New Configuration of Contacts for Increasing the Threshold Current of Arc-Free Commutation in a DC Hybrid Switch

Hybrid dc switches (HDCSs) have attracted considerable attention due to the low ON-state loss and fast current interruption. With low current interruption, there is no arc generation between the contacts. However, arc discharge occurs between the contacts after the contact opens for a high circuit current. Arc discharge is a harmful phenomenon. It erodes the surface of the contacts and decreases the insulation strength between the contacts. This article presents a new configuration of contacts that can increase the threshold current for arc-free commutation. The contact has a cuboid shape with a join of copper and carbon. When the contacts are in the closing position, the copper and carbon materials of the contacts come in contact. Then, a low contact resistance can be achieved. When the contacts start opening, the contact spots of the copper start decreasing until rupture, but carbon, which has a higher resistivity than copper, still remains in contact. With a higher resistance of the contacts, the current is further commutated to the semiconductor device until the current at the contacts becomes low. After the contacts rupture, the low surge voltage from the inductance in the circuit cannot ignite arc discharge. Thus, arc-free commutation can be achieved.