On Fri, 29 Jun 2012 19:44:08 -0700, josephkk
wrote:

On Thu, 14 Jun 2012 18:45:50 -0500, "Tim Williams"
wrote:

"Robert Baer" wrote in message
alnet...
Try amorphous or nanocrystalline cores, too. They switch quite quickly.
I've built a toy circuit that generated enough harmonics to cause itself
to ring a bit; the risetime was under 1us.

Where can i buy some?
Are there various sizes available?

You can find a small one in any computer PSU: they use a saturable core
(square B-H curve) to regulate the 3.3V supply off the 5V winding. (Thanks
to separate regulation, and the high gain of the TL431, the 3.3V supply has
substantially better regulation than the 5 or 12V rails!)

I have an issue he Square loop (square B-H curve) is not the same as
saturable core at all.

Square B-H curve:
http://info.ee.surrey.ac.uk/Workshop...t/results.html

Saturable reactor (and magnetic amplifier):
http://www.tpub.com/neets/book8/32m.htm
http://www.toshiba.com/taec/components/Generic/M1.pdf
The best saturable reactors / magnetic amplifiers want trapezoidal loops
with significant slant on the right and left sides.

OOps make that rhombic (~parallel sides).

@Robert
Simple circuit to plot B-H curves:
http://info.ee.surrey.ac.uk/Workshop...Ckt/index.html

They're sometimes used in line filters too, where they offer unusually low
cutoff frequencies. The average COTS line filter peaks around 10MHz;
amorphous/nano cores peak around 0.1-1MHz instead. Look for unusually heavy
epoxy or plastic-cased cores; occasionally the plastic case cores hold a
Finemet or ferrite toroid, so peek inside if you can open it easily.

Most core suppliers have them; Elna Magnetics carries VAC, Adams Magnetic
carries Metglas/HMG. Check also with any local power control reps, might
get some samples or something. There's also a few sitting he
http://www.surplussales.com/Inductor...FerToro-3.html
I picked up a few of the 50B12-1Ds (square permalloy IIRC), which I would
guess might switch 100W each if you push 'em. I ran a few watts through one
as a test:
http://myweb.msoe.edu/williamstm/Ima...g_Amp_Test.png

Tim