Re: how to calculate turns reqd for chokes?

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

Original poster: "Jan Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>


> Are there simple formulas available to calculate the number
> of turns required to create a choke of a specific value?

The wire gauge you choose depends on the current, and how much heating you
find acceptable.
 http://www.epanorama-dot-net/documents/wiring/wire_resistance.html

Formulas and more infos
 http://www.steward-dot-com/Steward/Technical_Info.asp
 ("Use of ferrites in EMI suppression" and "Design formulas")

The "design forumlas" part is probably what you want. Remember to use
metric units.

And maybe you'll find the articles at
 http://focus.ti-dot-com/docs/training/catalog/events/event.jhtml?sku=SEM401014
interesting and helpful. Although those papers are more with an eye on
switch mode power supply transformers. But even so, magnetics are
still magnetics... :o)

Once you know "x material" you can look up its properties in the tables
(t.ex. manufacturers website?), and plug it in to the formula(s).

> plus a knowledge of inductance would be very helpful...
> i could build/design
> * chokes for current limiting, chokes for filtering,

For 50/60Hz you better use standard ferro transformer cores, not ferrite
cores. And ferrites for RF filtering.

> * build my own KICKA** Xfmr.

You mean an induction coil?

Basically, you need very HV insulation, a few pri turns, and a _lot_ of
secondary turns. Not much of magnetics design, there - luckily. :o)
http://chem.ch.huji.ac.il/~eugeniik/instruments/archaic/induction_coils.htm

Or just get a car ignition transformer, and place it inside a
fake "Ruhmkorff coil" - that's easier than winding a real coil by hand. :-)

cheers,

 - Jan

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