The Role of Carbonaceous Particles in Low Current Arc Duration Enhancment. II. Arcs Occurring on Approach of Electrodes

Part per million concentrations of some organic vapors in telephone relay environments are known to produce carbonaceous particles on arcing contact surfaces. Enhanced arcing then occurs and the reliability and contact lifetime of the relays is impaired. The enhancement of break arcs due to the presence of carbonaceous particles has been described in paper I. Break Arcs.6 In this present paper the enhancement of arcs occurring on approach of electrodes (make arcs) is discussed and is thought to be due to the injection of plasmas formed by the electronic and ionic bombardment of carbon particles on the anode and cathode respectively. The plasmas formed from these particles can then be related to arc-duration enhancement. The observation that under `activated´ conditions no anode-type arcs exist but those that form are all of the cathode variety, can also be explained by the model. A calculation of the amount of carbon required to fully activate a 10-2 cm2 contact area yields 6.3 × 10-8 gm in agreement with values of other workers.