Electric contact materials and their erosion in automotive DC relays

Compares the contact resistance, welding, and erosion of three basic contact materials suitable in automotive DC relays for 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 were a silver alloy (98Ag-2Cu), a metal-oxide composite (Ag-SnO/sub 2/ with WO/sub 3/ additive), and 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 results were explained in terms of the arc erosion process and inherent material structures. All three types of contact material have their pros and cons in automotive applications.<>