What Does A Brush Holder Do And How Does It Work?

By Author: Stevan Gerrand
Total Articles: 53
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Carbon brush holders are an essential part of electric motors, although many people don't understand what they do or how they work. Carbon brushes are typically found inside of electric motors that use DC, AC, or a combination of both types of power. The brushes actually conduct electricity from moving part to moving part, so if they are malfunctioning, the electric motor won't work.

The Responsibilities of a Brush Holder

The brush holder is, as the name suggests, the piece that holds the brush. However, it does much more than simply hold the brush as the machine operates. The brush holder is responsible for ensuring that the brush itself works properly and delivers current precisely where it needs to go. The holder actually provides support for the brush, holding it in just the right position that it needs to be in so that it can make contact with the surface of the electrical conductor. If the contact is not made exactly right, then the entire motor won't work properly.

In addition to the holder being able to hold the brush in the right position so that electricity is conducted from moving part to moving ...
... part, the holder also must be attached with just the right amount of tension. It must be held in a constant position that never moves, and big problems can develop if the holder is attached too tightly or too loosely. If the brush holder isn't attached just tightly enough and held in the perfect position, then the brushes that are inside the holder will wear out much more quickly than they would otherwise.

Understanding How Brush Holders Work

You will find the holder around the commutator inside the electric motor or around the top surface of the slip ring in machines that have slip rings. Inside electric motors, there are typically moving parts that are rotating. The brush must be in contact with the rotating shaft in order for the motor to work. If the holder provides pressure that is inconsistent or uneven, temperatures could rise inside the motor and it could end up overheating. Corrosion can also occur, causing even more problems for the motor.

One important component of the holder is the spring, which helps push the brushes up to the rotating commutator. As the brush wears down, the spring continues lifting it up from the base of the holder, thus keeping the pressure consistent even as the brush wears down over time.

Often a single holder is part of a larger assembly of brush holders, which are usually mounted in parallel fashion across a large commutator. This type of setup is commonly found in very large electric motors. It is needed when a lot of power (more than a single brush can handle) is required to run the motor. The brush assembly then distributes the power evenly across all of the brushes in the assembly, thus enabling the conduction of a lot of electricity.

Maintenance on Brush Holders

In most cases, doing maintenance on the holders is fairly simple. Today's modern technology has made them fairly easy to simply slide the spent brushes out and insert the new one into the holder.

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