On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A


Well, it's theoretically possible to build a transformer from scratch,
BUT! You have to make a bobbin, find a lamination vendor that will sell
you only a few hundred lams, assemble the damn thing, hypot it, and
test it, to determine that you didn't get the lams tight enough so your
leakage inductance is unacceptable, redo it, redo the windings, interleave
the lams again, whack it a few times, pot it - - -

After about two weeks of this crap, you might want to go check surplus
dealers - they usually have surprisingly good bargains on transformere -
sometimes, you can buy them by the pound.

Good Luck!
Rich