Break arc duration and contact erosion in automotive application

Switches and relays connected to complex circuits (motor, resistance, and lamp) and supplied by 14 V dc imposed by the battery voltage are currently used in the automobile field. Arc duration and subsequent erosion measurements for contacts made of pure silver, silver alloys (AgNi, AgCu), and silver metal-oxides (AgCdO, AgSnO₂) were carried out. Also, the influence of the opening speed, current, and loads on this duration is determined. It was found that inductive load causes high voltage and gaseous arc phase development as was confirmed by spectra emission of surrounding gas N₂. So, arc duration is enhanced but keeps the same values for silver alloys as well as for silver metal oxides. Nevertheless, in resistive and lamp loads, the metal oxide materials show large arc duration compared to pure silver or silver alloys. Opening speed acts on arc duration differently for each load: it decreases as root square of opening speed in the inductive load whatever the current, but follows a linear decrease at high current in the resistive case. The lowest erosion and mass transfer observed in resistive and lamps loads are reversed and enlarged when the load becomes inductive. We report the remarkable minimum erosion of AgSnO₂ when loads are free from inductance. These results associated with measurements of erosion will be useful to choose contact material, electrical and mechanical conditions to improve lifetime and reliability of the components