Re: Spark Gap Sustaining Current (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 04 Oct 2007 19:00:20 -0500
From: Crispy <crispy@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Spark Gap Sustaining Current (fwd)

No, it's not really like that schematic.  I'm horribly at ascii art
schematics, and I can't draw in computer paint programs, but a much
better description of the simplified circuit is below.
First of all, the ARSG is not as you have depicted it.  This ARSG would
have 3 poles, instead of two.  There would be a central contact which
would alternate between two other stationary electrodes as it rotated.
Electrically, this behavior is similar to a SPDT switch that is being
switched back and forth very quickly.  In the below circuit description,
I will refer to the central pole as "central pole" and the poles between
which it alternates as "auxiliary poles".


- The transformer (12/30 NST) is connected to the 120VAC wall current.
- The output of the transformer is rectified by a hv bridge rectifier.
- The ~400nF capacitor that you have labeled Cs in your diagram is
connected across the outputs of the bridge rectifier.
- There is a series circuit from here composing the charging circuit.
It connects the + terminal of Cs -> Static Gap -> De-Qing diode -> one
auxiliary pole of the special ARSG -> (alternating via the rotary
contact) central pole of the special ARSG -> Tank Capacitor -> Charging
inductor -> - terminal of Cs
-  The primary coil is connected from the other auxiliary terminal of
the ARSG to the junction between the tank capacitor and the charging
inductor.

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.

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).



On Thu, 2007-10-04 at 16:47 -0600, Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Thu, 04 Oct 2007 10:52:06 -0500
> From: Bert Hickman <bert.hickman@xxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Spark Gap Sustaining Current (fwd)
> 
> Tesla list wrote:
> > ---------- Forwarded message ----------
> > Date: Wed, 03 Oct 2007 15:57:21 -0500
> > From: Crispy <crispy@xxxxxxxxxxx>
> > To: Tesla list <tesla@xxxxxxxxxx>
> > Subject: Re: Spark Gap Sustaining Current (fwd)
> > 
> > On Wed, 2007-10-03 at 07:59 -0600, Tesla list wrote:
> >> ---------- Forwarded message ----------
> >> Date: Tue, 02 Oct 2007 23:23:51 -0500
> >> From: Bert Hickman <bert.hickman@xxxxxxxxxx>
> >> To: Tesla list <tesla@xxxxxxxxxx>
> >> Subject: Re: Spark Gap Sustaining Current (fwd)
> >>
> >> Hi Christopher,
> >>
> >> Tesla list wrote:
> >>> ---------- Forwarded message ----------
> >>> Date: Sat, 29 Sep 2007 16:28:45 -0500
> >>> From: Crispy <crispy@xxxxxxxxxxx>
> >>> To: Tesla list <tesla@xxxxxxxxxx>
> >>> Subject: Re: Spark Gap Sustaining Current (fwd)
> >>>
> <snip>
> >> And, for a given bang size, overall spark length no longer increases 
> >> after you reach several hundred breaks per second... the discharges may 
> >> get hotter and more "frantic", but they get no longer.
> > 
> > Ah, Ok.  Why is this?  I guess there's another factor than what I
> > described, but what is this factor?
> 
> The other factor is the maximum output voltage of the coil. Eventually, 
> the electrical field at streamer tips becomes insufficient (due to 
> voltage drop along the leader-streamer channels) to support further 
> growth no matter how fast your break rate. Since the maximum coil 
> voltage (for a spark gap coil) is ultimately limited by bang size, 
> merely increasing the number of bangs per second eventually helps keep 
> keep existing spark channels hot, but does not aid in lengthening the 
> streamers once they have reached a certain limiting length. The 
> increased power from using higher break rates goes into making leaders 
> and streamers hotter, and spreading streamer tip activity over a larger 
> volume (i.e., generating more "frantic" streamer activity).
> 
> <snip>
> > 
> > Yes, I know that I need a deQ-ing diode.  The PIV should be about the
> > peak voltage of the power supply, and with proper overrating, I think a
> > string of 30 1N4007 diodes should work (which I have already built for
> > the purpose).  They are rated for 1A continuous current, but much more
> > peak.  With a charging inductor of about 25mH, I think this should work.
> > Also, because my charging inductor won't be very large, dwell time won't
> > be an issue (I've calculated it before and there's a significant
> > margin).
> 
> OK... but I'd recommend at least 1.5 - 2X margin on the dequeing diode.
> 
> > 
> > You seem to misunderstand exactly what gap I was referring to and what I
> > meant by sustaining current.  The gap to which I was referring was not
> > the gap that was part of the charging circuit in the rotary gap.  it is
> > a separate static gap would be in series with the charging circuit.  I
> > want this gap to fire at a certain voltage (approximately the peak
> > voltage of the electrolytic capacitor), but not quench until the voltage
> > is about half that.  Since arcs are sustained by current, my worry was
> > that the breaks in the charging circuit by the rotary gap would cause
> > this separate static gap to quench very quickly, maybe even after the
> > first firing, which would entirely defeat the purpose.  I want to keep
> > it firing for a number of rotations of the rotary gap, during which the
> > electrolytic cap will not charge to its peak voltage again.
> 
> OK. Is what you are proposing something like this, where gap "A" is a 
> static gap and "B" is your main ARSG gap?
> 
> 
>                  |\ |  =====   A            | |
>     + -------o---| >|--OOOOO---X------o-----| |--------
>              |   |/ |                 |     | |        |
>              |    DQ    Lc            |     Cp         O
>     HV     + |                        |                O
>   DC In    -----                   B  X                O
>            -----                      |             Lp O
>           Cs | 0.44uF                 |                O
>              |                        |                O
>              |                        |                |
>     - -------o------------------------o----------------
> > 
> <snip>
> > 
> > What's the acid test?
> 
> It's slang for the real thing - running it in a TC at minimum and 
> maximum break rates to see what breaks first...  :^)
> 
> > 
> >>> While watching these
> >>> discharges, I came up with an idea - what if this same "smoothing"
> >>> capacitor was discharged in impulses into the whole primary circuit?
> >> Directly firing the electrolytic bank into the primary would not be a 
> >> good idea. Electrolytics do NOT like the voltage reversals that occur 
> >> when "ringing" with a primary.
> > 
> > No, I do not want to directly fire the electrolytic capacitor into the
> > primary.  I know that electrolytics will not stand voltage reversals,
> > and it is only ever charged in one way.  The electrolytic is similar to
> > a DC smoothing capacitor, with the difference that it is periodically
> > discharged fully by the aforementioned static gap to provide
> > instantaneous power boosts.
> 
> OK... I think I see what you are tying to do (at least conceptually). I 
> need to see just how you physically plan to do this via a schematic (if 
> different from the above).
> 
> Bert