Re: Spark Gap Sustaining Current (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sat, 06 Oct 2007 20:32:55 -0500
From: Crispy <crispy@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Spark Gap Sustaining Current (fwd)

On Sat, 2007-10-06 at 13:12 -0600, Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Sat, 06 Oct 2007 12:45:44 -0500
> From: Bert Hickman <bert.hickman@xxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Spark Gap Sustaining Current (fwd)
> 
> Hi Christopher,
> 
> That's actually a very interesting approach! It seems to avoid the 
> catastrophic "flaming arc" problems of a classic resonant charging 
> circuit when the charging inductor value is too low, and yet DOES take 
> advantage of resonant charging of Cp via Lc.

Yeah, those are the problems that I was trying to solve with this idea.
It's the point of the rotary gap.

> 
> In your circuit (see below), there's no initial current flowing through 
> the inductor when gap A initially fires, and Cp is assumed to be zero. 
> As Cp charges through Lc, the voltage across Cp rings up sinusoidally, 
> approaching about 2*Vsupply. At this point, the charging current drops 
> to zero, the static gap extinguishes, and the dequeing diode prevents 
> any significant reverse current flow. As the ARSG rotates to position B, 
> there's still no current flowing through the static gap and it stays 
> extinguished as gap B fires, discharging Cp through Lp. As the ARSG 
> rotates back to position A, the static gap should reignite as long as 
> the voltage across Cs has not declined too much and there's little 
> residual charge remaining on Cp.

Yes, that's the concern I had.  The problem is that I don't think the
gap would reignite quickly because the voltage across Cs would decrease
from the amount originally required for firing when it is used to charge
Cp.  I was hoping that residual ionized trails in the static gap would
cause it to reignite at a lower voltage after the first firing.

> 
> I know of no simple way to estimate at what voltage the static gap will 
> eventually fail to retrigger, or how many successive presentations will 
> work before Cs must be recharged enough to re-fire the static gap. Try 
> it an see and let us know the results.

I've come up with formulas to calculate the voltage across Cs as a
function of the number of times the ARSG fires.  I don't need an exact
value for how many times it will fire, but I'm wondering if it would
even be reasonable to assume about 10 successive firings.

> 
> BTW, if you simply removed the static gap, I suspect this design would 
> work even better. The dequeing diode would still block reverse current 
> flow, thereby "trapping" 2*Vsupply across Cp, and the ARSG still serves 
> as the main switching element for alternate A-B switching...

I realize this.  The purpose of the gap is not to block reverse current
or to switch the resonant/charging circuit.  To better understand my
idea of its function, you can imagine it as a high voltage relay with
the coil connected to an oscillator at, say, 5Hz (or in that range).

Here's what I was thinking to come up with that idea:
I'm building all of this in my college dorm room.  I am also making sure
that I stay within all rules so they can't stop me fro doing so.
Fortunately, there is no voltage restriction on appliances.  However,
there is a wattage restriction.  No appliance can use more than 600
watts.  According to the Freau equation, this would limit my spark
length to around 40".  The special ARSG would probably provide some
performance increase, but even so, 40" is a little wimpy in comparison
to the TC that I built at home last year.  To get longer sparks, I had
to come up with some new idea.  My idea was to store up energy in a
capacitor significantly larger than the tank capacitor and discharge it
into the charging circuit.  So, say, the energy from maybe 10 AC cycles
could be stored in such a capacitor (which you have labeled Cs) and be
discharged into the charging circuit in the time of 1 AC cycle, which
would effectively multiply the energy available contributing to spark
length by a factor of 10.  The spark would be less often, but it would
be longer as well.

The main consideration here is the switching mechanism used to separate
Cs from the main charging circuit, so Cs has time to charge.  My first
idea was to use a high voltage relay as described above.  However,
ideally, Cs should be discharged whenever it reaches a certain threshold
voltage.  A static spark gap is ideal for this, as long as it continued
firing for successive ARSG presentations even if the voltage across it
dropped to somewhat below the initial voltage.

> 
> Please keep us posted on your results!

I sure will.  I'm in the process of building it, but it's going a bit
slowly.  The rules in dorms today are very strict, unfortunately.  I can
have very dangerous things such as high voltage capacitors in there, but
I have to jump through many hopes to even get access to a hacksaw.  I
just finished (20 minutes ago) sawing all of the G10 into the shapes
necessary for building the ARSG, but I'll certainly let you know how it
goes.  I'll post the equations that I derived as soon as I find where I
put them.

> 
> Good luck and safe coiling to you,
> 
> Bert
> -- 
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> 
> Tesla list wrote:
> > ---------- Forwarded message ----------
> > Date: Fri, 05 Oct 2007 11:56:33 -0500
> > From: Crispy <crispy@xxxxxxxxxxx>
> > To: Tesla list <tesla@xxxxxxxxxx>
> > Subject: Re: Spark Gap Sustaining Current (fwd)
> > 
> > Yep, that's it.  Thanks. 
> 
> <snip>
> 
> >>> The function of this special ARSG is to physically interrupt the
> >>> charging circuit from the tank circuit when the tank circuit is
> >>> resonating.  This prevents all of the loss and problems associated with
> >>> shorting out the power supply while the tank circuit resonates.
> >> I think I have it. Use a non-proportional font to see properly. The ARSG 
> >> alternates between position A - open - position B - open, etc...
> >>
> >>              Static   |\ |
> >>    + ----o----o  o----| >|-----o     o---------
> >>          |    Gap     |/ |      \              |
> >>          |             DQ     A  \    B        O
> >>    HV  + |                        o            O  Lp
> >>  DC In -----                      |            O
> >>        ----- Cs                   |     | |    |       Lc
> >>          | 0.44uF                  -----| |----o-----OOOOOOO---
> >>          |                              | |          =======   |
> >>          |                               Cp                    |
> >>          |                                                     |
> >>    - ----o-----------------------------------------------------
> >>
> <snip>
> >>
> >>> The function of the static gap is different from that of a normal static
> >>> gap.  The gap in this instance should not be considered as a voltage
> >>> controlled switch.  The gap's increased propensity to fire a second time
> >>> immediately after a first firing must be considered.  The gap functions
> >>> to pulse power from Cs into the rest of the charging circuit, providing
> >>> much higher power during several subsequent iterations of the ARSG than
> >>> is drawn RMS from the wall.  The special ARSG does NOT fire during the
> >>> majority of its iterations (during these iterations Cs is charging).
> 
> 
> 
>