Theoretical and experimental determination of erosion rate for silver contacts under 14 VDC

The erosion rate of electrical contacts is a fundamental parameter to understand and evaluate the performances of contact materials and their breaking devices such as the life time. In this study, we have focused our interest on the erosion in automobile applications under the 14 VDC power network. The experimental apparatus, adapted to perform contact breaking in similar conditions to the automotive relays, ensures arc duration control by artificial quenching, with a constant arc current close to 40 A. Erosion rates of the electrodes were determined by weighing before and after 5000 breaking operations.. In parallel, theoretical study based on a finite element calculation is conducted. A three-dimension simulation gives erosion volumes and liquid volume evolution versus time. To improve erosion resistance and avoid welding of the silver contacts at make, composites with additives, a one-dimension simulation was made to calculate erosion rate of such contact materials, except for AgSnO₂.