Observations of Extreme Cases of Contact Activation

The process of contact activation or arc duration enhancement has been observed between various precious and nonprecious metals in highly activated (2 X 10^-3- 100 torr) organic vapor-air mixtures. The results suggest that the enhanced arc durations observed under field, and some laboratory conditions, may only be an early stage of contact activation. A condition of extreme activation occurs where the duration of the enhanced arcing may be considerably reduced, and the voltage-time curves of contact opening show an almost continuous transition from zero potential to the open circuit voltage. At this stage the contacts are observed to have large amounts of carbonaceous particles present on them. This phenomenon of arc duration reduction under extreme activating conditions has been tentatively explained by considering a carbon particle bridging process between the electrodes.