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Re: Aluminium aka Aluminum Wire (fwd)



---------- Forwarded message ----------
Date: Mon, 01 Oct 2007 23:53:09 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Aluminium aka Aluminum Wire (fwd)

Hi Gary,

Yes, I knew what you were disputing, but I also wanted to "not" head 
towards the opposite end of the spectrum where aluminum becomes ok as a 
"blanket statement" like what was done about aluminum stated as bad for 
RF. It is dependent on the application, frequency, sD, current, etc.. 
Any conductor (even silver) might suck under the right conditions.

Regarding secondary losses, the losses will increase on the secondary 
side with Al vs Cu. But yes, it may be of no real concern. I believe it 
can make a slight difference for a typical Tesla coil. The primary side 
can see losses due to the current, but even in that scenario, it might 
not be a concern as it's dependent on the energy, current over time, and 
the material.

I don't like guessing. Even empirical data is based on limitations of 
the experiment. Someone recently asked me about equating primary losses, 
but I can't do it accurately (yet). Although we do have approximations, 
it really is important to check against measurement. For the secondary 
coil, I had that data, but don't have anything near that for the 
primary. I expect sometime in near future we will gather some good data 
on primary losses.

My gut tells me that in many primary windings, Al would do ok, but I 
also expect it nears a border line. Losses will ultimately end up 
thermal. Even copper winding primary's heat up under the right 
conditions. RF is part of what causes it. Even coupling plays a major 
role (time and energy will define current through a material). Those 
same primary's would be worse if Al. What is good about non-ferrous 
materials (regardless of what they are) is that their inductance is 
relatively unchanged (which is why they do well for tuning). Throw an 
iron primary together and not only will heat be a big problem, but the 
inductance will vary with the change in current. The later is of course 
never realized and is more or less just an academic calculation (the 
heat is what people realize).

Take care,
Bart

Tesla list wrote:

>---------- Forwarded message ----------
>Date: Mon, 1 Oct 2007 09:46:06 -0400
>From: "Lau, Gary" <Gary.Lau@xxxxxx>
>To: Tesla list <tesla@xxxxxxxxxx>
>Subject: RE: Aluminium aka Aluminum Wire (fwd)
>
>Hi Bart:
>
>I agree that the losses in short fat blocks are negligible, regardless
>of the material choice.  If folks were considering using tubing or wire
>made of brass for a primary conductor, then this would be a concern
>(folks considering using bronze weatherstripping for a primary - take
>note!).  My point was actually directed at those who suggested that
>losses in RSG electrode holders made of aluminum would be unsuitable,
>and that brass would be a superior choice.  Practically speaking, it
>makes no difference.  But if you go through the numbers, aluminum is
>better from the electrical perspective.  But yes, brass looks cooler.
>
>Why would the secondary 1000-turn recommendation change if AL was used?
>I'm not sure that resistive losses in the secondary are even terribly
>important.  I think experiments with winding a bifilar secondary
>(essentially keeping inductance unchanged but reducing resistance)
>showed little benefit.  And I think Terry performed a Spice simulation
>modeling the losses in the various parts of a coil, and the resistive
>losses in the secondary were a relatively minor contributor.   Primary
>losses however were critical.
>
>Regards, Gary Lau
>MA, USA
>
>  
>
>>From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>>To: Tesla list <tesla@xxxxxxxxxx>
>>Subject: Re: Aluminium aka Aluminum Wire (fwd)
>>
>>Very true Gary. But considering we use them mainly as dissipation
>>    
>>
>mass,
>  
>
>>they serve the purpose well. In short fat blocks like that, almost
>>anything will do (even iron masses). It's when we start winding coils
>>with these materials that we experience losses we can measure. I have
>>    
>>
>no
>  
>
>>doubt we can wind a secondary from Al magnet wire and have it perform
>>well, but the design itself will be different from what we are use to
>>(that thousand turn recommendation will change).
>>
>>There's no doubt that RF losses will be at least 150% higher, but in
>>    
>>
>the
>  
>
>>tank discharge arena, it's not a factor worth discussing. If you look
>>    
>>
>at
>  
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>>the losses on the total system scale, this particular loss in the
>>primary circuit is extremely negligible and why the RF with aluminum
>>    
>>
>is
>  
>
>>interpreted as a myth hoax.
>>
>>But, insert those losses to the secondary side, and then we need to
>>start looking a little closer. In many cases it will not be a problem
>>(many secondary geometry's can be made rather efficient with aluminum
>>wire), but there are situations where it will drop output as compared
>>    
>>
>to
>  
>
>>a copper winding.
>>
>>No matter what material we use for wire, the conductance of that
>>material is just as important as the length and size of the conductor.
>>We can't change physics (just do our best to understand and design
>>accordingly). In some cases, aluminum will be a poor choice and copper
>>will be far better. In other cases, aluminum will be just fine for the
>>application. The real task is deciding when the one with lesser
>>conductance is ok (and when it is not).
>>
>>Take care,
>>Bart
>>
>>Tesla list wrote:
>>
>>    
>>
>>>---------- Forwarded message ----------
>>>Date: Sun, 30 Sep 2007 21:09:28 -0400
>>>From: "Lau, Gary" <Gary.Lau@xxxxxx>
>>>To: Tesla list <tesla@xxxxxxxxxx>
>>>Subject: RE: Aluminium aka Aluminum Wire (fwd)
>>>
>>>Hi Bart:
>>>
>>>Thanks, that's a great link.  I never looked too closely at the
>>>      
>>>
>relative
>  
>
>>>resistivities before.  In addition to the wide range of alloy
>>>resistivities, I was also surprised with how poorly brass compares to
>>>aluminum - TWICE the resistance!
>>>
>>>Regards, Gary Lau
>>>MA, USA
>>>
>>>
>>>
>>>      
>>>
>>>>From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>>>>To: tesla@xxxxxxxxxx
>>>>Subject: Re: Aluminium aka Aluminum Wire (fwd)
>>>>
>>>>I goofed the link. Left out a "d" in "eddy". Here's the correct
>>>>        
>>>>
>link.
>  
>
>>>>http://www.eddy-current.com/condres.htm
>>>>
>>>>
>>>>        
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>      
>>>
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