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Re: PSpice modeling of spark gaps
Hi Bart,
> Original Poster: "Barton B. Anderson" <mopar-at-uswest-dot-net>
<snip>
> > If Rbreak is sufficiently smaller (<0.1) than Zpri,
> > will its non-linear action noticably affect operation?
> >
> > Has anyone added an op-amp and current shunt to Sbreak
> > to more closely model the quenching?
> > --
>
> Greg, I haven't tried an op amp or current shunt to Sbreak, but I think
> modeling quenching more closely is a good idea. In Gary's post regarding
> behavior spice models, I think the site offered good information and
> sparked some ideas to those who took the time to read through it.
>
> I think it can be modeled by adding in behaviors derived from
> current/voltage levels, avalanche thresholds, and other associations in
> the gap. ("includes negative arc resistance, arc sustaining current, and
> accounts for variable dV/dt applied to the device") as stated by Gary.
> These parameters can be "modeled". Has anyone scoped out these or other
> parameters (real world measurements)?
>
> Bart
Closest I've come has been scoping primaries and deducing the basic
characteristics from the waveforms, then applying a bit of math to it
to reach some interesting conclusions regarding Q etc. I have also
tried using a bank of MOSFETs in place of the gap to investigate
quench issues and resonator action. Additionally, after forming and
opinion as to the nature of the real gap model, I did setup a
benchtop LC circuit and stuck in both back-to-back zeners and anti-
parallel diodes (low drop relative to the peak cap voltage). The
zeners were unrepresentative at the low voltages I was working with
but the diodes did a nice job *provided that the operating point was
carefully picked*. I found that I could obtain log, linear and
antilog responses depending on which circuit values I used so it pays
to be careful when using diodes of any sort as a substitute for the
real thing.
The most amazing finding the math revealed was that Q for a
tuned circuit with a gap in it couldn't be quantified as a fixed
value the way it can if there is normal resistance only. The math
showed that Q climbed with voltage and absolute losses increased with
current. The reason for this is that Vgap is not proportional to Igap.
Neither voltage nor current is a fixed quantity but continuously
varying in normal circuit operation.
Malcolm