power system and its low on-state loss and short break time. However, there is still serious arc erosion for a conventional HDCCB because the current commutation is driven by the arc. A novel topology of HDCCB was proposed in former research. It is established based on a SiC-MOSFET which enables it possible to commutate current just in the molten-bridge stage. Thus an arc-less commutation is achieved. In this paper, firstly the influence of commutation on molten bridge is studied by comparing the molten bridge behaviors with and without current commutation when load is 60 V/150 A. And then, it is investigated how current value, separation speed and contact materials affect molten bridge performances in commutation condition. The experiments are carried out by using Cu and W contacts in open air when current is increased from 50 A to 200 A and the separation speed ranges from 0.04 m/s to 0.16 m/s. The results of this paper are meaningful for the optimization of this arc-less commutation hybrid DCCB.