A study on brush wear under commutation arcs in gasoline

The dc motor for an automotive fuel pump has a distinctive feature in that its commutation is carried out in a gasoline environment. The study of brush wear under commutation is generally important from the point of view of its reliability and durability. In this paper, the wear of the copper-graphite brush sliding against the copper commutator under commutation arcs in gasoline and air is reported. It was made clear that the brush wear in gasoline was more severe than that in air on both polarities when the commutation current was set to 10 A including arcs. In order to make the influence of arcs clear on the brush wear, we also examined the brush wear with load current but no arcing and the material transfer in switching contacts with arcing, which gave us the information of electrical erosion. In addition, we analyzed worn brush surfaces after these tests with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). As a result, the arc has a serious influence on the brush wear in both environments, but how to erode the brush surface by arcing in gasoline is different from that in air.