Brushes for electrical machines

Brushes graphite - an external element of the sliding contact in electrical machines. The sliding contacts happen two types - ring and collector. Graphite serve in ring contacts of a brush only for a supply and withdrawal of current, and they at the same time serve in collector cars of a direct current for switching (straightening) of the variable electromotive force induced in an anchor winding. At normal switching of sparking under brushes it is not observed, and violation of switching results in premature wear of a collector and brushes graphite. However in many cases weak sparking is not reflected in wear of a collector and brushes that is provided by GOST 183 - 66 on electrical machines. To reduce or to absolutely liquidate sparking, it is necessary to reduce the arch current which is formed between a collector and a brush. Firm brushes from carbonaceous materials give the largest contact resistance.