Some characteristics of switching contacts riveted on the tips of both supporting arms arranged partially in parallel

Abstract

To a relay with supporting arms in which only the tips with electrical contacts are parallel, AgCdO electrical contacts with Au flash are installed as a normally open contact pair. Within the circuit with dc 30 V ‐ 10 A and a resistive load, it is used as the make‐only, the break‐only, and the make‐and‐break contact pair. the electrical characteristics at each make and break and the contact surface damage after 100 thousand operations were measured. In the sample electrical contact pair with the tips of supporting arms in parallel, it is demonstrated by experiments that arc damages (roughness and black and brown contaminant) occur at the center of the contact surface. The arc trace at the make‐only electrical contact is the narrowest in comparison with two other switching operations and is a milky metallic color surface with many infinitesimal irregularities. In the case of the break‐only and make‐and‐break contacts, large irregularities exist at the center of one of the electrode surfaces. A thick black and brown contaminant exists in this part and surroundings. Also, contact sticking occurred in all samples of make‐only contacts but not in the break‐only contacts. The black and brown contaminant between the contact surfaces prevents locking and increases the contact resistance and the variation width so that they cause a longer duration in the breaking arc.