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Re: Filter Choke Design

On Wed, 6 Mar 1996 tesla-at-grendel.objinc-dot-com wrote:
> >Suppose that a 100 turn choke sees:
> >10,000volts at 100kHz
> >   V x 10^
> >B= ------------------
> >    4.44 x f x N x A
> >B=22,000 gauss

Correct if you have 10kV rms voltage between the ends of the coil.
However, you may have pretty severe ringing and I'll leave speculating
that to the experts.

> Gauss???????? I thought they redefined the units for measuring magnetic flux
> as Teslas??

Many older books and lots of people still use Gauss for the unit of magnetic
flux. Some other use Teslas. 10 000 Gs = 1T. So the example above
means 2.2T.

Depending on the material that may or may not be low enough. Most ferrites
work safely without saturation up to around 2-5T depending on the
material. There may be another point to consider too: they may heat
with high frequency at some cases. Probably this does not happen with 
those applications.

Why is nobody using the setup often seen in filters ie. wind two
windings to the same core. Properly phased they will cancel each
other out when one lead makes flus +B the other is making flux -B.
The net will then be 0 naturally. Insulation problems will be a lot more 
severe to mention one problem. Coil on the other hand will get lot
smaller.
 --
See "Malin Tunic: Chemistry of structure - function references in cheese" for
further details!
Harri.Suomalainen-at-hut.fi - PGP key available by fingering haba-at-alpha.hut.fi