The Effect of Impurities on the Contact Volage Drop and Copper Picking of Electrcal Carbon Brush

Abstract

An investigation of the effect of impurities on the contact voltaye drop and copper picking of electrical carbon brush is reported in this paper.Results obtained are as follows.(1) The contact voltage drop of negative brush (motor notation) is suddenly lowered as soon as water particles stick on the brush-copper slip ring contacts, while for the positive brush (motor notation) the effect of waterparticles is not observed.(2) The anomalous phenomenon of contact voltage drop for the negative brush is related intimately to the copper picking of brush.(3) If the surface of copper slip ring is covered with oxide films, the tendency of copper picking of negative brush is considerably diminished, although the contact voltage drop is lowered.(4) Various impurities, H20, CCl4, NaCl watersolution lower the contact voltage drop of negative brush and cause copper picking, and when the current density of brush is zero, these phenomena are not observed. While the other impurities, benzene, and benzine, cause no change in the contact voltage drop and the contact surface of brush. It is concluded that the anomalous phenomena of the conact voltagedrop and copper picking of brush with impurities are due to the electrolytic phenomena.