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Re: Trigger the capacitors
Gary Weaver wrote:
> Can anyone think of a way to use a tesla coil to trigger a discharge from a
> capacitor bank with out distroying the tesla coil?
>
> A zenon flash tube is attached to a cap and the cap is charged but will not
> discharge threw the flash tube until a high voltage is used to triger the
> flash tube.
>
> What I would like to do if I can think of a way to do it is to discharge a
> capacator bank threw a high voltage arc from the tesla coil to simulate a
> small lighting strike.
>
> I have 6 capacitors connected in parallel. All 6 capacitors are 210 uf 5000
> VDC 18,000. amps high energy storage capacitors. With all 6 connected in
> parallel I get 108,000 amps at 5000 volts DC. The discharge from this is
> unbelievable. The arc is about 1" long. Sounds like a stick of dynamite. The
> flash is so bright it is blinding. It will vaporize 6 feet of 1/8" solid
> steel wire. It vaporized a 5000 watt flash tube I got from the air port.
>
> How can I discharge this capacitor bank threw a long high voltage arc.
>
> I am not sure it can be done. If so I have not thought of how to do it yet.
>
> Gary Weaver
The easiest way by far to discharge into a TC streamer is to allow the cap bank
to discharge thru the secondary of the tesla coil. The reactance of the
secondary, however, will limit the peak cap discharge current, and I understand
that you are trying to optimize the peak arc current.
Your experiment with the steel wire is probably the best way to generate a
lightning-grade flash. The igniting wire can be hair-thin; I use a 0.008" dia
nickel alloy wire. Your capacitors should be placed in series for optimum
striking length; a minimum of 2500 volts per foot of wire is required to fully
develop the lightning strike along the wire. I have discovered that this
'magic' 2500 volts per foot value is quite constant for distances up to at
least 50 ft, and probably much further. 2400 v/ft usually results in a wire
fizzle (99% of bank energy intact) and 2600 v/ft usually insures a solid
arc (99% of bank energy comsumed). The threshold is amazingly sharp.
You should be able to reliably generate an air discharge of 10 ft with your
cap bank configured for 30kV operation.
At the present time I use a pneumatic dart gun, where the nickel wire spools
off of the dart as it flies from the gun (HV terminal) to a grounded target.
The gun, which has 30 barrels to allow multiple shots between loads, sits on top
of a 110kV Marx generator, with a total C of 14uF. Upon impact, the dart completes
the circuit and triggers the gaps in the bank, initiating a disruptive discharge
thru a plasma channel in the air that is seeded by the wire. The max. arc length
observed to date is 47 ft, with a peak current of 14kA measured at the target.
The brissance of the explosion is such that I usually get a bad sinus headache,
and an odd sensation of nausea after about 5 successful shots. I no longer look
directly at the flash, as it will leave an retinal image for a minute or two --
even thru #5 welding goggles.
Recently, an organization donated to us several palletes of high energy storage
capacitors -- 400uF, 6kV, 41 units total. We are currently designing a new
Marx bank that will employ 36 of these capacitors in series for 216kV service,
in order to increase the striking range to about 80 ft. Hope to be done with
it by the summer.
By the way, does anyone out there have a line on fiberglass pultrusion stock,
such as 2x2 or 2x4 sq tubing? The stuff's expensive!
-GL