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From: "Frithiof Andreas Jensen"
Subject: Re: SMPS transformer core power throughput calculation
Date: Mon, 16 Sep 2002 14:47:25 +0200
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"Michael Denner" wrote in message
> A formula must exist because the Magnetic designer Demo program from
> intusoft has just that very feature.
There is no Grand Unified Theory in transformer design!
One usually checks the material to find out what the acceptable flux density
should be, then one chooses a core, calculates how many turns the primary
would need; check if there is room for the secondaries - they should take
the same volume as the primary, since both set of windings are handling the
same power etc... tedious!
Finally, the temparature is estimated and a prototype is built.
When I did this, I usually did 3-6 "paper designs" and 1-2 hand-wound
I used Faraday's equation and various application notes - Unitrode, now TI,
did some good papers on magnetics design. There are some IEEE papers on
numeric design methods, but most seem to rely on information not available
or deducible from the manufacturers datasheets.
And most do not consider temperature, which is the real power limit for a
> How is this calculated?.
Assumptions are made on losses and temperature dissipation; but since you do
not know what they are, I would be careful about using such a program.
> Does anyone have such an equation/formula?
There is another program at www.epcos.com -> design tools;
Maybe it works ;-)
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