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Re: Double Throw Spark Gap (fwd)
---------- Forwarded message ----------
Date: Thu, 11 Oct 2007 00:30:38 -0500
From: Crispy <crispy@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Double Throw Spark Gap (fwd)
If I understand you correctly, you're saying that you think that the arc
on the charging cycle might quench prematurely. I have considered that
this could be an issue, but I don't think it will cause significant
problems. The dwell time is more than sufficient. I've done the
calculations and there's a very large margin between what I'm operating
and when the dwell time would become insufficient. The problem that I
was considering and I believe that you are too is that there might not
be sufficient current in the charging arc to continue to charge the tank
capacitor to its full extent. To an extent, it will indeed limit the
voltage to which it is charged, but with a spark gap with close
tolerances, I believe that the effect would be minimal. The peak
charging current with my setup will be around 13 amps. Using this with
a very rough estimate, the tank cap should charge to a voltage very
close to 2x vSupply (due to the charging inductor).
If you're referring to when the arc will start, there should be no
problem there. I've tested it with an NST and the arc forms just fine.
Regarding your paragraph on loss when the supply is shorted:
When I first saw the schematic for a classic disruptive discharge TC,
this is the first thing that came to my mind. I didn't think too much
of it at the time, because I knew that others had built TCs using that
principle that worked very well. In the classic TC, what it essentially
boils down to is, while the gap is conducting, the power supply is
shorted with minimal resistance. The effect of this resistance is even
minimized because the gap is firing at the peak voltage of the cycle.
With an unballasted power supply, we know what this can do. It
drastically increases the current draw at that point and wastes a ton of
power. With a ballasted power supply, I imagine that the shorting of
the gap would cause all remaining energy in the transformer core,
ballast core, and possible leakage inductance, would be lost to heat in
the gap. This could represent a significant loss in some setups.
On Wed, 2007-10-10 at 22:02 -0600, Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Wed, 10 Oct 2007 20:56:55 -0700
> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Double Throw Spark Gap (fwd)
>
> Hi Chris,
>
> I admit I still have some study to do regarding your mechanical
> approach. I've just been a wee bit busy with other off-list things
> lately. When I'm referring that I don't understand the mechanics, I mean
> mechanics in terms of how the arc will quench on the firing mode (as
> hoped) and how this will affect the recharge time, etc. With high
> voltage energy like this, the arc will start "and finish when it's
> finished" and not necessarily when you wanted it to. Such are the
> problems with this high voltage hobby. But, I'm hoping to learn
> something new here!
>
> You brought up an interesting question: What type of loss do we actually
> see with the transformer periodically shorting? I'm unsure about that. I
> have never thought much about it, but it could be a fair amount. So I'm
> hoping for all the best with this experiment. Chris, it's this type of
> experiment that the TCML is all about! Glad to see you working on it!
> For better or worse, it's one of the most interesting I've seen in a
> long time.
>
> Take care,
> Bart
>
> Tesla list wrote:
> > ---------- Forwarded message ----------
> > Date: Wed, 10 Oct 2007 15:38:41 -0500
> > From: Crispy <crispy@xxxxxxxxxxx>
> > To: Tesla list <tesla@xxxxxxxxxx>
> > Subject: Re: Double Throw Spark Gap (fwd)
> >
> > Bart,
> > The mechanics are fairly simple - I posted pictures earlier, if that
> > helps. A rotary contact just switches between two different sets of
> > stationary contacts.
> >
> > On an unrelated note,
> > Someone mentioned that this could be used with an unballasted power
> > supply. Although this would theoretically work, I wouldn't recommend
> > it, "just in case". If something went wrong and shorted out the supply,
> > bad things happen.
> >
> > On yet another unrelated note,
> > Does anyone have any feedback on my initial proposition of seriesing a
> > static gap in the charging circuit to pulse power? My goal for this
> > project was to get the largest sparks possible while still staying
> > within my dorm's 600 watt power limit. The DTSG should help eliminate
> > losses involved in shorting out the power supply while the gap fires,
> > but the difference this makes probably wouldn't be too big. Pulsing
> > power (at a layer in addition to the normal disruptive discharge) could
> > increase spark length, however. My idea is to add a mechanism to
> > disrupt power at a lower frequency (say, 5Hz or less) in the charging
> > circuit.
> > In the schematic at
> > http://tangent.cluenet.org/~chules/hv/tesla/ardtsgschem1.png , my basic
> > idea can be envisioned by adding a switch between the HVDC power supply
> > and the de-Qing diode. When this switch is open, the "smoothing
> > capacitor" would be allowed to charge to essentially full capacity.
> > When this switch was closed, the power available to the charging circuit
> > would be the power of the direct supply added to the stored energy in
> > the smoothing capacitor. With a ballasted supply, this would allow for
> > much higher ARSG break rates and larger tank capacitors than would be
> > plausible with just the supply itself, and therefore longer sparks for a
> > given average power input.
> > Such a high voltage switch would be possible to make, but would only
> > yield one "visible" (as soon by an observing human) spark per switch
> > contact. I've been considering different mechanisms, and I'm wondering
> > if a single unquenched static spark gap would work, due to residual
> > ionized trails. Any thoughts? I've also considered a high voltage
> > relay.
> >
> > Chris B
> >
> > On Wed, 2007-10-10 at 08:07 -0600, Tesla list wrote:
> >
> >> ---------- Forwarded message ----------
> >> Date: Tue, 09 Oct 2007 21:44:55 -0700
> >> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
> >> To: Tesla list <tesla@xxxxxxxxxx>
> >> Subject: Re: Double Throw Spark Gap (fwd)
> >>
> >> Hi Adam,
> >>
> >> It's going to charge in the low millisecond range and discharge in the
> >> low microsecond range (in a Bang!). No doubt about that. Electrically,
> >> he's attempting to separate the charge circuit from the discharge
> >> circuit. But I don't completely understand the mechanics of how this can
> >> be done. I'm just sitting back to see what comes of this experiment.
> >>
> >> Take care,
> >> Bart
> >>
> >> Tesla list wrote:
> >>
> >>> ---------- Forwarded message ----------
> >>> Date: Tue, 9 Oct 2007 03:46:42 -0700 (PDT)
> >>> From: Yurtle Turtle <yurtle_t@xxxxxxxxx>
> >>> To: tesla@xxxxxxxxxx
> >>> Subject: Double Throw Spark Gap
> >>>
> >>> I haven't really been following this thread, so
> >>> forgive me if this comment has already been addressed.
> >>>
> >>>
> >>> Regarding the following circuit:
> >>>
> >>> http://tangent.cluenet.org/~chules/hv/tesla/dtsg.html
> >>>
> >>> Does everyone think the cap can charge adequately in
> >>> the same amount of time it can discharge? Without
> >>> doing the math, I gotta believe that if one set of
> >>> flying electrodes zooms around at several hundred rpm,
> >>> the presentation time for the charging portion will be
> >>> too short to fully charge the cap. After all, most rsg
> >>> coils are charging the whole time they aren't
> >>> presenting (well not exactly). I guess you gotta know
> >>> the dwell time and the size of the pig feeding this.
> >>>
> >>> Adam
> >>>
> >>>
> >>>
> >>> ____________________________________________________________________________________
> >>> Boardwalk for $500? In 2007? Ha! Play Monopoly Here and Now (it's updated for today's economy) at Yahoo! Games.
> >>> http://get.games.yahoo.com/proddesc?gamekey=monopolyherenow
> >>>
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