Gallium alloy as lubricant for high current density brushes

Experiments where gallium alloy is used to wet a slip ring in contact with current collectors are discussed. Alternating current (AC) density exceeded 1.5*10/sup 6/ A/m/sup 2/. Contact resistance variation with time is reported. Materials compatibility and wettability are discussed, along with observations on replenishment of the alloy film. Brushes were made in the forms of copper mesh pads and inclined copper fingers. Monolithic carbon brushes were operated on the same apparatus to provide a reference for comparison. Both forms of gallium-wetted brush were found to offer low resistance, low heating, and good tribological properties.>