Arcing and its subsequent degradations on the contact material of automotive power relays and switches: welding

摘要

Our study aims to investigate the degradations of the contact material under arcing, in automotive power relays and switches. Our previous article dealt with the problem of material transfer between the contacts. In this article we will present our results on the problem of welding of the contacts under arcing. We used a testing apparatus to simulate the make switching. Tests were carried out with lamps loads, at the voltage of 14 V DC, and the inrush current at make was from 20 A to 180 A. At first we investigated the welding process. We showed that welding occurs when the contacts open under arc, at the beginning of the bounce, and only with lamps load. At the opposite to other applications, welding does not occur when the contacts close under arc, but when the contacts open under arc. This welding phenomena at break occurs because of a high material transfer under a short contact gap. Secondly we investigated the performance of various material (Ag, AgNi, AgCdO, non doped and doped AgSnO{sub}2, AgZnO, AgFeOx...). We measured the welding forces and the welding tendency. Doped and non-doped AgSnO{sub}2, was found to be the best materials.