Re: Big x-ray transformers and Jacobs Ladders.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "david baehr" <dfb25@xxxxxxxxxxx>


yes, id say more VA  will make a longer arc,....higher voltage would 
give you a greater 'starting' width at the bottom, but after that  VA 
rules,.......HECK, I DONT KNOW !!!





From:  "Tesla list" <tesla@xxxxxxxxxx>
To:  tesla@xxxxxxxxxx
Subject:  Re: Big x-ray transformers and Jacobs Ladders.
Date:  Mon, 23 Apr 2007 13:26:21 -0600
>Original poster: FIFTYGUY@xxxxxxx
>
>In a message dated 4/22/07 11:59:05 P.M. Eastern Daylight Time,
>tesla@xxxxxxxxxx writes:
> >It's my understanding that the arc length of a JL
> >is primarily dependent upon the current
> >available, not the voltage.
>
>     It's my experience that the maximum arc length of a JL is
>primarily dependent on the *Volt-Amps* available. At least under the
>typical conditions of continuous sine wave low frequency AC power
>sources.
>
> > Once the arc is established, the voltage drop across it is only a
> >few hundred volts, if that much. Supplying it
> >with more voltage doesn't do anything to increase
> >the arc length.
>
>     Well, the rising of the arc tends to lengthen it, and it will
>take more voltage to sustain the longer arc.
>
> >Other list members have reported
> >that X-Ray transformers have made disappointing
> >JLs, because they can supply relatively little current.
>
>         Who reported that? I haven't found anything like that in
>the archives.
>
>         I've got both a 10kVA 14.4kV pole pig (from Resonance
>Research) and a ~125kVP 300mA XRT from Jack King.
>
>         First a word on my ballast: I made a core out of pieces I
>cut out of an old 25kVA SCR Drive Isolation Transformer. Much
>cutting and cursing later, I had an open "E" core with a pretty big
>area (I can measure if you really care). I wound the middle leg with
>four parallel 12 ga THHN wire (IIRC it was true bifiliar, with
>interspersed reverse-parallel pairs). Everything is nice and cool
>after 5 minutes of running, and with no closing "I" the open core
>limits short-circuit current to 60 amps.
>
>         Now for my pole pig's JL performance, which I believe I
>mentioned here before:
>
>        Arc starts at typical ~1/2" electrode spacing, and will
>climb until the point at which the electrodes are ~18" apart.
>Doesn't seem to matter much whether the electrodes are a steep 90
>degree "horn" gap or a gentle 6' tall JL with the bottom 2/3 in a 6"
>diameter Pyrex tube.
>         Now the interesting thing: My pig has a switch on the side
>to convert it to 7.2kV operation - half the voltage at twice the
>current. A little tougher to start the arc, and less reliable to
>keep it going, but mostly it looks the same! Same maximum arc span,
>too.
>
>         My XRT performance:
>
>         I had to build another JL base for the XRT (yes, the pole
>pig runs this JL the same way it ran the first one...). After all,
>the XRT will *start* an arc with the electrodes maybe 12" apart! And
>sometimes the arc just wants to hang out at the bottom, writhing
>along the base, instead of climbing! The solution to that was to
>almost "bridge" the electrodes about halfway up with extra "starter"
>points - two 10" pieces of copper tubing hose, one clamped to each
>electrode. The "starter" pieces each point down and into the JL's
>"V", and have their points ~8" apart. Thus the arc starts at them,
>2' away from the support base for the JL . Even then, it sometimes
>doesn't want to climb. Max arc span is perhaps 24".
>
>         Now, I think if I could enclose the XRT's JL then it might
>do a bit better, maybe 36". But since the current *in* to the XRT is
>limited to 60 Amps, it can't sustain much current once the arc is
>started, and thus doesn't do as well as you might expect. After all,
>the rated current in is more than twice that. I think it could be
>pushed harder for a few minutes. Nominal output is 89kV AC, at
>300mA. Obviously it's starting the arc at that high voltage, but it
>can't deliver that voltage at that current to sustain the arc enough
>to make a significant improvement over the Pole Pig's efforts.
>
>         So over-running my Pole Pig by 50% is a little less
>impressive than under-running my X-Ray Transformer at about 40%. I
>suspect running each at their rated output would reveal a big
>difference ion performance.
>
>         I've got a little XRT I've never run that would make a
>useful comparison, were it not for the fact that it runs at 8kHz.
>That also means I'd have to build an 8kHz 110V 100 Amp  power supply
>for it, which would be non-trivial (maybe a car alternator?).
>
>         While I'm writing about it, I've noticed that sometimes the
>JL arc from my XRT "snaps" loudly. I've chalked this up to cable
>capacitance (I'm using two 15 foot lengths of X-Ray cable to plug
>into the wells, stripped ends to the JL). Sure sounds like a safety
>gap firing when it does this! Yes, the rectifiers and filament
>x-formers are removed, and the milliameter connection is shunted.
>
>-Phil LaBudde
>
>
>
>
>----------
>See what's free at
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>
>



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