Hi guys,

Thanks for the information!!
By the way,the brushes are not breaking in one position or one arm only.It is breaking randomly..If it is a raised bar, there will be a sequence of breakage,ryt?

Now i think about friction chatter..I will check the grade of the brushes they are using!!Thanks for the valuable information Acklin!!

By the way, i made a quick thermal report for the commutator..Itz attached here!!You can see the shunt wires coming out in R1-8 Motor...

Monitor man,
These are variable speed motors and the % of max load used, i have to check!!

Thanks again..

Have a nice day!!

Thermography_Report_of_R1-8___13_Motor_Commutator.PDF (169 Kb, 34 downloads) Thermal Report

Hi guys,

I got some pictures fo the broken brushes and the brush holders we are using!!

By the way, the motors are running at 48% of the load...

Have a nice day!!

This message has been edited. Last edited by: Jenish,

Hi guys,

This is one of the broken brush from R1-8!!

And this is the brush holder which we were using!!

R1-8 motor, are you sure of the temprature it seems extremly hot can it be verified by a contact termometer during shutdown. If motor run that hot it should trip.
Br
Monitor man

For what it is worth, I had a problem with excessive brush wear on a DC motor. I checked for all the usual suspects like raised segments, raised mica, spring pressure, brush grade etc. All of these appeared acceptable. I then tried an equivalent grade from a different brush manufacturer and the problem disappeared completely.

Two issues:

1) Your brush pictures look to be classic friction chatter – side polish and broken shunts. This will correlate to increased wear. Although the motor you mentioned looks to have angled brush holders (reaction) on their website, the commutator picture you posted looks to have radial brush holders installed (as mentioned previously, this is more common on European motors). Friction chatter is a result of an unstable leading (stubbing) brush holder arrangement. The angle must be in excess of 30°. If these are radial holders, a leading angle of 1° will be enough to cause the effect.
2) Your commutator appears to have no film or a very light film and there is some evidence of threading and grooving. Brush grades can be adjusted to accommodate for light loads or hostile environments so you might want to consult a local expert.

The comment by Paul N is a telling one – brushes made by different manufacturers will have different properties and will have different wear characteristics EVEN if quoted as equivalents. Additionally, different grades made by the same manufacturer will be purposefully different. Remember that OEM’s that manufacturer motors do not know where motors will end up and usually err on the side of a safe material as a brush grade – normal environment, normal load. If a motor ends up in a steel mill or a paper mill, GE or Reliance (now Baldor), will specify a specific grade suited to the application. Many other OEM’s are also doing this but too often, a standard mill motor with a standard grade may be applied. Usually, a motor OEM is supplying to a machine OEM who is supplying through some integrator or distributor – lots of voices and ears in the supply chain.

Supplying the most amount of information to the brush supplier can help in getting the correct grade for the application.

brushholder2.pdf (14 Kb, 15 downloads)