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Re: Electrical Properties of Aluminum and Network Analzyer was : RE: Brass



Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Dan,

At 10:48 PM 4/20/2003 -0400, you wrote:

>Terry,
>
>That test is severely flawed:
>First, we already know that for the same cross-sectional area, aluminum has
>a higher resisitivity per unit length than copper.  No need to use
>a network analyzer for this.
>Secondly, a network analyzer is not going to tell you squat about how an
>oxidized coil performs under high rf current conditions like those occurring
>in a
>tesla coil.

But it might tell me more than I know now  0:o)

>You really need to make the measurements somehow at the rated
>power levels you are going to operate at for the data to be meaningful.

The machine has input and output power measurement so it could probably 
tell the coil dissipation to within 1% percent.  I would probably have to 
make my own coils since we don't have any bare aluminum ones and they would 
not understand my wanting to order any ;-))  It can run 50 amps RMS easily, 
so if the skin depth varies at higher currents it should be sort of 
"real".  The frequency is far higher however at 13.56MHz.  If I had two 
coils I could also get them to test them on the analyzer which could show 
the whole frequency spectrum, but that would certainly be like milliwatt 
stuff.  It would be cool to try oxidized and none oxidized Al.  As Jim 
mentioned, maybe boiled Al would have a much more defined layer of oxide 
making it stable and not as lossy as just any old Al out of a junk yard.

Any "results" would be subject to many questions but it would be neat just 
to try.  I do have a 900W 350kHz generator too that maybe could do some 
thermal testing.  See how much hotter one coils gets vs. another...  But it 
only does like 5 amps.

Just sort of an idea...

Cheers,

         Terry


>The Captain
>
>
>
> > We have RF effects forcing the current to the outside and resistive
>effects
> > forcing current in....  Exactly where the current goes and what the loss
> > is, is an interesting problem I am sure ;-))  In a few days I am getting
> > some high power RF coils that are aluminum heavy plated with silver.  They
> > work well since the currents travel in the thin silver layer.  What will
>be
> > fun to see is what happens if the plating gets a crack.  We "think" it
>will
> > incinerate.  But have to see for sure.  Stay tuned...
> >
> > I or Gary Lau may be able to get two coils that are exactly the same
> > dimension but one is copper and the other aluminum and test the resistance
> > on a fancy HP machine.  Soaking or boiling the aluminum one in salt water
> > will certainly oxidize it well.  I'll ask the guys that know how to run
>the
> > HP network analyzer beast to see if that is "easy" to do.
> >
> > Cheers,
> >
> >          Terry
> >
> >