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Re: [TCML] Best design for a 15KV 120mA trans?



Hi Mark,

Welcome aboard. :^)

You seem to already have a pretty good understanding
of most of the "rules of thumb" for SG driven coil TC de-
sign. For a 15/120 NST driven system, I would suggest
a 6" diameter secondary coil and keeping within the 4 to
5 range for an aspect ratio should keep your secondary
coil's length in the 25" to 30" range. You could even go
with an 8" dia. and a 35" to 40" coil length if you felt so
inclined. Most would also agree with a toroid major dia-
meter that is near the same measurement as the secondary
coil's length, so you 24" diameter  toroid (major diameter,
I'm assuming) should fit the bill nicely, assuming a choice of
a 6" diameter secondary. I'm assuming that your toroid's mi-
nor diameter is something "sensable", like in the 4" to 6" range?

Also, for an NST system, I would strongly suggest going
LTR cap size with a SRSG to get the most "spark for your
watts" ;^) NSTs tend to be fragile to the transient kick
back surges generated by the primary circuit and the LTR
primary cap size helps to clamp down the runaway resonant
voltage rise, which is a lot more healthy for your transformer(s)
and capacitors. Many NST coilers also opt for the Terry filter
as additional precaution  against the runaway Res. voltage rise
in the primary circuit just incase you open your gap to wide
or have a misfire.

JAVATC is about the best program out there for designing
your coil on paper before going forward with procuring actual
parts to start building.

Good luck,
David



----- Original Message ----- From: "Mark Crowley" <maccrowley8965@xxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, January 20, 2011 2:35 PM
Subject: [TCML] Best design for a 15KV 120mA trans?


Hello all,

My first post and my first question!

I recently came into possession of (2) 15 KV non-gfi neon sign transformers
@ 60 mA each.  I plan to parallel these two together for 120 mA total to
feed a large coil.  Although not my first Tesla Coil, it is by far the
largest I have undertaken.

My question is what would be the optimal secondary size for this?  I've
searched the archives here and it looks like 6" to 10" diameter seems to be
preferred but have also heard 4.5 Inch diameter coils driven as well.  A
height to diameter ratio of 4.5:1 seems to be recommended too.   I already
have two large spools of 27 AWG and 24 AWG high temp wire available so I
would like to use those if possible.  I have not purchased the sec form
yet.  (I also have a 24 inch diameter toroid available).  I have a large
collection of the CD 0.15uF MMC on hand and leaning towards LTR cap with a
sucker gap or a SRSG  (I've been hoarding parts for both :-) )

I've experimented with JAVATC and now at the point were I need a push in the
right direction for the secondary/wire size and number of turns.  Any
advice?  LTR cap good or go under LTR for this size?

Thanks again,

Mark
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