Experiments on relationship between metallic phase and gaseous phase arc and contact resistance in ag contacts with opening arc

To investigate in detail the relationship between arc duration and contact performance (contact resistance and material wear and transfer) in Ag contacts, arc duration, and contact resistance were measured simultaneously at every contact operation. It has been known that contact resistance is low and stable if arcing continues only in the metallic phase and it is high if the phase is transferred from metallic to gaseous phase during arcing. To investigate the dependence of the arc duration‐contact resistance relationship on the phases, the relationship was evaluated experimentally with various transfer ratios under a constant electrical current of 2.5 to 3.5 A. As a result, it was found that the arc duration was related strongly to the contact resistance immediately after the arc. If the phase did not transfer to the gaseous phase, (he contact resistance was stable and was about 40 mω. Immediately after the transfer to gaseous phase began, the contact resistance increased by 3 to 40 mω. When the arc phase contained gaseous phase, the contact resistance increased by 3 to 10 mω at every operation and finally reached around 100 mω. Then, if arc occurred only in the metallic phase afterward, the contact resistance decreased by 3 to 10 mω at every operation and reached about 40 mω after 10 to 20 operations.