What are electric motor brushes?

For an electric motor to work it needs electricity and one of the fundamental parts for this to happen are the brushes. To better understand how they work and the types, let's first answer the million dollar question: what are the brushes of an electric motor?

Beyond knowing what the brushes of an electric motor are, it is essential to understand how they work and how important they are. Carbon brushes are used to make the electrical connection between the rotor of an electric motor (the rotating part) and the fixed part.

The rings on the rotating shaft are generally made of copper and are connected to the rotating coil. The brushes are responsible for putting pressure on these, also called collectors, to allow electricity to pass through so that the motor can start.

Types of brushes

Now that we know what electric motor brushes are, it is important to mention their classification according to the type of material they are made of and their specific properties. Electric brushes can be divided into five main types:

• Amorphous carbon which are generally used for small motors with high revolutions.
• Electro graphite are mainly used in loading machinery or in direct current motors or alternating current motors with rings. In these, it is important to specify that they work perfectly with powers higher than 25 kilowatts, as well as intensities between 300 and 400 amperes.
• Bakelite brushes, made of bakelite, which are resistant to large amounts of current at start-up and can regulate the power of the motor itself.
• Flat brushes work best in applications that need a lot of conductivity, such as lightning rods, and in very small spaces.

Finally, metallo-graphitic brushes are ideal for a motor with very high currents and low voltages, which is why they are often used for forklifts or cranes.

When the starter motor has failures, it is very frequent that these occur due to the wear of the brushes, a matter that is fixed by replacing them. It is important to take into account that the brushes are in a context of permanent friction, so over time it is normal for them to wear out and not make good contact with the collectors.

Recently, brushless electric motors are being built, but this part is still present in household appliances, as well as in electric and industrial vehicles.

Contact our sales team who will be able to advise you on graphite raw material for the production of electric brushes.

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.