Arc/Spark RE: [TCML] Magnetic Quenching
electrotherapy at hotmail.com
Fri Sep 12 14:56:51 MDT 2008
My point here is that if an "arc" can be interrupted (at 100kW or more, or 1 kW for that matter) by a magnetic field, then surely there are possibilities for this type of setup with a spark gap in a Tesla Coil. There were many articles and references to such things using nothing more than simple electromagnets, and with the strong permanent magnets available today this would seem even more practical. I know off hand the Cunningham book on Tesla coils give plans for a simple spark gap of this type, and I think I have a book by Winfield Secor that gives a variation of it too. It was always said that the magnetic field would prevent "arcing" in the spark gap if high currents were used.
Tesla heavily criticised Poulsen arcs as merely variations of some of his early spark gaps, both the aspects of a non-oxygen environment and the magnetic field - both were mentioned in his early lectures. There are distinct pictures of an "arc" gap inside of a chimney, where a lamp or flame is present below the gap to rid the container of oxygen, and the dischargers are mounted in bearings with springs so that they could be pushed inward to short temporarily and start the "arc". This was granted "crude" in comparisson to Poulsen, but for our purposes might be useful, as Tesla was of course using this for Tesla Coil operation...
While the operating characteristics are definately different, the circuits are essentially the same, at least on the surface - some inductance in the form of choke coils or "kicking coils", inductance in the form of a high frequency coil, capacitance, and a spark gap/interrupter or "arc gap". Apples and oranges, but still fruit.
A kicking coil operates well with low currents only because the interrupter limitations, mercury interrupters are expensive and complicated - but what if we replace the interrupter with an "arc" gap? Mechanically more complicated, but simpler than mercury. I read somewhere that some of the singing arcs operated at around 50kHz. That sounds pretty useful! Where can we get one!?!? :)
Likewise, what if we make something that will more easily quench a single gap for a MOT transformer, 2kV at 500mA - 1000mA or more... This would be great fun for Pancake Coils and smaller table top coils. I know from making complicated tungsten gaps to accomodate these circuits that the sparks are spectacular in the output of the coil if you can get around the obstacles of the high currents in the tank. Magnetic quenched gaps might be a solution, espescially for people without a complicated machine shop at their disposal. (I take this granted some times, and don't really mean to...not everyone fills their house with metal filings to accomodate their hobby, sorry folks...)
A long time ago on and off the list, I remember "Bill The Arcstarter" and I were taking to a man who actually built a Tesla coil powered by a Poulsen Arc. I unfortunately lost the paperwork he sent, but maybe Bill is still around and has copies of this? It was a brilliant feat, as he was probably the only person alive to ever make an operational Poulsen arc, much less use it to power a TC!
I don't know if that man is still alive. I can check my emails, but I have a bad feeling they were from too long ago and I doubt they still exist...
> Near as i can tell:
> utterly different.
> In engineering a _spark_ is quite distinct from an _arc_.
> An arc oscillator is (noisy) CW, a spark gap provides damped
> waves. An arc (in operating range) has negative resistance,
> this allows gain, which allows oscillation: CW oscillation.
> With respect, the usage of the terms 'arc' and 'spark' in
> Tesla Coil discussions is rather too lose.
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