The electrical erosion of high tungsten content, tungsten-copper(7-10 wt.% Cu) was investigated. The contacts were placed in a vacuuminterrupter envelope with a background pressure of about 10-6torr. The contacts switched one half cycle of 60 Hz current peroperation. The polarity of the current was changed on each operation.Six contact pairs were investigated. Each pair was subjected to anever-increasing number of operations: 1K, 5K, 10K, 20K, 40K, 50K and60K. The contact erosion was inferred by measuring the linear positionof the moving contact terminal. On completing the electrical testing,the vacuum interrupters were dismantled and the contact surfaces wereobserved. Unlike the previous work on Ag-WC (50 wt.% Ag) and Cr-Cu (75wt.% Cu), the W-Cu contacts showed a localized build up of erosionproducts on the contact surfaces, even beginning at 1K operations. Theexperiments involved repeated switching of a unidirectional current,i.e. the contacts remained at the same polarity throughout theexperiments. Here, an anode pip and a cathode crater were formedimmediately. The different topographies of these contacts are discussedin terms of the metallographic analysis of the deposits on the contacts,the erosion deposits on the shields surrounding the contacts and theexpansion of the vacuum arc
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