Anodic and cathodic erosion of Ag, Ag alloys and Ag-MeO contact materials in energy range below 10 joules

The main failures of switches and relays under DC low voltage in automobiles and telecommunications are contact material erosion and transfer. Also it is interesting for contact erosion prediction and reliability to evaluate erosion rates deduced from the ratio of mass loss to arc energy. In a previous work, we have reported that erosion and transfer could be reversed from anodic to cathodic mode when arc duration is enhanced by inductive load. Here we extend this work on erosion and discuss this inversion phenomena over a wide range of energy <10 J. So, specific devices are examined for speed separation control (1 mm/s-40 cm/s) load simulation (2.5-50 A, 0-4 mH), and arc duration control by parallel thyristor mounted on contact test. The fundamental result is that anodic erosion occurring at short durations and length becomes cathodic when arc length is extended to a critical value of /spl ap/100 /spl mu/m for AgSnO/sub 2/ and of /spl ap/500 /spl mu/m for AgCdO. At low energy and anodic length, erosion is enhanced in the following order of materials: AgSnO/sub 2/, AgNi, AgCu, AgCdO and Ag, but for long cathodic length this order is reversed. The effect of speed and inductance are examined and discussed in terms of arc length and energy. At low speed <3 cm/s, arc length is short, and it may produce large anodic erosion when it is supplied by high energy, as is is observed for AgCdO. Finally at inductance >.5 mH, dominating cathodic arc induces high cathodic erosion and erosion rate values are two times higher for AgSnO/sub 2/ than for AgCdO.