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Re: triggered RQ type SG???
All,
Interesting discussion!
How about triggering from the center of the array of gap electrodes
using a linear Vacuum Cleaner or Scott gap and an odd number of
electrodes. For an NST-driven system, the ends of the spark gap array
will be driven equally above and below ground. An AC-coupled HV trigger
pulse could be injected at the middle gap electrode of the array. This
should induce breakdown of one half of the gaps, thereby triggering the
subsequent cascade breakdown of the remainder.
One could even "enforce" 1/2 of the applied potential at the center
electrode by means of high resistance HV equilizing resistors, similar
to the approach used in commercial field distortion gaps. And, by using
high velocity airflow through the gaps, fairly good quenching could also
be assured. The HEI coil could be driven from a pulse source that's
referenced to the incoming AC line but adjustable relative to phase to
adjust triggering. This idea's beginning to sound like it has potential
(NPI)... :^)
To NST To NST
HV bushing HV bushing
----0 0 0 0 0 0 0 0 0----
| | |
| | |
|--/\/\/\--o--/\/\/\---
R1 | R2 R1 = R2 = 50 Meg or greater
|
|
-----
----- 30 kV+ doorknob cap
|
|
to HV trigger source
(ignition or HEI coil)
Safe gappin' to you!
-- Bert --
Tesla List wrote:
>
> Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>
> Not a bad idea...
>
> Fruengel had a similar design with a bunch of ferrite toroids around the
> main lead that would saturate when the main discharge occurred. When the
> trigger pulse happens, the ferrites aren't saturated, so the inductance is
> high, but then, when the gap breaks down and the current increases.
>
> You'd probably have plenty of series impedance in the secondary of the auto
> ign coil. You could always couple through a cap. I don't think you'd need
> the spark gaps, the rise time of the auto coil pulse is plenty fast enough,
> because what you are really looking for is the overvoltage anyway. An HEI
> coil puts out 40 kV, and if your gap is set for ca. 25-30 kV, you're all
> set. You could always use two coils in series anyway.
>
> Here is the big question: Quenching... will the RQ type gap quench quickly
> enough. One advantage of rotary gaps is that they force quenching.. and
> allow the use of DC supply. I suppose you could use a charging inductor, or
> some sort of staged gap.. Fire the first gap to complete the primary LC
> circuit. After it has rung down, the gap self quenches. Then fire the
> charging gap from a stiff DC source to charge the C back up. When the C is
> charged, the charging gap shuts down.
>
> This whole idea is quite intriguing though...
>
> >>3) Series triggering like is used in big flashlamps. You might have a
> >>problem getting the rep rate, though. This relies on a pulse transformer
> >>that is in series with the load. A big pulse through the primary induces
> a
> >>high voltage in the secondary, which overvolts the gap breaking it down.
> >>
> >How about adding a small series inductance in series with the gap (existing
> wiring might be enough).
> >Set up a trigger coil (e.g. ignition coil), such that it connects to each
> end of the gap via spark gaps.
> >Using spark-gaps to couple means the risetime of the trigger pulse is
> extremely fast, and so the abovementioned inductance prevents the
> >high-voltage firing impulse being dissipated through the main cap.
> >You will also want some series resistance in the firing cct secondary,
> >so the main discharge isn't tempted to happen through the trigger
> >coil.
> >The ignition coil could be fired with a fairly simple triac phase-angle
> light-dimmer type arrangement.
> >
> >
> >
--
Bert Hickman
Stoneridge Engineering
http://www.teslamania-dot-com