I've never actually heard of anyone using the silver plate to enhance
the surface conductivity with respect to skin effect, and the return on
investment so to speak, as laid out in Mike's post, is pretty accurate.
The predominant reason for silver plating bus work is that it resists
corrosion better than copper (but is cheaper than gold); when it does
oxidize it conducts more reliably than copper, and it has the lowest
electrical resistivity of any metal. This is why the contact faces only,
are typically silver plated in the induction equipment mentioned below.
Gold -is- superior for this application, if price is no object. The
conductivity is significantly lower, but the corrosion resistance is of
course improved.
Using Penetrox, or a similar product on the joints works wonders. It
penetrates the oxide, and seals out oxygen so it prevents formation of
new oxides. Certainly not as attractive as silver plate, but a really
inexpensive option.
Cheers,
Leigh
-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: January 11, 2007 12:37 AM
To: tesla@xxxxxxxxxx
Subject: Re: the mechanical engineering problem
Original poster: Mike <megavolts61@xxxxxxxxx>
Hi DC,
I'd be happy to silver plate your primary, as I am well versed
in that. I used to work in a research lab doing all kinds of
electrochemisty, including once even fixing an induction furnace
who's silver plating had tarnished away over the years and quit
working. I put a better plating on the parts than the original
manufacturer did. That's beside the point.
I deleted the earlier emails on this thread but seem to remember
you planned to run this monster at about 20kHz. Let me point out a
lil something I thought about. From the information I have, The
skin depth (based on copper, but probably close) at 10 kHz is 0.66
mm. So for fun, I did a lil caclulation based on an assumption
that the skin depth for silver at 20kHz is about 0.5 mm. I know I
should be more precise, but I'm lazy tonight.
First of all your perimeter of the bus bar is (5 + 1/4 + 5 +
1/4) * 2.54 cm/ in. or 26.67 cm. Then, 1 ft length is 12 *
2.54 or 30.48 cm, giving you an area of 812.9 sq. cm. per foot of
bus bar. Now multiply that by 0.5 mm (or 0.05cm), you get 40.645
cu. cm per foot if you wish to have ALL silver conducting. At a
diameter of 26 ft, this leads you to need pi*26*40.645 cu. cm of
silver. Multiply that by the density of 10.5g/cu. cm and divide by
31.1 grams/troy oz. This shows you will need over 1100 troy oz of
silver just for that first turn. I think you might gain about 5%
better conductance for your $$. This was just an
estimate....but you see where I'm coming from....might be a lot
cheaper to go to six inch bus bar. It also depends on how thick
you want the silver plating to be. I honestly can't say at this
moment if there's really anything to be gained by plating the bus bars.
Mike
Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
You may know this already, but when you go to silver
plate the bus bars, you can do it in your shop for a
fraction of the cost of having it electroplated, by
using Cold Amp. It's a powder and real easy to use.
We've used it in medium voltage (12,470) switchgear.
Adam
--- Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "D.C. Cox" <resonance@xxxxxxxxxxxx>
>
>
>
>
> Thanks to everyone who submitted ideas for the big
> primary coil. I
> have several ideas now and will resolve the issues
> soon.
>
> Several members suggested internal primary, but if
> there are any
> flashovers they would not be visible unless fiber
> optics were
> employed to watch for them.
>
> The idea I think we will employ (actually suggested
> by several
> members) is to use 5 inch wide x 1/4 inch copper
> ribbon buss bar and
> then silver plate it.
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