A fundamental experiment on operating characteristics of Ag, Pd and Cu contacts in inert atmosphere

The purpose of this work is to research the effects of the surrounding atmosphere of contacts on arc discharge and contact reliability in various aspects, and in future, to construct a systematic physical theory for various phenomena in gases, especially in inert gases. By filling the contact part with inert gas, prevention of increase in contact resistance is expected. This paper examines the operational performances of three typical contact materials, Ag, Pd and Cu, in a DC inductive (20 mH) load circuit with load current up to 3.0 A in air and in nitrogen gas. As a result, it is shown that in nitrogen atmosphere, contact resistance is lower and more stable and material wear and transfer is smaller than in air. Thus nitrogen gas has the effect of delaying and restraining deterioration of contact reliability. These consequences are considered to come from the difference of morphology and products on the contact surface, and moreover, the difference of arc duration and arc discharge phase