Re: [TCML] Reality or Artifact

[mddeming@xxxxxxx]

Hi Bart, 

Interesting charts. The Ldc peaks at ~0.42 close enough to the 0.45 of the quick and dirty, but Les peak is way off at 0.20.  Seems like a secondary coil with an h/d ratio of 0.20 would be highly impractical for most peoples' TC purposes: long sparks.  I was a little surprised that the Ldc curve was so flat. near the max value.

Thanks for the info.

Matt D.





-----Original Message-----
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Thu, Jun 3, 2010 9:35 pm
Subject: Re: [TCML] Reality or Artifact


Hi Matt, 
 
Lucky for you, I already performed that nasty daunting task ;-) . I went through Javatc and setup h/d ratios from 0.01 up to 1.0 in .01 increments, found max inductance and logged data. What I was looking at was the difference between low and high frequency inductance (Ldc, Les) and how they would track. 
 
Here's a graph of that endeavor 
http://www.classictesla.com/temp/MaxL.gif 
 
The excel file is here with the data 
http://www.classictesla.com/temp/max_inductance_csv.xls 
 
Not sure if this helps at all, but if so, great. 
 
Best regards, 
Bart 
 
mddeming@xxxxxxx wrote: 
> Hi All, 
> > In the classic, quick and dirty formula for the calculation of solenoid inductance, > > L=(Nr)^2/(9r+10h) > it can be shown with a little Calculus and Algebra that the maximum inductance for a given length of wire occurs when h=0.9r. This formula was originally derived, however, for "long" solenoids but the calculation results in what may be described as a rather "short" solenoid. The maximum may be an artifact of the approximation. Does anyone know the range over which the formula is valid and if there is an actual maximum at or near this ratio (h/d = 0.45)? If not, I suppose numerous iterations of Javatc could be plotted, but there again, what is validity range of Javatc's approximations? Perhaps the next step would be for me to bring the question to the "High-Mages" of TSSP. 
> 
> Matt D. 
> 
> 
> 
> 
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