RE: Random TC Questions- streamer current

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Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>

>it's also important to think about what fraction of the RF current
>is carried by the streamer (a small amount, I'd venture)

Whenever this comes up I always like to show this picture-

http://www.roffesoft.co.uk/tesla/dby2004/sc2004_0529_160408.jpg

This was an experiment done at the Derby Teslathon 2004 using my OLTC. We
connected the strike pole to ground via a 240 volt 30 watt filament bulb. Ie
it takes 125mA RMS to light fully. It lit more than fully- the filament was
melted in the first few seconds and the remaining bits of tungsten were
heated to a brilliant light by an arc passing through whatever gas was in
the bulb. Also notice the corona around the feet of the strike pole, it is
obviously taking a fairly high voltage to drive the arc through the bulb.

By way of comparison, the secondary base current of this coil is 8A peak and
(very roughly) 1A RMS.

So I take this to mean that a ground strike from a TC can potentially carry
quite a hefty current. As to what current is taken by streamers that don't
connect, you can estimate it by the ratio of streamer capacitance: topload
capacitance. Using Terry's rule of thumb of 1pF per foot, a 3 foot streamer
would take something like one-sixth of the total RF current. Whatever
measurements I have taken tend to come out with something nearer 2pF per
foot though.

I think this may underestimate the ratio too. Another thing I noticed at
this event was: When I ran up the coil with no breakout point the
fluorescent striplights on the ceiling all lit up. When I reached the
breakout voltage and a streamer formed, the lights went out even though the
power delivery to the coil had not fallen. That suggests the streamer is
pulling the topload voltage down.

Thanks to Derek Woodroffe for the picture.

Steve Conner