Electric contact materials and their erosion in automotive DC relays

Proper contact material selection is critical for reliable performance of automotive relays. Three types of contact material were compared in a 20-A relay, which were switching lamp, motor, and resistor loads. The three contact materials chosen have different material strengthening mechanisms so that their effects on the arc erosion process could be evaluated. They include: (a) a silver alloy (98Ag-2Cu), (b) a metal-oxide composite (Ag-SnO/sub 2/ with WO/sub 3/ additive), and (c) a metal-metal composite (Ag-20Ni). Contact resistance, welding, and DC transfer characteristics were compared in make-only, break-only, and normal make-and-break switching operations. The observed results were explained in terms of the arc erosion process and inherent material structures. All three types of contact material have their own pros and cons in automotive applications.<
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