What is a Carbon Brush?

December 6, 2018

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Rotating machines are used for the conversion of mechanical energy into electrical energy or vice versa. All electrical machines whether motors or generators using direct or alternating current, depend for their actions on the principles of electromagnetic induction. Michael Faraday’s fundamental discovery, that a conductor whilst being moved through a magnetic field becomes the seat of electromotive forces (emf) and furthermore the direction of the electromotive forces is at right angles to both the direction of motion and the direction of magnetic field. The carbon brush is the integral part on the transfer of current in the rotating machine and although they differ in size, shape and technical composition carbon brushes and collectors all fulfil the same basic function. This is to transfer current from a moving device to a stationary point or vice versa within an electric circuit. The Carbon Brush is fitted in a brush holder which is designed to hold it in the correct position and allow the brush to run on the surface of the commutator or slip ring (collector) to transfer that currrent at optimum performance.

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Brush material grades

Electrographites - Commutation & Collection (Carbon partially transformed into graphite by heating to temperatures in the range 2200°C to 2800°C)

Biggest range of applications

• DC drives, & AC rings, etc.

• Current densities normally in the range 4 to 16Acm-2

• Surface speeds up to 50ms-1

Metal graphites - Mainly collection except for low voltage applications Copper -

• low voltage/collection of high current

• Current densities 12 to 30Acm-2

• Surface speeds up to 30ms-1 Silver -

• low voltage with good signal integrity

• Current densities vary from almost zero to 30Acm-2

• Surface speeds up to 30ms-1

Natural graphites - Collection

• TA exciters with steel sliprings

• Current densities up to 12Acm-2

• Surface speeds up to 80ms-1 Resin bonded - Commutation

• High contact drop (poor commutation) or low current/temperature applications • Current densities up to 8Acm-2

• Surface speeds up to 30ms-1

Metal impregnated - Commutation

• High strength/ high current requirements

• Current densities up to 30A/cm-2

• Surface speeds up to 40ms-1 Hard carbon & carbon graphites - Commutation

• ‘Older applications’ or Difficult commutation

• Current densities up to 10Acm-2

• Surface speeds up to 30ms-1

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Power Tool Carbon Brush & Holder


Carbon brushes are widely used in electric drills, angle grinder, hammer and other power tools . Because of the main material——carbon, carbon brushes are easily damaged, it need to be maintained and replaced regularly. Our carbon brushes are fine workmanship with good commutation ability, it also has long service life than normal carbon brush.


Our electrical carbon brushes are made from low friction conductive carbon materials including copper graphite, silver graphite, natural graphite, electro graphite, resin bonded carbon and pitch bonded carbon.


Contact JARCH today for the electric slip rings,hose reel,rotary joint,carbon brush your application needs. Contact us for CAD files and solid models.