SECTION 1 -INTRODUCTION TO BRUSHES AND CARBON GRADES
Question 1:8 Are Slipring And Commutator Brushes Different?
While some grades of carbon can be used in either applications there are differences in their function.
Slipring brushes have only to conduct the required current to a solid ring and generally have the wider dimension at right angles or tangential to the shaft with the appropriate number of brushes per ring base on the size and grade of carbon necessary to carry the required current.
Low resistance electrographite brushes are used for lower currents and copper graphite having percentages up to 90% copper or more are used for higher currents. Brushes with 50%-75% copper content are the most common brushes encountered on sliprings of wound rotor motors.
The construction of a slip ring brush will usually be of a solid construction with the lead number and size to carry the relatively high currents usually involved.
Commutator brushes generally have their widest dimension axially along the length of the commutator segments with the number of brushes per arm according to the required current and type of carbon used.
Commutator brushes can be of the copper graphite type for less than 48 volt DC supply because of the high current involved. However, by far the bulk of commutator brushes will be of the electrographite type with medium to high resistance depending on the load and machine design.
The construction of commutator brushes can be varied from a solid brush to the most complex multi-wafer type with grades and other features from a large range of possibilities.
Question 1:9 Are There Any General Principles For Grade Selection?
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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