Arc discharge process, arc root produces the thermal physical process due to concentrated energy release in the contact surface and near surface layer, caused by melting and evaporation of silver contact materials, this is silver contact electric ablation.
In the breaking current small and short arcing time under the condition of electric erosion mainly in material local micro evaporation source in the molten pool. With the extension of the current increases and the discharge time, in arc base ministry formation of molten metal in the weld pool, and strong evaporation and melting metal sputtering. In addition, the arc root tightening will cause the increase of the current density, the arc root temperature, resulting in increase of water evaporation and contact materials. The influence of temperature on the contact resistance is more complicated. As the temperature increases, the resistivity of the composite increased, but at the same time increased with the temperature of the micro surface deformation caused by the decline in mechanical strength and resistance will decline. In addition, due to the film surface layer usually has a semiconductor characteristics and membrane resistance will decrease with increasing temperature, but temperature can dramatically accelerate film layer in the atmosphere of growth process, so that the contact resistance increases, silver contact is easy to burn.
In the short-term electricity, on the contact surface temperature rises rapidly, on the other hand due to the beam in the vicinity of the current line bending, spontaneous breaking caused by contact of the electric force, causing short arc, two cases will lead to contact melting, the result is contact welding. When the current through the contact welding current is close to the critical value, the contact fusion welding happens to some extent. Silver contact material and contact surface directly affects the welding behavior. On the surface and thin layer heterogeneity can result in the enhancement of welding. Silver based contact materials with better performance by the electrical industry wide attention, but due to the influence of arc inevitably produced silver contact welding and arc erosion even expulsion and failure behavior, serious harm to the life of the electrical components.
How to avoid the failure will occur is an important aspect of the development of silver contact materials, many researchers from the add other elements such as rare earth elements of to improve its performance, and obtained some achievements, should be done in the future begins with the theory to improve the performance of silver based contact to electrical components.
Post time: Jul-07-2020