Re: [TCML] Dr. Resonance inductors - 1/16th of an inch?

[David Dean <deano@xxxxxxxxxxxxxxxx>]

Thanks, Ed

On Saturday 07 March 2009 05:48:52 pm Ed Phillips wrote:
> >> I believe inductance is calculated by
> >> L= (d2 * n2)/(18*d+40*l)  (MicroHenries)
> >> where:
> >> L is inductance in micro Henrys,
> >> d is coil diameter in inches,
> >> l  is coil length in inches, and
> >> n is number of turns.
>
>     That's ONE of the several Wheeler approximations for a single-layer
> solenoid, far far from the optimum shape for a relatively low frequency
> high inductance inductor.

So it is the wrong tool for the job. Still something wrong with that javascript 
though, does not work right with the proper formula either.

> I have a University of Illinois research 
> bulletin which derives the optimum shape for an air-core power
> inductor.  Can't find it right now but as I recall the coil cross
> section is square and the ratio of outer to inner diameter is 4/3.

Sounds a lot like a Brooks coil, for which see:
http://www.fnrf.science.cmu.ac.th/theory/magnets/An%20introduction%20to%20the%20air%20cored%20coil.html


> Lots 
> of design equations and tables of measurements in it - wish I could
> figure out where I put it.
>
>     Remember that the objective here was an inductor capable of carrying
> about 1 amp - #30 wire just wouldn't hack it.
>
> Ed

later
deano

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