[sdiy] Transformer question ( skin effect )

[Tom Arnold]

Working on a switching power supply.  Not repair but construction from
scratch.  Start by gutting a PC power supply for the transformers. Its a
switch supply with a switching freq of approx 35khz.

Primary gets wound with 10 turns of parallel 3x24ga wire and secondary gets 
wound with 9 turns of parallel 4x24ga wire.  For added current handling there 
is a suggestion to wind more on the secondary, perhaps 8x24ga.   

Okay, question time.  I could use heavier wire instead of more strands.
24ga was chosen for ease of winding not current handling, but I have to
wonder, if I went to 18ga wire which is basically twice the diameter, do I
actually gain current handling linearly?  I would *assume* at 35khz
skin-effect will be fairly pronounced and circumference is twice that of
24ga so if I wanted to double the secondary I'd think that going to 18ga
wire would be suitable, but it looks like going with maybe 1.5 times the
number of parallel 22ga windings would actually work better.  I just don't 
know and I haven't found good reading material yet.

Hrm.  Now I've just done more reading and run through a skin effect
calculator and it looks like at 35khz, skin depth with be .35mm which would
basically leave the center .3mm of an 18ga wire "unused" and perhaps being
patient and ordering some 22ga wire would be my best choice. I'd like to be
impatient and wind with what I have, which is 18ga but perhaps this isn't
the best choice and I don't have enough 24ga to double the windings.

Any guidance from the learned ones?

-- 
 -----------------------------------------------------------------
 - Tom Arnold       -  Free Synth DIY webspace http://www.sdiy.org 
 - SynthGeek        -  "...is it a virus, a drug, or a religion?"
 - AF6YW            -  Juanita Shrugs. "What's the difference? 
 --------------------         -- Neal Stephenson,  Snow Crash