[TCML] Rectifying A Tesla Coil: Point-Plane Collector
electrotherapy at hotmail.com
Thu Sep 4 16:31:16 MDT 2008
The information you posted below is wonderful!
A comment/question concerning this great paragraph:
> In a positive discharge (where the discharge begins propagating from the
> more anode to the cathode), the leading edge of the propagating positive
> leader, and the leader channel that connects back to the anode, are
> bright and filamentary/spark-like. However, the streamer region ahead of
> the leader tip is diffuse, dimmer region that looks like a directed cone
> of corona pointing towards the cathode. If the HV source does not have
> sufficient energy to completely bridge the gap, or if the HV pulse is of
> very short duration, you get a miniature Tesla Coil-like air discharge:
> a bright length of spark that only goes part way across the gap, with a
> diffuse glow between the sharply defined leader tip and the cathode
First off, one thing you mentioned in that post hits the nail right on the head for what I'm seeing here most of the time, and "how" I'm seeing it.
Low power levels seem critical as you mention, and a spark gap with capacity (6" plates or even a normal spark gap
with a .001 condenser in parallel with it...) - gap set just at the very maximum distance, the capacity seems to help this to happen - whether its mechanically
part of the gap or externally with a small cap in parallel - the discharges do speak volumes, but in my case I don't know what language they're speaking! Luckily you are a good translator!
In the case of "Phantom Streamers", which closely resemble Negative discharges in Static Machines,
I noticed a few things about them, maybe you can elaborate...
They seem to appear in some coils at the ends of sparks generated from the topload - I've seen as an example
branching positive-like sparks a foot long where the conical diffusion will extend from the very tips of the branches outward - sometimes from
a needle thin portion out to a cone 6" or 8" in diameter or more at the base. Its a fascinating display to say the least.
(As an example, I think for 100 watts of power one tank circuit used a .2 mfd cap, a simple 6" diameter spark gap with 1.25" diameter tungsten faces, gap set to discharge once or twice a second, approx 1000 volt transformer, with a 5" diameter cylindrical Tesla Coil normally giving sparks 3-4 feet long at full power)
In the case of other coils though, I've seen them with nearly the opposite conditions - high voltage tank circuits charging small caps and
discharging across gaps only the fraction of the maximum voltage - for example, a single Pancake Coil, 9" diameter, as little as 200 turns of wire, 10kV OBIT, .01 mfd cap, 1/8" diameter 2 or 3 series spark gap (total gap less than .06") In this case, the 2" ball terminal of the coil showed no "roots" or sparking to speak of, but phantoms nearly 12" long - the same "diffused" phenomenon of the above coil, but diffusing in all directions from the same sphere, 360 degrees...it would produce a 2-3" spark if you brought a metal rod to the ball, but little to any brush or other sparking effects without some external influence approaching. Even with a metal rod drawing sparks, the phantoms still persist in all directions regardless...
Now, in the later case changing the condenser capacity has little effect in the appearance of the "phantoms". Likely because the cap value is small? In the former case, changing the capacity would make the "phantoms" start to have some shape, maybe slight branching or wavy-ness, where before they were pretty much straight faint lines...?
Also, in both cases, the phantoms appear to strobe inward or outward. At first sight I thought they were stobing outward, but it seems to make more sense that they could be strobing inward toward the terminals from the outside air...the cathode representing the free space around, as opposed to an actual metal terminal? Maybe its as if there was a positive spark barely visible at the terminal, or simply not discharging from the terminal, and the negative diffusion is the only thing seen, ocurring to a much greater extent, maybe 85% of the visible discharge?
A further question, the length of the Phantom streamers seen, and the presence of them felt is much different. If you can see a phantom streamer for 6 - 12", you may feel strong electro-static effects present by them at a distance of 12" to even 2 feet or more when the conditions are right. The hair on your arm will vibrate up and down at a similar rate that you see them strobing... the effect is much stronger when you place your hand directly in the visible portion, but there is definately a very real portion not visible, or maybe too faint to see...? I live in high humidity, it would really curious to try this somewhere in a dry climate...
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