[TCML] ARSG Design
Gary.Lau at hp.com
Fri Jul 10 11:03:34 MDT 2009
I strongly disagree with your beliefs and advice concerning aluminum conductivity.
Where would you suggest one look to find conductivity vs. frequency data that supports your statements? Where did you find this? Really, I'd like to know. I can provide one place - experimental data of measured AC resistance for various primary conductors over the range of 40KHz to 800KHz. I performed these measurements several years ago, posted the results on my web site at http://www.laushaus.com/tesla/primary_resistance.htm, and this has been discussed on this List many times in the past. It clearly shows that for similar conductor geometries, aluminum behaves no differently than copper. Baring silver, copper is the best conductor. Aluminum has 61% of copper's conductivity, while brass has only 28%. Aluminum is clearly superior, and conductivity is not frequency dependant. There is NOTHING wrong with using aluminum in a Tesla coil, beyond it being inferior by 39% compared to copper. Suggestions that skin effect will be problematic are unsupported.
Having said all that, the material choice for the electrode material itself is governed by very different issues. Aluminum is simply out of the question, not because of electrical conductivity, but because it's soft with a low melting point. It will be blasted away much too quickly. I'm not sure how brass fares relative to copper, but tungsten is the clear favorite.
Regards, Gary Lau
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of DC Cox
> Sent: Friday, July 10, 2009 11:46 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] ARSG Design
> Check out the conductivity values for brass vs. aluminum at your designed
> resonant freq. You will find brass to be the clear winner.
> Alum is only acceptable at 60 Hz power freqs. Alum at your res freq will
> limit the peak currents, which you want to be a maxiumum value for
> almost any RF design.
> The current in a series circuit is always limited by the max resistance
> component at all points in the circuit. Even small losses
> begin to rapidly add up at RF frequencies.
> Dr. Resonance
> On Thu, Jul 9, 2009 at 8:01 PM, Andrew Robinson <teslamad at aol.com> wrote:
> > Check out these designs, I need some advice.
> > Complete assembly: http://host.teslamad.com/assembly.jpg
> > Stationary electrode insulator: http://host.teslamad.com/Insulator.PDF
> > Stationary electrode:
> > http://host.teslamad.com/Electrode.PDF
> > Rotary Disc:
> > http://host.teslamad.com/Disk.PDF
> > and ring for back of disc: http://host.teslamad.com/Ring.PDF
> > The stationary electrodes were going to be made of brass as was the
> > conducting ring to connect the rotary electrodes, but I started thinking...
> > Aluminum is probably a lot cheaper. Can anyone give me a good reason as to
> > why I wouldn't want to use Al. Guess the question really is, why wouldn't I
> > want to use Al. Its a better conductor than brass but softer if memory
> > serves me correctly. Thanks for the input.
> > Andrew Robinson
> > www.teslamad.com
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