Re: Capacitor in series with transformer or S.G ? What is right?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Harvey,

On 1 Feb 2002, at 19:49, Tesla list wrote:

> Original poster: "harvey norris by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <harvich-at-yahoo-dot-com>
> 
> 
> --- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "Gregory Hunter by way of Terry
> > Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>
> > 
> > Honestly, I don't think it makes much difference. I
> > prefer the spark gap across the transformer output,
> > with the tank cap in series, like this:
> > 
> > http://hot-streamer-dot-com/greg/basics.htm
> > 
> > The spark gap is more than just a switch--it is also
> > the master voltage limiter for the power supply, and
> > it may be more effective in this role if it is
> > directly across the power supply outputs. However, I
> > have used both gap/cap configurations with equal
> > success.
> > 
> > My $.02 worth.
> > 
> > Greg
> > http://hot-streamer-dot-com/greg
> > 
> The thing that I always had problem fathoming, is that
> when the arc gap fires, it then appears as a short to
> the power supply, yet at the same time this does not
> cause a great jump in (transformer primary)amperage
> input. The explanation given for the use of the rotary
> arc gap seems to make this comprehensible, because
> then the electrodes only come together for arcing when
> the source AC cycle goes to its zero point in the
> cycle, because the rotation of the arc gap electrodes
> is timed to the source frequency. If the gap fires at
> its AC zero crossing point, then a short at zero
> amperage input is of no consequence.

Actually it is. The reason fuses aren't fried in a typical Tesla 
system when the gap fires is ballasting or leakage inductance in the 
mains current path. A spark gap placed across the output of a 
transformer with coupling constant close to 1 would certainly see 
some "sparks fly", mainly from the fusebox.

Regards,
malcolm
 
> Thus the gap operated in static case must be modeling
> the same behavior? In one half cycle of source
> frequency, the cap must be fully charged,(if the 
> supply can meet the demand of current made by the
> capacitive reactance being used) The resistance of the
> arc gap is such then that when the cap is fully
> charged at the source frequency, it then discharges
> across that gap to produce the hf oscillation on the
> tank itself. But since the time for cap charging must
> occur during the half cycle of the input, by the time
> the discharge at gap occurs the source frequency must
> be coming close to its zero crossing point. Thus the
> arc gap already models what the rotary scheme
> manipulates,No?
> 
> Here is where another question comes up. Suppose we
> have a TC driven from a NST 15,000 volt 30 ma supply.
> By calculating the reactance of around 50 nf, we also
> find that is the ~value of capacity that would would
> allow that 30 ma conduction to occur. Doesnt this
> imply then that if we drive a TC with cap values above
> that 50  nf in its tank circuit,from this transformer
> NST , the source would not be meeting the demand?
> HDN
> 
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