4 Things The Appearance Of The Commutator On Your DC Motor Can Tell You

28 July 2016
 Categories: , Blog

In order to get the most out of your DC motor, you need to pay attention to the warning signs that it gives you. Here are four different wear patterns that you may notice on your DC motor's commutator , and what exactly each of those patterns are telling you.

Normal Wear

When your commutator is wearing normally, the brushes that come into contact with your commutator transfer current to it. When this happens, some of the copper molecules on your commutator are vaporized. This results in a copper-oxide film being deposited onto the surface of your commutator. This residue will be very thin on the surface of your commutator and it will have a uniform color pattern that can range from a darker charcoal brown color all the way to a light tan color. You may also be able to see the path that the brushes make with your commutator very faintly. These are all signs that your commutator is working and wearing correctly.

Slot Bar Markings & Burning

Slot bar markings can occur naturally on your commutator and are not necessarily a sign that you need to do repairs. Slot bar markings are when there are both light and dark bars on your commutator. This happens naturally when either the last or first conductor goes under the brush when in operation.

Slot bar markings become concerning when they turn into burn markings. This can happen if an electrical overload occurs to your machine, or if the settings are wrong, or if your machine comes into contact with contaminants. When the slot bar markings start to look like they are etched into the surface, you need to resurface your commutator and correct whatever issue caused the burn marks in the first place. If you fail to correct the underlying issue, you will have to resurface your commutator again soon.


Another common pattern that you may see on your commutator is streaking. You'll see long, thick vertical lines, or streaks, on the surface of the communicator that may have a brown or black tint to them. There are a few different situations that can cause streaking on your commutator.

When contaminants come into contact with your commutator, such as hydrochloric acid, silicone vapors or other chemicals. If that is the case, you'll need to figure out where the contaminants are coming from and stop them from getting onto your commutator.

Another source of streaking occurs when metal is transferred from the commutator to the brushes. This can generally be fixed by changing the grade of brush that you use or by the tension setting of your brushes.


When there are numerous thin lines on your commutator, this is the result of lots of metal being transferred from your commutator onto the brushes. Like with streaking, this can often be fixed by changing the tension settings of the brush or changing the weight of the load.

Be sure to check the commutator on your DC motor every once in a while and pay attention to what the wear pattern you spot is telling you. Being proactive when you see the wear pattern change will help you extend the life of your DC motor. For more information, visit an auto store like Hardys Auto Parts LLC.