Types of Carbon Brushes

A carbon brush is a component used to conduct electrical current between the stationary and rotating parts of a motor. In a generator or motor, the commutator rotates on a shaft and the fixed carbon brush rides on it to permit the flow of electricity and complete a circuit.

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

Carbon Brush Designs

Solid, one-piece carbon brushes: Solid brushes are the simplest type of brush used on the most basic of machines with little or no electrical and/or mechanical considerations.

Fractional HP brushes: These carbon brushes are also called "spring-loaded" because of the attached spring used to load the carbon in the brushholder.  Most of these applications are one piece, however, FHP brushes can also be split.  

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 brush allows for more electrical contact points between the brush surface and commutator and evenly distributed pressure or 'riding'capacity.  The carbons can be held together by a riveted clip, however, in most modern applications, they are glued to a rubber hard top.