What is a Carbon Brush for Electric Motors

What You Should Know about Motor Brushes

A carbon brush for an electric motor is an electrical contact which conducts current between the stationary and moving parts of the motor. These motor parts are seated in holders and are positioned above the rotation commutator or slip ring.  Carbon Brush applications include their use in electric motors and generators.
 

Why are they called "Brushes" for Electric Motors?

The term “carbon brush” appeared in electrical engineering history with the change to materials actually made from copper wire, which looked like a whisk brush, to graphite and carbon. Carbon brushes have been evolving for decades. Today, they remain indispensable hardware for DC electrical rotating machines.

What types of Carbon Brushes are used in electric motors?

Solid, one-piece carbon brushes: Solid brushes are the simplest type of brush used on the most basic of machines with little or no rotation considerations.
Split Carbon Brushes: Split bushes are designed by bringing together 2, 3, or more carbon sectors into one unit, resulting in optimal electrical and mechanical contact.
Splitting the carbon brush allows for more electrical contact points between the brush surface and commutator and evenly distributed pressure or 'riding'capacity. 
Fractional HP brushes: These carbon brushes are also called "spring-loaded" because of the attached spring used to load the carbon in the brush holder.  Most of these applications are smaller and one piece; however, FHP brushes can also be split.
 

What is Carbon Brush Commutation for Electric Motors?

Commutation (commutating current to complete the circuit) occurs when two or more carbon brushes contact the commutator. For further information on brush grades, see “Replacing Carbon Brushes for Electric Motors”.


Brush grades should be carefully chosen by considering atmospheric and running conditions, for the best commutation.
 

How do I choose which Carbon Brush is right for my application?

REPCO has published a Carbon Brush Catalog containing over 300 of the most popular replacement brushes. The catalog is arranged by motor manufacturer. Refer to motor nameplate or other source and look up your replacement in the Table of Contents.
Contact a REPCO carbon brush specialist for help in choosing the carbon brush type best suited for your application. Call 800.822.9190 or submit a contact request online. See our Carbon Brush, Electrical Contact & Coil catalog requests on the homepage.
 
Learn More:
How to Troubleshoot and Replace Carbon Brushes in an Electric Motors
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