Make arc erosion and welding in the automotive area

A make are has been investigated using a new testing apparatus. This apparatus which includes a piezo-translator, enables controlled bouncing to be studied at make under mechanical conditions similar to those encountered in automotive relays. Material transfer and welding tendency of silver, silver alloys and silver metal oxide contact materials have been studied under inductive, resistive and lamp loads at 14 V de and 10-70 A. With all loads, anode to cathode material transfer has been observed. AgCdO, Ag and AgNi under lamp and resistive loads show the highest material transfer, as opposed to non doped and doped AgSnO2 under inductive loads. This well known transfer is due to the anodic are, which occurs during bounces when the gap between the contacts is shorter than similar to 5 mu m, at the beginning and the end of the bounce, We have demonstrated that welding occurs in the beginning of the bounce, i.e. when the contacts begin to separate under are, and not when the contacts close under are at the end of the bounce. It was found that welding occurs mainly with Ag, AgCdO, AgZnO, AgFeRe, and AgFeOx contact materials, and under high inrush current produced by lamp loads.