DC GeneratorsDC GENERATOR THEORYFigure 4 Left-Hand Rule for GeneratorsCommutator ActionThe commutator converts the ACFigure 5 Commutator Segments and Brushesvoltage generated in the rotatingloop into a DC voltage. It alsoserves as a means of connectingthe brushes to the rotating loop.The purpose of the brushes is toconnect the generated voltage toan external circuit. In order to dothis, each brush must make contactwith one of the ends of the loop.Since the loop or armature rotates,a direct connection is impractical.Instead, the brushes are connectedto the ends of the loop through thecommutator.In a simple one-loop generator, the commutator is made up of two semicylindrical pieces of asmooth conducting material, usually copper, separated by an insulating material, as shown inFigure 5. Each half of the commutator segments is permanently attached to one end of therotating loop, and the commutator rotates with the loop. The brushes, usually made of carbon,rest against the commutator and slide along the commutator as it rotates. This is the means bywhich the brushes make contact with each end of the loop.Rev. 0 Page 7 ES-05
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