SECTION 3 - BRUSH THEORY AND CHARACTERISTICS
Question 3:11 What Is Reasonable Brush Life?
Brush wear cannot be predicted in absolute values because so many conditions affect brush performance.
The life of the brush is not the absolute criteria and is often over emphasised. Commutalor wear and poor condition is generally more costly than expendable brushes. If the Commutator is in good condition, provided that the wear rate and carbon deposits are not causing excessive maintenance or other problems, it is often better to leave things as they are.
2-7mm per 1000 hours for stationary machines are considered reasonable.
This means for a brush with 25mm of available wear the life is 3,500-12500 hours.
To put this into perspective a machine with a commutator diameter of 300mm operating at 1500 RPM for 24 hours a day duty (approximately 8000 hours running) will result in the brush being dragged over the commutator surface the equivalent of 680000 km or approximately 16 times around the world each year.
While it may sound odd there can occasionally be a problem of too little brush wear. Some carbon particles are needed for formation of the patina. Brushes which are excessively hard for a particular application may cause glazing of the commutator and brush face and lead to brush chatter and deterioration of the patina due to improper film forming.
Question 3:12 What
Cause The Commutator Or Slipring Patina?
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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