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Re: Transformer basics

[snip on a section taling about winding hv transformers]

 I don't think you need to do anything special like layering
>insulation between windings.  When you unpot neon sign transformers, they
>just have miles of fine wire wound on layer after layer.  I would give the
>finished product a good varnishing - or submerge it in oil.
>
>Ed Sonderman
>

Wrong!  Neon transformers do have layer after layer of wire, but there is a 
layer of insulating paper between each layer of wire.  If you tear apart a 
pole pig, you will find the same thing, layer upon layer of wire, but each 
layer has a very heavy insulating paper layer between them.  One might think 
paper is not a good insulator, but the voltage difference between any two 
adjacent layers of wire is not very great, and the oil soaked paper works well.

Put a layer of insulation between each layer of wire or your transformer 
will fail.  I can also relay a bit of first-hand experience on building your 
own transformer.  I tried using teflon as the insulation between layers.  It 
is too soft and too slippery.  You want the inter-layer insulation to be 
stiff and flat.  If the insulation has too much "give" in it, then bumps or 
other winding imperfections show up in the next layer of wire and propagate 
and the initial small imperfection will show up worse and worse as you add 
layers of wire.

I hand wound a 2 kva 7500 volt transformer, I used teflon, and it worked for 
only a short time.  I still have it, I put so much work into it I don't have 
the heart to throw it away.

Bert