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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Ferrite E-core properties
Date: Wed, 18 Sep 2002 00:58:35 GMT
NNTP-Posting-Date: Tue, 17 Sep 2002 17:58:35 PDT
> In article <firstname.lastname@example.org>, email@example.com
> (Tom Bruhns) wrote:
> > Surely you can determine an Al value by measuring the inductance of a
> > test winding, and you can get a good idea of the saturation
> > characteristics by monitoring the current as a function of time as you
> > apply a square wave of voltage to your test winding. Start at low
> > voltage and work up, till you see a significant deviation from
> > linearity in the current's triangle wave. You can use a half-bridge
> > driving your winding through a capacitor, to keep DC out of the
> > winding. (IR has some very easy-to-use self-oscillating half-bridge
> > parts that can make that task easy.) However, you'd also want to know
> > something about core loss at your intended operating frequency, since
> > core excitation is generally limited by temperature rise rather than
> > saturation at typical switcher operating frequencies. A thermistor
> > (or equiv.) glued to the core might tell you enough about core loss.
> > Cheers,
> > Tom
> > Mike Newman wrote in message
> > > I've accumulated a number of ferrite E-cores from PC PSU's that I'd
> > > like to use in some switched mode power supplies.
> > >
> > > Without any data on these cores, how can I determine their magnetic
> > > properties, so that they can be designed into the SMPSs.
> > >
> > > I've a scope and AF generator, and can homebrew any other test gear
> > > required.
> > >
> > > I'd be grateful for some ideas.
> > >
> > > MikeN
> I saw the other responses. Am I way off in assuming that you would want a
> b/h curve?
Not entirely. A B/H curve is nice and easy to get but the methods
suggested get the most important information (inductance of a test coil
and saturation current for the test coil) in one simple test.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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