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Am I Wrong Cleaning Silver Braised Contactor Pads with a Wire Wheel

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I have been working with MV, 600v motor starters and trying to get them in better operating condition. One thing I tried was to clean the contact pads on a wire wheel. I noticed immediately following cleaning visible arc flash from the contactor cover holes(See link, 6 small holes). Operation is otherwise normal and efficient. Is this normal/safe? I see this as acceptable in there is a small point where the high volts and clean pads would arc the atmosphere gap, before physical contact from engagement. However, I want to ensure that I am not making a mistake. The contact pads appear to be solid silver braised onto copper arms. In this case I would consider continuing this regularly as Preventative Maintenance. However, I want to know for sure.

Am I safe in what I am doing and should I continue to do it for restoring these starters? Or am I building a “bomb” that will later become a bigger issue? What are your thoughts, concerns, advice?
Thank you.

The specific starters are Eaton A200M2CAC Model J. I have included some photos of the contact feet.

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I have been working with MV, 600v motor starters and trying to get them in better operating condition. One thing I tried was to clean the contact pads on a wire wheel. I noticed immediately following cleaning visible arc flash from the contactor cover holes(See link, 6 small holes). Operation is otherwise normal and efficient. Is this normal/safe? I see this as acceptable in there is a small point where the high volts and clean pads would arc the atmosphere gap, before physical contact from engagement. However, I want to ensure that I am not making a mistake. The contact pads appear to be solid silver braised onto copper arms. In this case I would consider continuing this regularly as Preventative Maintenance. However, I want to know for sure.

Am I safe in what I am doing and should I continue to do it for restoring these starters? Or am I building a “bomb” that will later become a bigger issue? What are your thoughts, concerns, advice?
Thank you.

The specific starters are Eaton A200M2CAC Model J. I have included some photos of the contact feet.
wire wheel is the wrong tool, it will make the surface to rough
 

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Ready-Mix Electrician
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Those look like contacts out of a Furnas starter. The normal operating surface of contacts is “rough”. In operation, the hill and valleys interlock for an even greater amount of surface area.
My inspection is remove the arc cover and check for major wear or burning, and if none observed, reinstall the cover. No “dressing up” is done. I’m even reluctant to remove and reinstall used contacts because at least in my mind the relationship has now been shifted and the hill and valley interlocking is now off and will have to reseat itself at the cost of heat and wear.
 

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Discussion Starter · #9 ·
Those look like contacts out of a Furnas starter. The normal operating surface of contacts is “rough”. In operation, the hill and valleys interlock for an even greater amount of surface area.
My inspection is remove the arc cover and check for major wear or burning, and if none observed, reinstall the cover. No “dressing up” is done. I’m even reluctant to remove and reinstall used contacts because at least in my mind the relationship has now been shifted and the hill and valley interlocking is now off and will have to reseat itself at the cost of heat and wear.
They are 600v motor starters. Old, but they are pretty reliable of a build. I am just hoping to surf that 80's era build of solid silver contacts.
I know I asked and am greatful for all input rendered forth. I would hate to then question. But I find myself confused on a few points.

- Why would you want the contact surfaces to be rough? Greater continuity would be achieved by a firmly seated, smooth/clean surface of conductive material. In which case, I would argue the positional alignment wouldn't hold as much bearing on continuity as a clean, smooth surface with proper pressure would. As the contactors, by design, will "reseat" the topical engagement evertime the coil energizes. In addition, as my experience has proven (with signals at least) regular "reseating" of continuity ensures good electrical "communication".
Perphaps I am missunderstanding your words?

- Wouldn't the accumulated residual, more specifically in dirty environments, cause increased heat/wear on the dynamically contacting, high voltage contacts anyway?

Again, this is not in arrogance but learning.
Thank you.
 

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Discussion Starter · #10 ·
It is my understanding that the surfaces are plated with something that reduces the arc and burning. If you start to remove the plating, even at the microscopic level, you hasten the burning.
Is this correct?
This is my biggest concern. But the contacts being dirty and the "day" short I don't have a good contrast to confirm the original state of the contactors.
 

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In brief
1-MV is not 600V it is higher.
2-The contacts have designed mating contacts by manufacture, with coating. They do have a cycle life and will erode over the cycle time.
3-You replace contacts not clean. If you cannot get the contacts, then replace the contactor.

On a good quality contactor, you can get the components for them.

If you're burning up contacts find out why. There are many reasons. Start with the basics.

Size?
Duty cycle?
Load?
 

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Discussion Starter · #13 ·
In brief
1-MV is not 600V it is higher.
2-The contacts have designed mating contacts by manufacture, with coating. They do have a cycle life and will erode over the cycle time.
3-You replace contacts not clean. If you cannot get the contacts, then replace the contactor.

On a good quality contactor, you can get the components for them.

If you're burning up contacts find out why. There are many reasons. Start with the basics.

Size?
Duty cycle?
Load?
Second mention of coating, this is definitely noted. Do you know where I could find more information on the coating types, applications, identification, etc?

They aren't burning up, I am just trying to give love to an old machine. I have noticed blackening of the pads, but no excessive pitting/deterioration. I would just like to clean them regularly. Not to mention this seems beneficial for longevity of life cycle.

The contactors run 600v @ 18A for the duration of operation. Their is no cool down / break period for duty cycle. Just momentary on/off.
 

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Electrical contractor 37 years. Electrical inspector 2 years
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Second mention of coating, this is definitely noted. Do you know where I could find more information on the coating types, applications, identification, etc?

They aren't burning up, I am just trying to give love to an old machine. I have noticed blackening of the pads, but no excessive pitting/deterioration. I would just like to clean them regularly. Not to mention this seems beneficial for longevity of life cycle.

The contactors run 600v @ 18A for the duration of operation. Their is no cool down / break period for duty cycle. Just momentary on/off.
Years ago I was told silver but IDK for sure.
 

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Different voltages and currents use different metals for the contact surfaces, they are designed so that the arcing cleans the contact surface rather than galls it when the contacts open and close. With low voltages and currents (such as signal as you mention) it's probably less of a factor.

Seems like what you're doing would be like taking a wire wheel to your tires for better traction, you're removing tread. You may or may not improve the surface (more likely not) but you'll definitely shorten the lifespan.
 

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Second mention of coating, this is definitely noted. Do you know where I could find more information on the coating types, applications, identification, etc?

They aren't burning up, I am just trying to give love to an old machine. I have noticed blackening of the pads, but no excessive pitting/deterioration. I would just like to clean them regularly. Not to mention this seems beneficial for longevity of life cycle.

The contactors run 600v @ 18A for the duration of operation. Their is no cool down / break period for duty cycle. Just momentary on/off.
possibly where it is black it is not contacting and does not matter
if they are cycling frequently, look for Excessive pitting, other than that "Let it Be"
as mentioned, do not clean .... replace
once you clean you have destroyed the mating surface it developed when new
now it has to do some destroying to reseat itself .. this will cause much more wear
not to mention, once it finally reseats, it appears burned almost as much as before

if these contacts are actually silver, melt them off and sell for scrap when replaced
none of the contacts are silver since the early 2000's that i am aware of
 

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We did it with emery cloth glued to a flat piece of steel. Lay the steel down then hold the contact and work it against the paper to ensure its 100% flat.

If you have deiced that the contacts are burnt and need to be replaced then it really doesn't matter what you do to the old set. We could get well over 30 years out of a allen bradley 509 that's being abused. IEC and sq-D starters we just replaced the complete starter and hoped we could get a few years out of the new ones.
 

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I pretwist and then use wire nuts. Solder pots rule.
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Zog gave a great answer to this 12 years ago.


Using a file or sandpaper can cause abrasive material to fall into the mechanism, causing shorts (Files) or binding (Sandpaper).

Scotchbrite is the industry standard for dressing contacts, if necessary.

However, usually it causes more damage than good. As John mentioned contacts are typically silver plated over the copper. The reason this is done is that the material will oxodize, no matter what it is. While the conductive properties of copper and silver are similar, silver oxide is a great conductor while copper oxide is a very poor conductor. Sivler oxide looks like a brown coating on the contact surface, you do not want to remove that layer, doing so will remove some of the silver and if the copper is exposed the resulting copper oxide will lead to heating and eventual failure.

Contacts that show pitting or <50% contact area (From impression check) should be re-plated or replaced.

from this thread
 
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