Re: Essex magnet wire

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gary Johnson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <gjohnson-at-ksu.edu>

Duncan:

Thanks for the suggestion about shunt resistance.  My thought is that since
the 1994 and 1997 Heavy Soderon coatings were different, the problem was not
just outside the dielectric. If water actually soaked into the dielectric,
it could easily explain the observed losses.  If the surface became
conductive, there should be corona in spots, with radio noise (like power
line insulators in damp and dirty conditions) which I did not observe.  But
is there some other type of test I could run which would differentiate
between the effects?

Gary Johnson
At 02:06 PM 04/03/2001 -0600, you wrote:
>Original poster: "Dr. Duncan Cadd by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>
>
>Hi Gary, Malcolm, All!
>
><snip>
>
>
>>> It is my guess that the
>>> wire coatings on these spools soak up water from the atmosphere,
>
><snip>
>
>>I once did exactly that in conditions of good isolation. The
>>resonator in question had a Q which measured 320 on a day when
>>humidity would have been about 10% and 300 on the following day when
>>humidity would have been around 80%+. Since R is inversely
>>proportional to Q that is an ESR change of less than 1%. I have found
>>that streamers from this coil do not propagate as far in higher
>>humidity and I attribute that to ionization phenomena.
>
>
>Could it be that any adsorbed water simply acts as a parallel leakage
>path to earth, i.e. shunt resistance?
>
>The insulation used on wires contains polar groups - in the case of
>polyurethanes and the like there's plenty of C=O groups which carry a
>permanent electric dipole.  Water molecules being themselves polarised
>would tend to stick to any polar layers on the insulation, simply
>being adsorbed onto the surface, and a surface layer of water
>molecules will provide a conductive leakage path for any charge "up
>top".
>
>If true, I would predict that coating the coil with a thin layer of
>something non-polar, like polythene, should reduce this problem.
>Unfortunately, applying such a coating is not going to be simple.  If
>you had high temperature insulation on the wire, you might be able to
>get the whole coil powder coated somewhere, but this involves cooking
>the whole thing to a couple of hundred C so you do need high grade
>insulation to start with, plus there will be a risk that during
>heating, turns will come loose en masse as the wire expands.
>Alternatively, you might get away with painting on a solution of
>polystyrene dissolved in a suitably volatile solvent, but this is
>going to be messy.  Likewise with molten paraffin wax.  Bit of a pain
>whichever way you go.  I have coated a couple of small coils with
>beeswax.  This was a bit messy, but as it melts at lowish temperatures
>it's really quite nice to do from a technical viewpoint - no loose
>turns of wire and no burned fingers.  Also, it smells good ;-)
>
>Just my 0,2 nanometres' worth.
>
>Dunckx
>
>
>