SECTION 3 - BRUSH THEORY AND CHARACTERISTICS
Question 3:10 What
Is Electrical Wear?
Electrical erosion is a major factor in how the brush will wear.
In addition to the particles breaking off and burning up, there is other erosion.
Just
as in electroplating, where particles are transferred from one surface to
another with current flow, this also occurs during brush current conduction and
erodes the brush and commutator away.
Fortunately current is also transferred by electron charging and this reduces the losses due to direct arc conduction. Arcing is an indication of direct electrical wear, therefore minimizing the arcing is important in reducing wear.
There is a tendency to transfer some copper from the surface of the commutator to the brush but these particles should normally vaporise or be expelled into the atmosphere. When there is excessive transfer of copper to the face of the brush the copper deposit often becomes work hardened and cuts into the commutator surface.
A variation of this
problem of excessive
copper
transfer is found in copper drag. The particles of copper are deposited on the
trailing edge of the commutator bars or brushes. For further information refer to Carbon Brush Face Analyser Chart.
Question 3:11 What Is Reasonable Brush Life?
The information has been drawn from experience of Morganite Taiwan Limited Application Specialists combined with a wide range of published information from major carbon supplier and motor manufacture. However, the material can not be downloaded, copied or used without written permission.
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