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Re: [TCML] primary material? (interview)

I don't know if DC has tried it or not, but there is certainly truth to higher resistance, peak currents, heating. Ed Phillips did measure Al and Cu wound coils for Q, R, etc. TCML archives (final report). What was found was expected. There is a an overall blanket myth with aluminum and Tesla coils when it comes to the electrical properties. It is true that Al has higher R of a ratio in the neighborhood of 1.6, but these properties are linear and increasing conductor size will bring it up to par with Cu (these functions are linear).
The real problem I think for Al primaries is oxidation and the effects this has with tap connections, galvanic corrosion, etc.. With some maintenance, that should be manageable. Given the prices of metals these days, I suspect we will see more and more use of aluminum and we will also see "how" to use it in the correct application as experience unfolds. For example, if one were to use Al as a spark gap electrode material, then you would have some real issues (none of which are electrical but rather mechanical such as heat, pitting, quenching, etc.).
The overwhelming losses are in the gap. The losses in the tank are small in comparison. The use of Al and it's electrical properties requires putting the coil itself as a whole into perspective. There is no doubt that copper is a better choice electrically size for size. But that isn't the issue. The issue is if it is a viable alternative if material costs force it's use for some coilers.
Even for super coils where the cost of material is substantial, it may be a significant cost savings, or similar if manufacturing a high number of coils. Let's see, 35" sparks versus 40" at Al versus Cu cost ratio of 2.67? Maintain margins and move the savings to the customer (quantity of sales increase, profits increase). So, did I talk anyone into it? :-D 

Regards,
Bart

dr.hankenstein@xxxxxxxxxxxxx wrote:
Have you actually tried comparing the two materials side by side? 


[Original Message]
From: DC Cox <resonance@xxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Date: 7/18/2008 2:34:41 PM
Subject: Re: [TCML] primary material? (interview)

Bart & Gary are correct --- alum is not the best choice.  Alum can be used
for high voltage transmission lines cross country because it's resistance

is

reasonable low at the 60 Hz frequency, but at RF frequencies that Tesla
coils operate at, it's a very poor choice.  In the primary it will cause
excessive resistance at operating frequency frequencies which reduces the
overall peak currents.  Remember high peak currents in the primary (which

is

why we used pulse caps -- to get a high peak current) produce powerful
magnetic fields which encompass the secondary coil.  When this magnetic
field collapses rapidly, a high voltage pulse is produced in the sec coil.
With a weaker pri current, the sec coil will not receive as much energy

thus

producing a weaker spark --- certainly not as bright as copper.

Happy sparkin' with copper,

Dr. Resonance

On Fri, Jul 18, 2008 at 12:11 PM, John Matok <jmatoknoon@xxxxxxxxx> wrote:


What affect would aluminum have on my performance?  If it's cheaper, why
wouldn't everyone use it?

Nicholas

On 7/17/08, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:

Hi Nicholas,

Yes, all metals are up in price everywhere. It makes choices more
difficult. Copper is up about 50 cents/lb as well as aluminum. The
difference is $4/lb with copper versus say $1.50/lb with aluminum

(just

looking at scrap rates). Anyway, you could build the primary with

aluminum

tubing. It's sold in the hardware stores also and is certainly an
alternative.

Take care,
Bart

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