Effects of Rotational Motion of Break Arcs on Arc Duration and Contact Erosion

An electrical rivet contact in which a column-shaped permanent magnet is embedded in the rivet shank beneath the contact head is mounted on a relay as the stationary contact. The moving contact is a conventional rivet without the magnet. The magnet forms radial magnetic field to rotate break arcs around the center axis of electrical contacts. A series of switching experiments are carried out in a 42VDC resistive circuit at currents of 7A, 10A and 14A. The contact material is Ag/SnO₂ 12wt%. Experimental results for break-only operations with the magnet are compared with those without the magnet. Effects of rotational motion of break arcs driven by the magnet are investigated for the contact erosion and arc duration. Without the magnet, the area of contact erosion on the contact surfaces is concentrated on the tip of contacts. With the magnet, on the other hand, the area of contact erosion is widespread on contact surfaces by the rotational motion of break arcs. The effect of the magnet is confirmed to result in a uniform contact erosion area. The arc duration is also shortened and found to be effective for larger circuit current.