Effect of Permanent Magnets Embedded in Electrical Contacts Mounted on Electro-magnetic Relays

摘要

A permanent magnet is embedded in the center of an electrical contact mounted on a relay. The magnet is embedded to form radial magnetic field to rotate break arcs. An experimental circuit is resistive. The supply voltage is 42V. The circuit current when contacts are closed is 10A or 14A. Contact material is Ag/SnO_2 12wt%. Experimental results for break-only operations with the magnet are compared with those without the magnet. Following results are shown. Shortening effect of the arc duration with the magnet is more effective for higher circuit current. Break arcs are successfully rotated. Without the magnet the area of contact erosion on the contact surfaces is concentrated around the tip of contacts. With the magnet, on the other hand, the area of contact erosion is wide on contact surfaces by the rotational motion of break arcs. These results indicate that the effect of the magnet is confirmed to prevent the local contact erosion for break-only contacts.