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Re: Interesting Effects

Tesla List wrote:
> 
> Original Poster: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net>
> 
> Hello All,
> 
> 
> Playing around with my 8" coil I have noticed something interesting
> (probably been seen before and commented on) and would like to hear some
> comments on it. My main gap is set so that I do not need the full power
> setting on my variac. The spark gap will start to fire somewhere around the
> 80%  (Variac is a 0-250V model) setting. After the gap begins to conduct I
> can reduce input voltage (to about 60% on the variac). This doesn&acute;t
> come as a surprise to me, but I have noticed the following:
> 
> a.) Reducing the input voltage until the gap is on the ragged edge of
> conduction, will get me less streamers, but they are a lot longer and very
> lazy.
> 
> b.) Going higher than the 60-65% (to about 80% meaning ~220V) setting gets
> me shorter streamers, but more of them. Their speed doesn&acute;t change
> much, tho.
> 
> c.) "Overvolting" the NSTs (they are designed for 220V, and I am "giving"
> them 255V. They do NOT saturate at this voltage, I have checked this)
> doesn&acute;t get me any more streamers and does not change their length.
> However, they start swirling around the toroid like crazy (about once
> around every second or two).
> 
> Now, this is a surprise to me. I figure that at the 60% setting I must have
> the lowest BPS rate, while at the other end of the scale (255V) I must have
> the highest BPS rate. The noise that the spark gap makes would support this
> theory. (More power in = faster recharge rate). >From what I have heard
> (haven&acute;t built my RSG yet) going up in BPS rate will get you longer
> sparks (otherwise why would coilers do this?).
> 
> Before I forget: I am using a 7.5kV NST with 75mA and a 25.5nF cap. The
> 25nf cap is about 80% of the capacitance necessary for resonant charging.
> The results (a thru c), however, will work with any cap value I have used
> so far (9,10,12,15,20nf). I did retune the priamary for every cap used. Of
> course, the more capacitance used, the longer the sparks get, but the
> effects are the same.
> 
> WHY?!?!?
> 
> Coiler greets from germany,
> Reinhard
> 
> 

	I have noticed similar effects here.  With a capacitance that close to
resonance you will still see a significant voltage rise when the
transformer is unloaded (i.e. before the gap breaks down).  Furthermore,
because of changes in core permeability witgh flux level, the leakage
reactance of the transformer is probably significantly higher (placing
the system closer to resonance or in resonance) with lower primary
voltage. I have actually seen the case where, at an input of about 20
volts, the system "went series resonant" with a sudden huge increase in
output voltage.  Under conditions like this, it is possible to get
chaotic behavior with very erratic firing of the gap.  I would suspect
you are seeing some such condition where, at lower primary voltage, the
firing voltage of the gap increases with resultant long single
streamers.

	If everything were linear, increasing the input voltage would increase
the firing rate accordingly, once the gap breakdown voltage was
exceeded, in agreement with what you report.

	Sure there will be some more coherent answers to your question.

Ed