Arc-Free Bidirectional Hybrid DC Switch using Tungsten or Tungsten-clad Copper Contacts

A hybrid DC switch has been studied intensively because of the increasing demand for photovoltaic power stations and DC power distribution systems. The hybrid DC switch, consisting of mechanical contacts, semiconductor devices, and metal-oxide varistors, has the advantages of low contact resistance, high-speed current interruption, and a short-duration arc during current commutation. Moreover, arc-free current interruption is possible if the boiling voltage of the contact material exceeds the circuit voltage needed for turning on the semiconductor devices. A combination of tungsten contacts and SiC-MOSFETs satisfies this condition. As a result, an arc-free current interruption of 220 A was achieved with two-pole-tungsten contacts for bidirectional DC switching, where two SiC-MOSFETs were connected in series. The newly developed tungsten-clad copper contacts increased the threshold current of arc-free commutation up to 260 A.