Abstract. As supply DC voltage levels in automobiles, aviation and aerospace are becoming higher, high voltage and large capacity compact DC electromagnetic relays or contactors are becoming more important. In this paper, experiments were conducted at DC 270V/100A in air and nitrogen, respectively, with CuCr40, CuCr45, CuCr50, CuW60, CuW70 and CuW90 as contact materials. Welding resistance (corresponding to electrical contact life), contact erosion and breaking arc durations were measured, and the obtained results were discussed.