Abstract
Abstract The major factors which determine the voltage drop inequality under heteropolar metal-containing brushes operated with copper collectors or slip rings were studied. It was shown that polar effects are connected with the transfer of part of the electric current through transferred brush material on the collector surface and with the semiconductor properties of the collector film developed under such conditions. The relation between the contact voltage drop for the anode-polarized ( ΔU + ) and cathode-polarized ( ΔU − ) brushes is determined by the type of the collector film formed. With intact cuprous oxide layers beneath the transferred material layer, the relationship ΔU − > ΔU + is satisfied; with destroyed cuprous oxide layers the relationship has the opposite sign. For the range of electric loads found in electric machines, the metal-containing brushes form collector films with “gaps” within the protoxide layers beneath the transferred layer, which explains the observed inequality ΔU + > ΔU − . With the brushes operated along individual paths on slip rings, an increase in the brush material in the collector film under the anode-polarized brush, and a decrease under the cathode-polarized brush, contributes to the occurrence of the inequality ΔU + > ΔU − . An equivalent model of the brush contact is suggested to account for the peculiarity of the current flow under heteropolar brushes.
Published Version
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