Carbon brush is the sliding contact part of conduction current from Stationary part to rotating part in motor or generator,it can make no spark when DC motor commutation.

1)One or more pieces of carbon block 

2)One or more wire /terminal

We need to consider these parameters form 3 parts:

-Slip ring and commutator surface quality (Roughness)

-Coefficient of friction(“μ”)

-Vibration

-Correct pressure on carbon brush Slip ring or commutator

-Brush holder

-Voltage drop

-Commutation(DC motor)

-Current density

-Resistivity

-Humidity

-Corrosive vapor or gas

-Oil pollution and hydrocarbon

-Dust

-Do not mix different grade carbon brush on one motor, to avoid malfunction.

-The existing oxide film must be removed when change different carbon brush grade

-Make sure carbon brush can slid freely in brush holder,no too much gab.

-Make sure carbon brush with correct direction in brush holder,and pay more attention to carbon brush with bevel top,and sandwich type carbon brush with metal pad on top.

-Use carbon brush pre-grinding millstone to pre-grinding when low speed or no load,to make the radian of carbon brush contact surface and slip ring or commutator accurate anastomosis. Millstone’s dust can make the contact surface with correct radian in short time.

Its necessary to grinding again by medium particles millstone after pre grinding.

After whole pre-grinding process,you need to clear the contact surface thoroughly

-Confirm brush holder in working position,and check out brush holder surface inside.

-Adjust distance to 2.5-3.0mm between brush holder and commutator

-Check out spring pressure by pressure gauge,make sure spring pressure on each carbon brush is average.

-Confirm circle beating no more than 3mils,no visible defect on surface.

-Clean surface by medium particles millstone, sandpaper and emery cloth is prohibited.Keep suitable roughness(1.3-2.8μm),to produce and maintain good oxide film.

-make sure all carbon brushes slid freely in brush holder,wires contact correctly,terminal is tighten.

-then start motor from low load, increase load slowly,untill to full load.