RE: Odd coil behavior

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

In the good old days, coils had no coating, just cotton covered wire 
;-))  Then they were coated with varnishes or wax mostly since the cotton 
insulated like air against high voltage.  As the newer enamels came along, 
enameled wire was again pretty good but it was fragile.  So poly and 
glyptol coating came in again.

Most of us are not going to run at turn to turn voltage levels that will 
breakdown modern wire coatings*.  It could be argued that high power coils 
that get run a lot (like Jeff Parisse's and D.C. Cox's big pro coils) need 
added insulation due to their very hard use and need for extreme 
reliability (let alone all weather proof!!).  There is no ionization since 
all those air gaps do not glow blue :o))  If a coil has 1200 turns and has 
a peak voltage of 400kV, the turn to turn voltage is only ~~333 volts 
neglecting somewhat non-linear voltage rise.

Personally, my coils are not terribly voltage stressed turn to turn and I 
hate the mess, smell, and drying time of multi poly coats.  So I tried the 
stretch wrap and really like it.  It protects the coil very well and I have 
repaired some very bad damage caused by CW primary to secondary arcs (that 
would have destroyed a coated coil) very easily by just replacing the 
stretch wrap.  So stretch wrap may not be for everyone, but it is all "I" 
use now.

One should wind the wire very tight so it stays in place as the form 
expands and contracts some with temperature and humidity.  Or maybe just 
coat it with a light spray of poly from a can to grab the wire before the 
poly wrap.

So everyone will have to decide for them selves how they want to coat their 
coil (or even "if" at all...).  I just point out that stretch wrap provides 
excellent protection and is so super fast, cheap, and simple that you will 
have a hard time doing it any other way once you try it ;-))  Remember, 
that when I tried it, it had never been done before and nobody knew if it 
would work at all.  But is a very good way for many people to protect their 
coils from the trunk of the car and such and it is the most repairable of 
any methods.  Maybe it should be regarded as new and experimental, but the 
first experiments went very well!!  My big coil has its windings scraped 
bare every inch for experimentation and it still has no problem...

*I just wound two #24 wires together in about a 1 foot length at 2 twists 
per inch and stuck them on the small DC Bertan power supply...  Just plain 
Jane enameled motor wire as opposed to the fancy heavy build super poly 
space age stuff...  So what is the breakdown voltage?  300V, 500V,...1000V!!!

Hahaha!  Here it is easily holding off 10kV :-))

http://hot-streamer-dot-com/temp/Pa090030.jpg

I would have to hook up the big 50kV Bertan to really find out!!

Of course, this is DC.  AC should be worse.

Cheers,

         Terry


At 12:42 AM 10/9/2003, you wrote:
>I don't understand (but I'm new at this).  I thought the coating/wrapping
>was to insulate the windings from OUTSIDE elements, e.g., arcing from the
>toroid.  The plastic wrap should do this as well as a painted-on coating.
>Moisture in the air won't go through or get under the stretch wrap.
>
>I don't see how any coating will help inter-turn insulation if the winding
>is tight to begin with.
>
>Terry Fritz recommended the stretch wrap, and it sure was simple to put on;
>haven't had any arcing or racing sparks so far (knock on wood!).
>
>Dwight.
>
> > -----Original Message-----
> > From: Tesla list [mailto:tesla-at-pupman-dot-com]
> > Sent: Tuesday, October 07, 2003 8:29 PM
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Odd coil behavior
> >
> > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
>...snip...
> >
> > Someone on the list recently mentioned some type of plastic insulation
>that
> > could be easily pealed off later for re-coating.  This is terrible.  It
> > means that to an electron there is a space as large as the grand canyon
> > between the wires enamel insulation and the polymer coating he used.  The
> > overall effect is that the coating he used wasn't contributing anything of
> > value with regard to insulating the magnet wire.  In fact, it might only
> > contribute to capturing atmospheric moisture.
>...snip