Development of an arcless DC circuit break using a mechanical contact and a semiconductor device

Abstract

Direct current circuit breakers (DCCBs) have receive considerable attention due to their increasing demand in DC power transmission and distributed generation. A hybrid DCCB comprising a mechanical contact, semiconductor device (SiC- MOSFET), and metal oxide varistor offers a small contact resistance when the mechanical contact is closed. After opening the mechanical contact, the contact voltage increases because a molten metal -bridge is formed between the contacts as a result of joule heating. This molten-bridge voltage promotes the current commutation from the mechanical contact to the SiC-MOSFET. After the current commutation is completed, a fast current interruption can be achieved by turning off the SiC-MOSFET. Therefore, the hybrid DCCB can achieve both a small contact resistance and a fast current interruption. In our previous papers, an arcless commutation was reported at the initial stage of the hybrid DCCB opening under a special condition. In this report, higher molten-bridge voltage was obtained using 2-pole contacts connected in series and using high-boiling metals. The higher molten-bridge voltage enabled the hybrid DCCB to interrupt larger current without any arc discharge. Finally, we performed DC current (300 V-150 A) interruption experiment, and succeeded in obtaining arcless current interruption with a probability of 100%.