1965 年 1965 巻 41 号 p. 3-10
Main traction motors MT 200 for the New Tokaido Line, which are used at high speed and high current density in pulslating or direct current, are carefully designed in order to keep good commutation and the brushes used are split ones made from soot. As tempered colour was considerably noticed at the pig tails of brushes in the car running test, unbalanced current among brushes was measured in the original machine with the voltage drop method at stand test of factories.
Obtained results are followed;
(1) Unbalanced current between brush splits is higher at the leading split than at the trailing one, and indicates considerably larger value than the general unbalanced current among parallel brushes. This causes are assumed mainly to be the motor design constructed of over-commutation.
(2) Though sliding charactristics of split brushes depend upon each split moving independently, this independency causes unbalnced current.
(3) Since the unbalanced current in split brushes is unavoidable, selection of brush current density and fastening method of brush pig tails should be designed move carefully.