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Re: SPDT SRSG
Steve and Terry,
I think that one of the earlier pioneer coilers (Mark Barton?) tried
this approach some years ago with a pole pig. The resulting kickbacks
were of such magnitude that they overvoltaged and popped filaments in
light bulbs in his neighbor's house (fed from the same utility
distribution transformer). The neighbor was not amused... :^)
However, it may be that the higher leakage inductance of an NST may make
similar gap misfires less "interesting".
-- Bert --
Tesla List wrote:
>
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
> At 12:56 PM 01/01/2000 -0700, Steve Young wrote:
>
> >
> > Hello list,
> >
> > Another scientific curiosity question: Has anyone experimented with a sync
> > RSG designed in a SPDT configuration? By that I mean the cap is
connected to
> > the center pole of the gap-"switch". The pig (or other HV transformer)
> > connects to one pole, and the TC primary connects to the other pole. There
> > would thus be two gap presentations per bang. The first presentation only
> > charges the cap. The second presentation discharges the cap into the
primary
> > tank, completely isolated from the power source.
>
> "I" have never heard of this but it sounds like a very good idea!!
>
> >
> >
> > This avoids putting the gap across the pig, which perhaps lets the gap run
> > cooler (no 50 or 60 Hz power arc), and may lead to higher efficiency and
> > better quenching. This would also aid in keeping nasty RF out of the pig,
> > and perhaps would reduce the need for RF filters. On the other hand,
the gap
> > losses are now twice(?) as high per bang. This is probably a lousy
setup for
> > NSTs as there is nothing to keep the NST voltage from soaring too high.
>
> The gap losses should be the same. The NST charging current... Oh.. I
just saw
> a problem.......
>
> First I'll go on with the thought. The gap losses are proportional to
current
> squared. The NST charging current squared is 0.060^2 = 0.0036. The primary
> circuit current is probably around 10 amps RMS so 10^2 = 100. Thus, the loss
> in the "firing gap" is 100/0.0036 = 27777 times higher than the "charging"
> gap. The charging current gap resistance may be higher (and probably is)
than
> the firing current so the loss is higher but it should not matter...
>
> Now that problem... The NST can only supply say 60mA Thus it will not
charge
> the cap in the time only a brief point presentation would give. The NST
needs
> the full "non-firing" cycle time (about 98% of the cycle) to recharge the
cap.
> Thus, your charging gap would have to be a long semicircle that would allow
> current to flow all the time except when the actual firing time comes.
> Technically, that is very possible to build but I wonder if the charging gap
> would tend to blow the arc all over as it's spinning - sort of doing the
> Jacob's ladder effect. The charging gap could probably physically touch the
> rotor since the current is fairly low to get around this.
>
> You could size the primary cap so that a failed firing would not over voltage
> it (as in LTR coils) or use REALLY good safety gap (properly set!! ;-)) to
> protect the neon in such a system.
>
> You have some very interesting ideas Steve!!
>
> Cheers,
>
> Terry
>
> >
> >
> > If someone has tried this, please let us know the results.
> >
> > --Steve Young