Re: Need help - winding an inductor

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, March 10, 2002 5:12 AM
Subject: Need help - winding an inductor


> Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<youngs-at-konnections-dot-net>
>
> Coilers,
>
> Please give me some ideas for winding an air core inductor of about 0.2
> Henry.  This will be used for an experimental charging reactor for a TC.
> Specifications are as follows:
>
> 1) Multi-layer air core solenoid wound with #26 wire
> 2) Needs to withstand a peak voltage gradient across the coil of 10 KV
> 3) Would like coil length, inside diameter & number of layers to give the
> most inductance per length of wire.  In other words, I would like to
> minimize the wire needed to achieve 200 milliHenry.
> 4) Must be something easy to wind and as small as practical.  (Please
don't
> suggest a large TC secondary!)
>
> Does someone have a formula for calculating the inductance of multilayer
> solenoid inductors?  I am thinking the end product will be something like
a
> woofer speaker cross-over air core inductor, for which there should be
> design information available.

http://home.earthlink-dot-net/~jimlux/hv/wheeler.htm has the equations...
You can use Excel in "goal finding" mode to optimize a design.


Some things to think about...

Winding several sort of thin but wide coils, and then stacking them with a
thin insulating (polyethylene) layer inbetween is a good way to improve HV
breakdown. Say you wound 5 subcoils, each 40 mH.. in series, isolated it
would be 200 mH... in practice, since they are reasonably close to each
other, you could wind 5 subcoils of say, 10 mH each.. you'll have to run the
numbers.  Each coil would only have to hold off 1/5 of the total voltage...

You should take a look at that company that sells tapewound air core
inductors (I can't recall the name, but I posted a link to them last week..)
Very reasonable prices (<$20) and they should hold off a bunch o' volts,
given their construction.

>
> As a sanity check, I measured a partial spool of #26 enameled wire.
> Solenoid measures 9.1 cm long by 8.9 cm dia by 1.2 cm winding thickness.
> This has an inductance of 1.35 Henry and weighs about 4.3 pounds including
> the plastic reel.

Inductance, roughly, goes as the square of number of turns... So, if the
whole spool is 1.35 and you need 0.20, that's a ratio of about 7:1... take
the square root, and it looks like you'd want about 1/(2.5) of the spool..
give or take...

You know, an iron core would go a LONG way towards reducing the amount of
copper you'll need, and iron is a lot cheaper than copper.


>
> Thanks for any help you can give,
> --Steve
>
>
>
>
>