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RE: The Tabletop Tesla Coil Showdown - OFFICIAL RULES and WEBSITE
Original poster: "Dave Kyle by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-kyleusa-dot-com>
Franceformer Model 4020SE 4kV/20mA as seen on ebay
Austin, TX USA
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, September 30, 2002 10:01 PM
Subject: RE: The Tabletop Tesla Coil Showdown - OFFICIAL RULES and
Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
>From the referenced web page, comments proceeded by GL>
1. Must use a Franceformer Model 4020SE 4kV/20mA transformer. A
of 5 shunts (5 top / 5 bottom) must be installed and the maximum input
voltage may not exceed 125 VAC (RMS)
GL> 125V? Looks like I'll have to use a step-up variac so I'm not at a
disadvantage using only 115V ;-) For the shunts, I think the 5/5 rule
good as a general guideline, but particularly for folks using a similar
not identical 4/20 NST, I think the short circuit current needs a
maximum value. For my 4020SE, I use an 8/9 shunt configuration and I'm
sure I want to use any less for the well-being of my NST. That results
a 38mA short circuit current (-at-115VAC). For a 5/5 configuration, I'm
that would result in a significantly higher current, particularly at
125VAC. If this is a legitimate configuration, the SC current should be
specified as a maximum. It's an easy measurement to make. And perhaps
folks with an abnormally high 125V mains should be required to
to 115 rather than the reverse? Or would specifying a simple maximum
have the same net effect (not sure)?
GL> I propose these NST requirements, with a consistent
* Category 1 entries must be a Franceformer Model 4020SE 4kV/20mA
transformer, as above.
* Category 2 entries may be any 4kV NST with short circuit current not
exceeding whatever a 5/5 shunt configuration yields -at- 115VAC.
* Category 3 entries may use any NST whose rated open circuit voltage
short circuit current does not exceed the above VA rating. With higher
than 4kV NST, these will enjoy an inherent efficiency advantage over 4kV
users, but it will open the competition up to more people and it will be
instructive to see just how much can be achieved with the same VA.
Observers must simply interpret the results with this in mind.
2. Coil must be of a "conventional" type meaning the tank circuit can
be comprised of the NST, spark gap, capacitor, and primary coil.
Intermediate rectification and voltage multiplier circuits are not
permitted as are the use of additional transformers to step the voltage
This includes magnifier type designs.
GL> It's probably academic since folks are unlikely to bother with a
magnifier configuration on a table-top coil, but I don't see where that
would violate the underlying spirit of the competition - using the same
basic power supply without running it into the danger-zone. If adding
diodes, 3rd coils, or magic beans between the power supply and top load
improves performance without overstressing anything, then great! Of
greater concern is governing the gap. I KNOW that I can get better
performance if I open up my gap. I would propose setting a .050"
static gap to keep the field safe and level, except that this may hobble
category 3 entries using higher than a 4kV NST. Maybe just for category
1 & 2?
GL> Voltage multipliers and resonant charging schemes don't (I think?)
overstress the underlying NST, so these may be viewed as magic beans.
these are used and the modified NST VA rating is not exceeded, it should
fall into category 3.
3. Additional power may be used to provide power for rotary spark gaps,
blower gaps, etc... as long as is does not contribute to the input power
the primary or secondary.
4. The coil must be able to run for at least five minutes continuously
with no failure prior to making any streamer length measurement.
5. The spark gap may be of any type - static gap, rotary gap, blower
solid state gap, tube gap, etc....
GL> A rotary gap with a too-small mains-resonant cap will charge up to
more than 1.414 * 4kV, and this may be viewed as an unfair efficiency
advantage. I propose restricting the competition to static gaps in
category 1 & 2.
6. For the generic category, any 4kV transformer can be used except the
maximum output current must not exceed the measured output current as
measured using the modified Franceformer Model 4020SE above. Current
output must be measured prior to making any streamer measurements.
GL> I think verbiage is needed for measuring the output. Something
"Qualifying streamers (apologies to Bert) must connect to a grounded
at least twice within a chosen 60 second interval. One-time wonders do
qualify. Measurement shall be the straight-line distance from the
to the nearest point on the top load." Comments?
Regards, Gary Lau
>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
>I finally got around to putting on a page for the Tabletop Tesla Coil
>This is the official site where you'll find the rules, results,
>Will be updated daily.