Arc Termination Current on Breaking Contacts

Studies were made of the arc termination current on the breaking contacts with an inductive load. Test contacts were 2 mm cross rods of tungsten, gold, palladium, silver and platinum. The arc termination current was found to be closely related to an arc duration. The relation between the arc termination current and the arc duration was independent of the closed contact current (1-5A), the contact opening velocity (15-95 cm/s) and the slope of the arc current. When the arc duration was relatively short, the arc termination current increased linearly with the logarithm of the arc duration, and saturated at the specific value for each contact material. The saturation value was found to be nearly equal to the minimum arc current published by Holm. The arc termination current characteristics of silver-tungsten dissymmetric contacts were similar to those of the symmetric contacts of the cathode material.