Re: Optimum coil design?

From: John Popelish (jpopelish_at_rica.net)
Date: 08/25/04 

Date: Wed, 25 Aug 2004 19:19:30 -0400

Active8 wrote:
>
> On Wed, 25 Aug 2004 12:47:44 -0400, John Popelish wrote:
>
> > Winfield Hill wrote:
> >>
> >> Calin Dorohoi wrote...
> >>>
> >>> I would like to know how to compute the shortest wire length
> >>> required to build a specific inductance given a certain wire
> >>> diameter. My question refers especially to multi-layer
> >>> air-core coils.
> >>
> >> This is a problem that out distant forefathers solved long ago.
> >>
> >> The optimum highest inductance to wire-length ratio occurs in the
> >> Brooks inductor. Its windings are square in cross section and have
> >> a roughly 3:1 ratio of mean-diameter to length.
> > (snip)
> >
> > What about cross sections of some other shape than square? Round,
> > triangular or elliptical, for example?
>
> The cross section is not that of the winding form but that which is
> formed by the turns - cut the tube into two semi-circular troughs,
> IOW. So you're stuck with square, rectangular, and triangular for
> all practical purposes. That's the way the integrations are
> performed to calculate the inductance.
>
> That's 3 of us that need Grover ;) I doubt it's worth the time to
> design coils as physics problems.
>
> I just took the inductance formula for a solenoid and rearranged it
> so I could differentiate wire length wrt coil length and set it to
> zero. It don't work! Either L must be 0 or turns must be infinite.
>
> Too many variables. Maybe it's doable, but today ain't my day for
> this. Poorly specified problem, too. Sounds like homework.

I am talking about the shape of the cross section of the winding.
Just because you can not think of a good way to wind wire in an
arbitrary winding cross section does not mean that the question is
pointless. 

-- 
John Popelish

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