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Re: [TCML] Alternate to a spark gap


Won't work -- defeats the whole purpose of the TC system.

The firing of a TC represents the breakdown of the spark gap, turning it from a near perfect insulator to a low resistance plasma channel that hooks up your capacitor (which has just been charged to a high voltage by the NST) in series with the primary coil. The stored energy in the capacitor / primary coil circuit sloshes back and forth at something between 50 and 250 Kilohertz, a frequency ~1000 times higher than the primary 60 Hz current in your NST, passing through the spark gap, which is pretty much a short circuit at that point.

The really high speed transfer of the energy in the primary circuit to the L/C circuit of the secondary / toroid combo is what transfers the energy to make the TC discharge. You charge the circuit slowly, over ~1/60th of a second, but dump it out in a handful of microseconds.

The breakdown event is all done and over with in a very tiny fraction of the period of the 60 Hz waveform that charged the primary cap. During the ringdown, the NST is an innocent bystander, and contributes essentially nothing to the discharge.

What you are suggesting is roughly along the lines of the more modern SSTCs or DRSSTCs. In these systems, the semiconductors actively control the primary current without needing a spark cap.


On 8/18/2010 8:06 PM, Brian Hall wrote:
I noticed that one of the loudest parts of a spark gap coil is the spark gap itself.

So, could I just turn my 15/30 NST on and off rapidly through a 555 driving a mosfet or power transistor (than can handle house current, or even dialed down a bit through a variac) ?  Would it do any harm to the primary of the NST, being on and off that way?  As its usually the secondary alternating rapidly through th SG...

and by the way I happened to notices they have mosfets at radioshack in the parts drawer now for about 2 bucks

Brian Hall
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