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Re: LOW Inductance Ballast



---------- Forwarded message ----------
Date: Thu, 9 Oct 1997 19:08:00 -0400
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: LOW Inductance Ballast 


> 
> ---------- Forwarded message ----------
> Date: Thu, 9 Oct 1997 16:08:08 +0100
> From: Julian Green <julian-at-kbss.bt.co.uk>
> To: tesla-at-pupman-dot-com
> Subject: Re: LOW Inductance Ballast
> 
SNIP!
> > 
> > 
> Yes I know that there is no inductance even if the extension lead
remains
> rolled up because the 'go' and 'return' conductive paths run
parallel
> and any magnetic fields generated by one conductor are cancelled
out 
> by the other.   If however you run too much power down a coiled 
> extension lead it gets hot and you end up melting the insulation.
> 
> I did this and was completely unaware of what was happening at the 
> time.   The outer layers exposed to the air only got warm, but the 
> layers below had melted and formed a solid lump of PCV.    My
extension 
> lead was ruined.
> 
> Julian Green

Julian,
In a case like that you are best off using the technique I described
(or the bifilar method with separate "hot" and "return" wires) but
with the wire wound around an open frame made of something like wood
or PVC pipes. Allow maximum air flow over BOTH surfaces. You can make
the thing more compact if you use multiple layers, but with a spacing
of about 1/2" or more between layers. A muffin fan can be attached to
one of the ends to force cooling air into the center, where it will
then filter out. It's bigger, but she won't melt on you. Of course,
if you don't mind lots and lots of loose wire all over the place,
then just keep using your current setup. The methods we use are often
more a matter of convenience or personal preference as much as
anything else.

By the way, if you were to use wire with no insulation in such a
frame, the cooling would be greatly facilitated. You would have to
allow greater spacing between wires to allow for "slump" when the
wires get hot.

Fr. Tom McGahee