# Motor Brush Replacement



## MikeFL (Apr 16, 2016)

cjoe said:


> I've always believed if we find a bad brush (chipped, short, broken lead...)during a DC motor PM we change all brushes but I've been questioned on this and haven't found a straight answer yet. We have guys who will replace one or two brushes out of 12 rather than replacing the set resulting in brushes of different length on the motor. If nothing else it prevents us from *knowing on future inspections if we have uneven brush wear* or just a poor maintenance method.


I think you just answered your own question. I do that all the time.

Another reason is that you're already in there. It would be penny foolish to let the next brush be the reason it gets taken off line and torn down. 

Welcome to the forum. :thumbsup:


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## John Valdes (May 17, 2007)

cjoe said:


> I've always believed if we find a bad brush (chipped, short, broken lead...)during a DC motor PM we change all brushes but I've been questioned on this and haven't found a straight answer yet. We have guys who will replace one or two brushes out of 12 rather than replacing the set resulting in brushes of different length on the motor. If nothing else it prevents us from knowing on future inspections if we have uneven brush wear or just a poor maintenance method.


I'm in the "change all" camp.
There are people that will disagree and I can get on board as long as each brush is exactly the same.
Brushes have specs as far as composition and physical attributes.
If for example you are using "National" brand brushes and know they are exact and interchangeable then I say replace as needed.
If you get all differing brands and composition then you need to be very careful.
I like to change them all at once then monitor the wear. The wear will tell you the story as well as the condition of the commutator.
Also by changing all at once you don't have to open the motor up so much. You can also make inspection covers from clear plastic material so you dont have to remove 6 bolts for each one. All you will need is a flashlight.
I know one company that installed low voltage lights inside the motor near the plexiglass covers so they could see inside. 

Do you "seat" your brushes or just install and run? Stay away from honing stones!


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## cjoe (Oct 2, 2010)

Mike and John thank you both for your replies. I appreciate your sharing that you believe that it is wiser to replace the brushes as a set and why you do. 

John - These are 200HP motors and we do seat new brushes. At least I'm hoping they guys who replace single brushes are at least seating the ones they replace. We do have Plexiglas covers so we can see arcing or other symptoms while the motor are running.

Thanks again for your help. I'm more comfortable addressing this issue and suggesting that it is worth the time and cost to do a better job of motor maintenance.


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## John Valdes (May 17, 2007)

cjoe said:


> Mike and John thank you both for your replies. I appreciate your sharing that you believe that it is wiser to replace the brushes as a set and why you do.
> 
> John - These are 200HP motors and we do seat new brushes. At least I'm hoping they guys who replace single brushes are at least seating the ones they replace. We do have Plexiglas covers so we can see arcing or other symptoms while the motor are running.
> 
> Thanks again for your help. I'm more comfortable addressing this issue and suggesting that it is worth the time and cost to do a better job of motor maintenance.


If you take that great attitude with you everywhere you go, you will go far! :thumbsup:
Glad to help in any way possible.


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