High-Current Brushes, Part V: Subdivided Monolithic Brushes at Very High-Current Levels

Effect of polarity and various contact pairing combinations of electrographite, polymer-bonded graphite and copper on the performance of sliding electrical contacts

“…In addition, some other studies, although not focusing and analysing the wear of contact surfaces, report the effect of polarity on the contact resistance or the coefficient of friction. Many earlier studies observed a higher contact resistance under a positive graphite brush than a negative brush [19,20,22,24], although the opposite effect was also detected [21]. While in graphite/copper contacts the positive graphite brush (or disc) is in contact with a negative copper brush (or disc) and vice versa, this means that the electrical sliding contact where the current direction is from copper (positive) to graphite (negative) wear much more than the opposite contact (current flow from graphite to copper disc).…”

“…Many studies [1, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] have reported that polarity (the effect of the current-flow direction) has a significant influence on the friction, the contact resistance or the wear of contact surfaces. However, not many studies have looked at this effect in depth.…”