Re: OLTC update

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Matt,

On 22 Sep 2002, at 20:46, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Mddeming-at-aol-dot-com>
> 
> In a message dated 9/22/02 7:54:53 PM Eastern Daylight Time, tesla-at-pupman-dot-com
> writes:
> 
> 
> >
> > > I am interested if anyone has any tips on how to wind a 34mH air core
> > > inductor with #20 wire using the least amount of wire (least resistance).
> > > I figure a very short large diameter coil?
> >
> > The highest inductance per length of wire is scored with highest 
> > coupling between all turns. Therefore, a multi-layer coil with the 
> > number of layers = number of turns per layer is the way to go.
> 
> 
> Hi All,
> It can be shown that the highest achievable inductance for a given length of
> wire for a helical coil occurs when Height= 0.9 x Radius. There is a similar
> maximum for a flat coil at 8R=11B. I can send you a paper showing the
> derivations, if you desire.
> Matt D. 

I derived it myself some time ago ;)  However, the question was about 
maximum inductance for a length of wire which translates the query 
into the optimum coil shape which is neither a helix or flat spiral.

Regards,
Malcolm