Re: magnetics design -- 60mJ energy impedance matching

On Sun, 17 May 2009 06:36:49 GMT, Jon Kirwan
<jonk@xxxxxxxxxxxxxxxxxxx> wrote:

On Sun, 17 May 2009 05:19:55 GMT, I wrote:

On Sat, 16 May 2009 21:52:48 -0700, D from BC
<myrealaddress@xxxxxxxxx> wrote:

On Sun, 17 May 2009 03:40:27 GMT, Jon Kirwan
<jonk@xxxxxxxxxxxxxxxxxxx> wrote:

<snip>

Anyway, that's what's bothering me. I'm probably missing something
terribly important. I hope so.

Thanks,
Jon

Okay. It's making more sense, now. I sat down and looked at the B/H
curves for steel and cast iron and played with some delta-B/delta-H
values taken from the curve as finite approximations for Ur. Then I
picked off the central B value, squared it, to get some Ur/B^2 figures
plotted out for various B values through to saturation. The steel
curve I was looking at flattened out at 1.6 Teslas, by the way.

What makes sense now, given the volume equation I derived above and
these figures, is that designers must almost _always_ be designing
near the saturation region; balancing windings with the effective Ur
to get the right balance between copper losses from too many windings
as the core nears saturation and air-like behavior as the field
fringes out into infinity and very few windings at low values of H,
but where the core volume is too big. Somewhere between "few
windings, horribly huge core" and "no core to speak of, but massive
windings for an air core" you get the right in-between thing.

Yes, it is balancing between the various losses versus cost, life, and
efficiency.

It's making more sense.

Simulating this design region in LTSpice is the next thing to learn
about.

Jon
.

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