Brush Distribution and Positioning

Carbon Brush Distribution and Positioning

DISTRIBUTION – It is clear that the precise adjustment of the neutral zone is essential for the correct operation of brushes and machine. But it is of the same importance that the brush holder distribution is geometrically correct around the commutator in accordance with the design of armature and windings. Always make sure that the brush holder arms are parallel to the segments of the commutator. The distance between brush holder and commutator should be 1.5 to 2 mm.

If the commutator has been machined, the brush holders will have to be reset to the correct distance.

POSITIONING – The grades of carbon brush to be applied to a particular machine have to be carefully evaluated as actual operating conditions can differ from those that the motor was originally designed for. This always represents a compromise. Due to variation of loads, commutator and carbon brushes are subject to a degree of abrasion over a period of time. When dealing with mechanical abrasion it would be recommendable to stagger the brushes in such a manner that every point on the commutator is brushed over to avoid tracks. Here, special attention is required to make sure that the brushes of a pair of poles run exactly behind each other. The brushes of the following pair have to be set slightly aside from the pairs running before and after it. Through this method the abrasion of the commutator can be evenly spread over the full width and as a result the formation of tracks can be avoided.

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Correct