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

[Gary Lau <glau1024@xxxxxxxxx>]

In my experience, Bigger is always Better when it comes to secondary size
and toroids.  I would say that 6" for the secondary is an absolute minimum
if getting the maximum performance is the goal.  A 24" toroid is,
unfortunately, rather on the small side for that power level.  For my single
15/60 & SRSG, I use a 7x30 toroid.  For a 6" secondary, the #27 wire is OK;
I'd go with the #24 if using something larger.  Basically, you want to shoot
for a 5:1 aspect ratio and 1000-1600 turns, though there's a lot of wiggle
room here.

While there's no doubt that an SRSG will perform far better than a static
sucker gap, just understand that if you start out using the static gap,
converting to an SRSG will require a complete overhaul, as the cap size has
to increase significantly, and that will affect the primary design, and
secondary geometry.  When using an SRSG, a cap size less than LTR is simply
not an option, and needs to be roughly 3X the mains-resonant value, or else
the safety gaps won't stop firing.  You really need to decide in advance
what type of gap you want before doing anything else, including designing
the cap and secondary.  Building an SRSG is not something one can throw
together quickly.  If you're in a hurry, better start with a sucker gap and
plan to re-do everything some day in the future.

Regards, Gary Lau
MA, USA



On Thu, Jan 20, 2011 at 3:35 PM, Mark Crowley <maccrowley8965@xxxxxxxxx>wrote:

> 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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