. The Bell System technical journal . tions of the square mating areas (about mm on aside) of heavj^ type U relay palladium contacts. The contact contoursare drawni to scale after the metal transfer resulting from repeated arcswith a total energy of 10^ ergs, using the values of Table II to convertthis energy into volumes of metal. The mounds and pits produced byinactive anode arcs and by inactive cathode arcs are assumed to bespherical segments, each having a height equal to half its radius. Thesmooth erosion resulting from active arcs would have depths which donot show up at all on the s
. The Bell System technical journal . tions of the square mating areas (about mm on aside) of heavj^ type U relay palladium contacts. The contact contoursare drawni to scale after the metal transfer resulting from repeated arcswith a total energy of 10^ ergs, using the values of Table II to convertthis energy into volumes of metal. The mounds and pits produced byinactive anode arcs and by inactive cathode arcs are assumed to bespherical segments, each having a height equal to half its radius. Thesmooth erosion resulting from active arcs would have depths which donot show up at all on the scale of this figure. For each electrode in eachof the four cases, the erosion is less than 2 per cent of the total volumeof the metal of the contact, and represents a fairly early stage in the ex-pected contact life. The electrode separations at which arcs occur corre-spond respectively to fields of 8 X 10^ 4 X 10^ and X 10^ striking voltage is assumed to be 50 and the separations are drawn SEPARATION SCALE CATHODE S. INACTIVEANODE ARCS ^ANODE CATHODES INACTIVECATHODE ARCS ; ANODE ACTIVEARCS Fig. 8 — Erosion produced by anode arcs at clean surfaces, bj^ inactive cathodearcs and by active arcs of either type, the total energy in each case being 10^ergs. The electrode separations at which these arcs strike correspond to 50 voltsand are represented here on a greatly expanded scale. 794 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1957 to a scale 200 times greater than the scale of the electrodes. For poten-tials that give air breakdown, the scale of separation would be changedby large factors. The sketches of Fig. 8 are of assistance in understanding some of thequalitative erosion differences observed in the four types of arcs (Ta-ble II). All of the metal lost from one of the electrodes in an inactive arcof either type comes from the surface of a pit, and from the figure itseems clear that all of it must obviously be intercepted by the otherelectrode because there is
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