Re: Secondary Turn Spacing

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Cameron,

First of all, I hope everyone has had a great Vateran's Day and will
remember our troops that are in harms way even as we now speak.
Now on to Cameron's question. It seems that there are varying opin-
ions regarding this. Some will really "sweat" the distrubuted capaci-
tances noting that every turn of wire forms a "little capacitor" with its
adjacent turns. Others will state that these unwanted distributed capa-
citances are offset by the obtainable lower aspect ratio along with the
higher secondary inductance of a non-space wound secondary coil.
I've tried it both ways and to be honest, "I"
couldn't tell a nickel's worth of difference in the output of the finished
coils between spaced or non-spaced secondary coils. Of course I
don't have all of the fancy scopes, freq counters, signal generators,
ect. to really look into this like some fellow list members do. All I
am going on is the final obtainable output spark length. I do know that
winding a non-spaced secondary is considerably easier than winding a
spaced one so I wind all of mine "non-spaced" now. Also, there may
be a latent moisture issue to deal with using nylon fishing line as I've
heard that nylon is somewhat agroscopic and will retain some unwanted
moisture, especially in humid climate conditions. I've never really noticed
that either though with my "space wound" secondary coils of the past and
I reside in Memphis, TN, which has plenty of humidity, especially during
the summer months. To me, it seems to boil down to balancing the "bad"
distributed capacitances of a non-space wound or "closewound" secon-
dary coil against the "bad" lower inductance and higher aspect ratio and
larger coil volume of a spaced wound secondary coil. Otherwise to keep
the aspect ratio lower and the inductance per secondary coil volume high-
er with a space wound coil, you must use a smaller guage of wire to accom-
plish this but smaller guage (smaller diameter) wire increases the DC resis-
tance of the secondary coil. This isn't as much of an issue with smaller
NST driven systems but does become an issue with 15 kVA pig driven
systems. I'm sure other more knowledgable list members can offer more
insight into this issue but this has been my observations regarding this.
YMMV.

David Rieben

-- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, May 30, 2005 5:54 PM
Subject: Secondary Turn Spacing


> Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>
>
> Hey guys,
>
> I'm getting ready to wind a new secondary and I wanted to get your input
> turn spacing. The coil will be wound on a 12" diameter PVC form and I will
> be using #17 AWG enamel coated solid wire. The coil will be driven by a 15KW
> pole pig @ 14,400V. The topload will be a 10" x 30" spun aluminum toroid.
>
> I was considering using 17lb. test nylon fishing line to space the turns in
> an effort to minimize distributed capacity.
>
> Could you guys give me your opinions on this?
>
> Thanks,
> Cameron