Influence of the pulsating current amplitude on the dynamic friction coefficient of electrographite brushes Original Research Article

The friction coefficient occurring at the brush sliding over the collector segments is of great importance in the choice of the optimum brush for a specific commutating machine. Therefore special attention is given to this brush paramater, both in determining its value (due to losses and heating of the commutation assembly) and in the explanation of the changes occurring in the brush-collector contact zone. Unlike the well-known research in which the static friction coefficient of a brush is determined indirectly by measuring tangential forces acting upon the brush, in this paper the influence of the pulsating current amplitude on the static and dynamic friction coefficient of an electrographite brush is obtained using the “electrical balance” method. The experimental analysis has shown that an increase in the pulsation current amplitude leads to a decrease in the brush-collector friction coefficient resulting in the decrease of mechanical losses at the collector and a change of electrical losses.