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From: email@example.com (Tom Bruhns)
Subject: Re: Ferrite E-core properties
Date: 17 Sep 2002 11:41:38 -0700
NNTP-Posting-Date: 17 Sep 2002 18:41:38 GMT
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.
Mike Newman wrote in message news:...
> 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
> I'd be grateful for some ideas.
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