PLASMA-SPRAYED CONTACT MATERIALS FOR VACUUM INTERRUPTERS

Contact materials fabricated by normal powder metallurgy and by plasma spray techniques [1] are investigated for their arcing properties in commercial vacuum circuit breakers. Current chopping levels tested up to 100 000 operations are found to be of the same magnitude. The high current interrupting capability is found to be comparable. The dielect ric strength of the plasma sprayed materials is negatively affected by the process as spontaneous breakdowns occur more frequently. Neverthe less, the potential of the plasma spray process is immense as it allow s easily to cover different contact surfaces and shields the contact w ith thin sheets of contact material, thus allowing for minimizing the skin effect.