STRIKES INTO PRIMARY
Subject: STRIKES INTO PRIMARY
From: richard.quick-at-slug-dot-org (Richard Quick)
Date: Wed, 1 Mar 1995 00:59:00 GMT
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* Original msg to: Esondrmn-at-aol-dot-com
> From: Esondrmn-at-aol-dot-com
> Subject: Strikes into primary
ES> I did some more testing last night. Using one tank
ES> capacitor, tapped at 10 turns, as I turn the variac up I
ES> start getting strikes into the primary - apparently going
ES> past the strike rail.
I am trying to see this with my mind's eye. The problem is I
can't visualize exactly what "past the strike rail" means. I
assume you mean that the secondary discharge is striking the
primary coil at points that are inside of the strike rail
protection. With the strike rail positioned ABOVE the OUTSIDE
turn on the primary, how could the secondary strike the primary
coil at points that are "past the strike rail"?
ES> The discharges seem to be about equal leaving the top edge
ES> of the discharger and going up and leaving the bottom edge
ES> and going down.
You mean the top surface and the bottom surface: there should be
no "edges" on the toriod, it should be all smooth surfaces.
You need to make adjustments to the discharger system so that
secondary discharges are leaving laterally, not going up or down.
You can assit a small toriod that tends to strike the primary by
cutting out some one or two inch wide strips of leftover capa-
citor plate. Make the strips about four inches long. The strips
are then bent to form a gently curving arch. When set flat on a
table the arch should only be an inch or two high at the peak.
Affix the curved strip(s) to the outermost surface of the toriod
with some aluminum plumbers tape, if you imagine a toriod sliced
like a bagel, place the strip slightly above the slice line. The
protuberance of the strip(s) should be adjusted so that it
disrupts the toroid field just enough that the streamers will
favor the arched surface of the strip(s) and tend leave the
discharger sideways; not down to the primary. I always try to
adjust and shield things so that direct strikes to the primary
and tank circuit are avoided.
ES> When I use two capacitors in series and tap it at 14 turns,
ES> I can run it at full voltage without getting strikes into
ES> the primary or to the strike rail. Most of the discharges
ES> leave from the top edge of the discharger with this
When you use two capacitors in series and you tap out at 14 turns
the input energy into the system is smaller, and it is distrib-
uted over a larger area. This produces a field flux that is less
intense, and it is less likely to pull a streamer downwards into
ES> I have a theory: When it is tapped at 10 turns, the
ES> remaing turns of the primary act as an autotransformer.
ES> This would cause high voltage in turns 11, 12, 13 & 14. Is
ES> it possible that with one given swing of the 60 cycle line
ES> that these top few turns are more negative than the grounded
ES> strike rail? Thus attracting the discharge?
Well first off the primary/tank circuit is not a 60 cycle system;
it is a pulsed RF circuit. Secondly, I would tend to believe that
only resonant rise on the open end of a coil could account for
any voltage increase here, and this would be doubtful; the fre-
quency is too low and the coil too short for any significant rise
here. My guess, having done some experimentation in this area, is
that you are observing a magnetic field flux phenomena.
The Tesla tank circuit produces simply enormous peak powers.
When the spark gap fires the capacitor(s) discharge in an
oscillating pulse of short duration (highly damped wave train).
This pulse consists of dozens of amps at thousands of volts.
Even on a six inch coil system such as yours, peak powers of
several hundred killowatts are normal, and peak powers over a
megawatt are fairly easily obtained.
This peak power is transfered to the Tesla secondary by inductive
coupling. This means that hundreds of killowatts of energy are
changed into a magnetic field by the primary coil. This magnetic
energy is then transformed back into electrical energy by the
inductively coupled (magnetically linked) Tesla secondary.
I would submit that what happens is that the secondary discharge
is caught by the magnetic field flux, and is drawn to the source:
the primary coil. You said that the problem is exacerbated when
you run a single capacitor tapped at 10 turns, as opposed to two
caps in series tapped at 14 turns. This is important. When you
run two caps in series you reduce the tank circuit capacitance by
50%, which means a substantial reduction in your maximum
achievable peak power. When you tap at 14 turns with this reduced
peak power, the magnetic field produced at the primary coil will
be much less intense.
A single capacitor will deliver a much greater peak power than
two capacitors in series. A single capacitor will also require
fewer turns on the primary in order to maintain tune with the
resonate secondary. Thus additional capacitance has the effect of
creating a higher energy magnetic field (greater peak power) in a
smaller area (fewer primary turns). This field flux will have
significantly greater density and contain much higher energies.
What happens is that the field flux is then capable of coupling
to the discharger, and to the discharge itself. It then draws the
discharge to the energy source.
ES> When the discharges hit the primary it seems to be in turns
ES> 12, 13 & 14. It makes a real loud pop like a firecraker and
ES> sometimes the safety gap fires. What do you think?
I think you need to: lift your toriod up until corona or sparks
are detected in the upper most turns of the secondary, then drop
the toriod down just a smidgeon. Add some protuberances to direct
the sparks sideways and away from the primary. Then you can fire
while you work on your next toriod. When your larger toriod is
complete then repeat this paragraph until this problem is solved.
... If all else fails... Throw another megavolt across it!
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