ON-State Contact Resistance and Arc-Less Commutation Characteristics of Cu-W Clad Contact Materials in a Hybrid DC Switch

Hybrid dc switches have better performance with regard to energy conservation and less arc erosion than conventional semiconductor switches and mechanical switches. A novel hybrid dc switch based on a SiC-MOSFET is developed, and it accomplishes arc-less commutation if the current is below a threshold value, which is mainly determined by the boiling voltage of its contact material. However, as it is difficult for common contact materials to have both a low ON-state contact resistance and high boiling voltage, optimization of the contact materials is necessary to further decrease the ON-state contact resistance and improve the arc-less commutation characteristics of hybrid dc switches. New-type Cu-W clad contacts are proposed in this article by brazing tungsten top layers on copper bulks. The performance of the Cu-W clad contacts with the tungsten top layers of different thickness is evaluated by comparing their ON-state contact resistance and the threshold current of arc-less commutation with those of copper contacts and tungsten contacts under dc current ranging from 100 to 400 A. The results of the experiments show that the Cu-W clad contacts with the tungsten top layers of 1 mm thickness are the most suitable for arc-less hybrid dc switches because of their low ON-state contact resistance and largest threshold current of arc-less commutation.