Comparison of Brush Contact Drop Characteristics with Copper Ring and Steel Ring, Considering Spark and Collector Ring Hazard

Brush and collector ring system is applied to rotating machines, such as large synchronous generator for thermal and hydraulic power plant and large AC synchronous and wound rotor induction motors for industrial applications. Recently as results of power electronics technology & microcomputer control technology, inverter fed AC adjustable speed large synchronous motor for steel rolling mill and variable speed water turbine generator with AC excitation wound rotor have been developed, realizing excellent performance. In these rotating machines, not only large current capacity but also high performance reliability is required to brush/collector system From these back ground, authors try to introduce new theory to brush/collector system, based upon more than one hundred years of brush/collector ring application histories and based upon some experiments by testing machine, which are introduced by field experiences of those machines.