Re: First Power Up Test

Tesla List wrote:
> >From ccurran-at-execpc-dot-comWed Jul 31 21:42:01 1996
> Date: Wed, 31 Jul 1996 08:39:49 -0500
> From: Chuck Curran <ccurran-at-execpc-dot-com>
> To: Tesla List <tesla-at-poodle.pupman-dot-com>
> Subject: First Power Up Test
> Hello Group:
>         Well, last night I was able to get enough time to set up and accomplish
> my first test firing of my new coil.  It immediately shot out a 20"
> spark from the toroid to my "test ground" which was simply a chunk of
> #14 wire going from my earth ground to a point within 20" of the
> toroid.  This spark was very thin and blue, but the multiple arcs from
> the outer primary turn to the strike rail mounted about 1 3/4" above the
> outer primary turn were wide and white--there seemed to be 3-4 firing
> almost at the same time.  Apparently my next step will be to get the
> primary and secondary resonant frequencies closer together!  My
> secondary with the toroid resonates at 140 Khz so I then picked a tap
> point to give a primary resonance at 130 Khz to compensate for the
> charge build-up on the toroid which I understand typically drrops the
> secondary resonance point.  My toroid is 48" in diameter using 6"
> aluminum flexible duct as the outer ring.  I had seen up to about 220
> volts going in and 4.5 amps and it was sparking--I stopped watching the
> panel then and just watched the primary arcs!! Any opinions on whether I
> should move my tap to a lower frequency first?  Since I am asking a
> question here I'd better list some system specs too:
> Power Supply: 14,400 VAC 10KVA pole pig limited with a Century Arc
> Welder (set a minimum settings for first test)
> Spark Gap: seven gap 1 1/2" dia. copper tube sytem with fan, in series
> with a  rotary--12 breaks/rev running slow--maybe 1500-2500 RPM???
> Primary:  14 turns of 1/2" copper with 1/2" gap between turns.  About
> 11" I.D. and 40" O.D.------Tapped at 9 3/4 turns.  Condenser Products
> .025 Mfd cap at 20,000 volts same as many in the group.
> Secondary:  8" dia, acrylic form with 28" of #20 wire using a 48" dia.
> toroid.
> I figure if anyone could suggest going up or down in my primary
> resonance point it might save me some time and possibly reduce the risk
> of lots of generating lots of smoke!!  I already have apparently blown
> the free digital volt meter I got!  Tonight I hope to try again so any
> comments about your past efforts and knowledge would be appreciated.
> Thanks
> Chuck Curran


Congratulations on First Light!! 

I suggest the very FIRST thing you should do is to increase the 
seperation between your strike rail and the outermost primary turn so 
that you no longer get high current flashovers between the primary and 
the strike-rail.  Since you are presently at turn 9.75, autotransformer 
action is stepping up the voltage on the remaining turns, so that the 
outermost turn is running at > 1.5X your peak primary tank voltage. This 
added "kick" will ZAP(!) your primary cap and any other susceptible 
element that may find itself in the resulting high current/high voltage 
path. Even your safety gap may not protect you in this situation. This 
must be corrected immediately. A more involved fix would be to remove 
some of the innermost primary turns so that you are closer in tune when 
tapped at a point further out on the primary. Problems with high peak 
voltages on the outermost turns are common when actively only a portion 
of the primary in the tank circuit. Imagine the voltages that would be 
present if you dropped down to using only three turns! 

Now to your qyestion: 
Since you're starting out at relatively low power, I'd suggest initially 
matching the tune of the primary and secondary. You won't go wrong at 
this setting, even at high power. Once you increase the power level, you 
can experiment with a little more primary inductance to see if this 
improves performance. I'd be surprised if you needed to add much more 
than 1/4 Turn (about 4 kHz). 

It sounds like you have the makings of a hot system!! Good luck, and safe 
coilin' to ya!

-- Bert --