Why must Copper Bus Bar be Tin Plated?

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A. Hi Gunjan. Sorry but I don't understand the question. To my knowledge unplated aluminum busbar is not really satisfactory, although I have seen it used with No-Ox-Id compound for joints permanently bolted to copper. I've never personally seen "bimetallic strips" in any joint, although this 3rd asking of the same question might indicate that maybe I'm just ignorant about a commonplace approach :-)

Regards,

A. Hi Simphiwe. Sorry but I don't quite understand. Please explain what you are doing. Thanks.

Regards,

A. If you're talking about rinsing, it's important to remove the plating chemicals. Not only is it important to ensure quality, it is also for safety and many other reasons. It's not a huge danger but rinsing parts after plating helps keep the workplace clean and provides safety for the people using the items amongst multiple other reasons.

A. Hi Shabeeb. Tin plating will improve the current flow because the tin does not oxidize as badly as the unplated copper, so it makes a better contact surface.

Regards,

A. Hi Asif. Zinc plating will form gummy, resistive, corrosion products. Zinc is certainly not an acceptable plating for bus bars. Sorry.

Regards,

A. Hello Jack. Very high frequency currents do tend to travel on the "skin" of a conductor rather than through it's core. But the study of that phenomenon is an electrical engineering discipline which is a subject of greater depth than can be handled here, off-topic for this metal finishing site, and probably not what you were asking anyway :-)
I only mention it to not mislead people who may have found this page because of the search term "skin effect", which we are using in a different way than they might.

We are talking here about bus bars, and they are used for DC current or low frequency AC current, where the current flows through the bar, not on its skin. The resistance of a bus bar, and thus its current carrying capacity, are related to its resistivity as follows: Resistance = resistivity X length ÷ cross-sectional Area.

Since 99.9%+ percent of the cross sectional area of the bus bar is copper, the bus bar's current carrying capacity is not measurably increased or reduced by plating the bar with another material.

However, getting the current into and out of the bar requires that the contact faces be conductive rather than resistive, and silver or tin plating will do a better job than copper for the reasons already discussed on this page, offering a less oxidized skin. Remember that when you are calculating the resistance across the joint rather than along the length of the bar, per "Resistance = resistivity X length ÷ cross-sectional Area", now "A" is the cross sectional area of the joint and "length" is the thickness of the plating. So this piece of the Resistance is extremely minor because "length", the thickness of the plating, is next to nothing. Good luck.

Regards,

A. Hi Antoino. I have a good deal of experience in electroplating shop environments, and a small amount as an amateur electrician. But I am not qualified to comment on codes or best practices in your field. All I can say is that, if you are not in a cleanroom environment (which might discourage use of compounds), and there is no other reason to specifically discourage joint compounds, it would seem that electrical joint compound is always a good idea.

Regards,

A. Hi Paul. I doubt it, and I've never personally heard of it.

Regards,

A. Hi Sayed. I would not anticipate any need for de-rating based on my understanding of the situation. However, there still may be codes or "best practices" that I would not be aware of since large horsepower variable frequency drive installations are not my field.

Regards,

A. Hi Bibin. I can't answer that question and I doubt that anyone can because you seem to be asking about job requirements or specification requirements rather than a technology question. But certainly I would expect an epoxy coating to deliver even better corrosion resistance than tin plating. Best of luck.

Regards,

A. Tin will actually slightly increase the conductivity of the buss bar because you are adding metal.
Conversely, powder coat is an insulator and will not let the bus bar dissipate the heat to the atmosphere as well as the temp goes up, so does the resistance which will generate more heat. So, your operation will probably be less efficient.

A. Hi Ahmed. Our focus is finishing and I know little about copper smelting. But the conductivity of copper declines drastically with even a very small amount of contamination because any impurity interrupts the travel of the free electrons. Are you absolutely sure the copper is electrolytically pure?

Regards,

A. Hi Nurul. No, the bus bars should not be insulated. But the bus bars are not the problem; the problem is that the surroundings are very wet, and you should examine carefully any assumptions about what conditions are unavoidable. Please see my article "Plating Shops for the New Millennium". Good luck.

Regards,

A. Hi Shekhar. We have posted your inquiry and hopefully someone will help. My experience is in metal finishing, not switchgear design, although it sounds like the conductors are probably too small for the current they are carrying.

Regards,

A. Hi Chris. Again, I don't portray myself as an expert in such subjects by any means ... but I don't see any need to plate the copper. Make sure, of course, that you are using electrolytic grade copper as even a small amount of impurities has a devastating effect on electrical conductivity.

Regards,

A. Hi Manas. I know nothing of SF6 switchgear, but certainly any joints would seem to benefit from tin plating irrespective of what medium the joint is in, because you will not be manufacturing the copper and assembling the joint within an SF6 environment, but out in the open.

Please try to detail your actual situation rather than casting the proposition in the abstract with sentence fragments :-)
There would seem to be no air cooling within a pressurized SF6 environment, so presumably you must de-rate accordingly. Good luck!

Regards,

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Ed. note Aug 2018: The illustrated paper is no longer available from the original source, but can be found at archive.org by inserting its original URL, viz., http://www.tdeurope.eu/data/file/Environment-Sustainabilty-Approach-Capiel-HV-Part-D-Switchgear-and-SF6-Gas.pdf

A. Good day Abhilash.

I think you should consider the current carrying capability of stainless vs. copper buss bar. The "electric transfer efficiency" of stainless is much lower than that of copper.
Connections can be clamped or bolted with the use of an oxide grease. They can also be clamped or bolted and soldered.
Hope this was helpful.

Regards,

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A. Hi Abhilesh. I think that Eric was suggesting that stainless steel is not a very good bus bar substrate material -- it's current carrying capacity is only about 10% of the current carrying capacity of copper bus bar. But if you will be using stainless steel anyway, yes, it must be plated.

Copper plating should be sufficient for a 12 V power supply situation if the connection is tightly bolted, and a compound is used. But copper plating the bus bar, and then silver plating all of the contact surfaces would be better. Good luck.

Regards,

A. Hi Murthy. You're the second person to ask that this week, and my answer until I hear otherwise is that I don't know why everyday silver polish (used for flatware) could not do this job. If you google "MSDS silver polish" you will see lists of important ingredients. Good luck.

Regards,