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RE: First light for an old coiler



Original poster: "Dave Kyle by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-kyleusa-dot-com>

Hi John,

Thank you for the reply. I checked Bart's JavaScript Tesla Coil Designer
http://www.classictesla-dot-com/java/javatc.htmland with my parameters it
suggested the Transformer Resonant Capacitor was .016 uf. Is that wrong? I
thought I was operating in a fairly safe LTR zone. Here are my current
specifications:

20 amp Variac
15 KV at 90 ma (3 x 15 KV at 30 ma Transco transformers)
140 uf PFC capacitors (4 x 35 uf at 330 VAC)
Standard "Terry" neon protection circuit (RC with grounded safety gap - less
MOVs)
1800 RPM SRSG using four .095 inch Thoriated Tungsten electrodes with a
static gap in parallel
.03 uf at 70 KVDC (4 x .03 uf at 35 KVDC Maxwells, 2 in series and than
paralleled)
15 turns .25 copper tubing primary currently taped at turn 10
6.25 inch PVC with 36 inches of #22 wire secondary
24 inch spun aluminum toroid

I did some tuning work today and after some re-phasing of the SRSG the
arcing at the static gap ceased. I had already reduced the static gap to
about 3/4. I was about to adjust the primary tap when the Variac fuse blew
for reasons as yet unknown and ended today's fun. This is a rather
inexpensive KRM Variac and I think the fuse itself failed but I will not
know until tomorrow when I pick up some new fuses. I am still at about 21
inch arcs but I never got a full power run and I suspect the primary
adjustment will be significant.

I am using your excellent phase adjustment circuit on my SRSG although I was
only able to get about 20 degrees of range without the motor severely
vibrating (mine is an unmodified commercial synchronous motor). Still my
rotor design makes it very easy for me to manually adjust the rotor position
while powered down so the 20 degrees provides plenty of fine tuning room
once I get dialed in. It was very interesting varying phase while the coil
was running as it dramatically impacted the arc length as well as when the
static gap would cut in.

Best regards,
Dave



=========================================
Dave Kyle
Austin, TX USA
Email: dave-at-kyleusa-dot-com

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, November 14, 2001 1:06 PM
To: tesla-at-pupman-dot-com
Subject: Re: First light for an old coiler


Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>

In a message dated 11/14/01 9:50:10 AM Eastern Standard Time,
tesla-at-pupman-dot-com writes:

Dave,

You're using a resonant sized capacitor, so you have to be
very careful.  Your safety gap at 1" is kind of wide.  Folks
will tell you the static gap should be set at the distance it
will fire with nothing else connected to the NST.  However,
such an adjustment will severely limit your spark length when
using a resonant value cap.  To get the max spark length
from a resonant coil with the SRSG, you'll need to use a
rather wide safety gap setting of at least 7/8", despite the
danger to the NST that that represents.  This is why the use
of an LTR value cap is recommended.  In any case, first of all,
the total gap spacing at the SRSG should be set very narrow,
at about 1/16" or less.  Otherwise, the combination of the wide
static gap setting, and the wide SRSG spacing will quickly
destroy the NST's.  It's very easy for the SRSG to fail to fire;
it needs a narrow gap spacing.  It's important to phase up the system
at low power, and never run it out of phase at high power.
When all is set correctly, the safety gap should *never* fire.

It's much safer for the NSTs to use an LTR cap of at least
double the capacitance value you're using.  I used to use
a resonant cap with a sync gap, and I had no problems, but
some other folks did.

Your coil should be capable of rather long sparks of at least
7 or 8 feet.

Cheers,
John
-

> Follow up to my previous posting. As you may recall from my earlier post
the
>  16 inch high test secondary was severely over-coupled leading to serious
>  dancing arcs across the surface of the secondary. Happily the 36 inch
>  secondary coil in exactly the same configuration shows none of this
>  behavior. With no tuning or adjustment I achieved 21 inch arcs to a
grounded
>  object and 12 inch breakout was seen on the toroid. I am hoping to double
>  this with tuning and higher power settings.