"John Woodgate" wrote in message
...
In message , dated Tue, 8 Aug
2006, Mark Fortune writes

So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

You need more than 5 A AC to get 5 A DC. The rough rule is that a bridge
rectifier needs a factor of 1.6 times, but with modern huge filter caps,
think of at least 1.8 times. That's a BIG transformer, with THICK
secondary wire. Not a project to learn on, I would say.

It's not even easy to buy parts for transformers now. Maplin used to do
kits - bobbins, laminations etc. , but not now.

To learn about transformer design, you need a textbook and one of the best
is a classic - Radio Designer's Handbook, by F Langford Smith, which was
reprinted by Newnes (Butterworth-Heinemann/Reed) a few years ago. ISBN0
7506 3635 1.

Modern core material (silicon-iron) is better than the materials mentioned
in the book. You may be able to get the information on current materials
(maximum recommended induction, core loss power/kg, magnetizing VA/kg)
from the web.
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

You can't beat a microwave oven transformer with a secondary transplant!