DC GENERATOR THEORYDC GeneratorsEach brush slides along one half of the commutator and then along the other half. The brushesare positioned on opposite sides of the commutator; they will pass from one commutator half tothe other at the instant the loop reaches the point of rotation, at which point the voltage that wasinduced reverses the polarity. Every time the ends of the loop reverse polarity, the brushesswitch from one commutator segment to the next. This means that one brush is always positivewith respect to another. The voltage between the brushes fluctuates in amplitude (size ormagnitude) between zero and some maximum value, but is always of the same polarity(Figure 6). In this manner, commutation is accomplished in a DC generator.Figure 6 Commutation in a DC GeneratorOne important point to note is that, as the brushes pass from one segment to the other, there isan instant when the brushes contact both segments at the same time. The induced voltage at thispoint is zero. If the induced voltage at this point were not zero, extremely high currents wouldbe produced due to the brushes shorting the ends of the loop together. The point at which thebrushes contact both commutator segments, when the induced voltage is zero, is called the"neutral plane."ES-05 Page 8 Rev. 0
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