The effect of rotating arc velocity on copper cathode erosion

Abstract

In a number of devices, transverse magnetic fields are used to rotate arcs to minimize electrode erosion. Measurements are reported here for 45 A arcs rotating in air at atmospheric pressure which show that the cathode loss, which exceeds that of the anode, can be determined with good accuracy if allowance is made for oxidation. These results, which have been made over a much wider range of arc velocity than any work reported previously, show that the variation of cathode erosion rate with arc velocity is not a simple one, and that an abrupt fall or increase can occur for a very small change in arc velocity, whereas it has commonly been assumed that increasing the magnetic field will continuously reduce the loss of electrode material. It is suggested that these considerable variations in cathode erosion are associated with changes in electron emission caused by differing oxide film conditions on the cathode surface.