Do you know what motor brushes are? Find out here!

Motor carbons or brushes are the electrical connection between the fixed and rotating parts of an electric motor or generator. That is to say, it joins the fixed part with the rotor coils.

To do this, graphite blocks are used to press on the collectors on the rotating shaft by means of springs to establish the electrical contact. Recall that graphite, an allotropic form of carbon, is an excellent conductor of electricity.

These graphite brushes are widely used in motors in industries such as glass, transportation, steel, cement, mining, textiles, etc. It is just because of its electrical conductivity and chemical resistance that it is also used to manufacture electrodes.

Brushes are usually made of different types of carbon to suit the needs of the motor. There are amorphous carbon brushes for high revolutions, but in small motors, for example, in electro portable machines.

Likewise, there are motor brushes made of electro-graphite, especially for loading machinery, or of metal with graphite for cranes that have a motor operating at low voltages and very high intensities.

There are also bakelite brushes (graphite with bakelite) that withstand high current intensities in the starting phase and are capable of regulating the motor power. Finally, there are flat brushes for dynamos, for example. In other words, applications in small spaces and where high conductivity is required.

Types of motor carbons

There are different types of carbons for direct current and electric motors which, if we classify them according to their operation and applications are:

• Wired These are carbons that have between one and four wires that conduct electricity to the brush.
• These have a spring and are used for small tools, small motors, as well as fractional.
• Rivetted: Whether rivet with one wire, rivet with two wires, bi-parted with one wire or bi-parted with two wires, riveted carbons, as the name implies, have a rivet front and back and a wire.
• These carbons have two or more carbon pickups and at least one wire per pickup.
• Dumbbell: At each end of the wire there is a carbon.
• For lathe: Also called spark plug type and are specific for conventional lathes.
• Contact type: These carbons do not have wires and are commonly used in scissor slide bearing slip rings.
• These consist of a spring, a carbon holder and the carbon itself.

However, carbons are not only used for brushes, they are also present in abrasives, clamps, drill bits, welding machines, concrete bits and other components of power tools and motors in general.

Limitations to consider

Performance depends on graphite grade, grain orientation, temperature, load, pressure, speed, and operating environment. Material selection should be confirmed for your actual process conditions.

Information needed for a quote

To guide selection or prepare a quote, ESGRAF typically needs:

• Application and operating conditions (temperature, atmosphere, load).
• Dimensions, technical drawing, or CAD file when applicable.
• Required quantity.
• Requested grade or material currently in use.
• Observed issue with the previous part or lubricant, if any.

Request a quote

Share these details with our team at ESGRAF or request information. A specialist will review your application before recommending a grade or geometry.