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Re: Static Gap Break Rates



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Curt,

Excellent question. If we assume 120 bps is a properly set gap where the gap width sets the arc voltage, then the tank capacitance, charging voltage, and charging current will determine how fast the arc voltage will be reached to achieve 120 BPS during the time domain of the charging frequency. If the current is large enough, the cap can attain the arc voltage many times during the first 1/2 cycle. In the same respect, the current can also be so small that it may take several cycles to reach the arc voltage. The arc voltage time "IS" the BPS determinant.

In the real world, there are other factors that are not accounted for which affect the charging voltage and time domain. One factor is resonant charging. This is something that Gerry and I have been mulling over the past few weeks (how to account for it with some degree of accuracy). For now, it is not fully accounted (although, Rs and Rp measurement inputs help impedance accuracy. There may be resonant charging occurring depending on transformer and actual cap size. Bps is affected by this. It may be that the NST coupling may be needed as an input. This would obviously be one of those optional inputs. I can envision a help file for "how to measure transformer coupling" for those who wish to attain higher accuracy (should coupling be needed). Let's face it, there is information that requires measurement if we want to attain higher accuracy in our predictions.

On this same topic, I recently posted NST coupling inquiries and data. The reason I asked how to and then measured was to simulate resonance situations with different cap sizes, but while simulating, I found the NST coupling was critical in the model which stopped me in my tracks (because I first used a typical NST coupling value). After measuring and inserting the measured NST k value, the model now predicts resonance where it should be. One "cannot" assume a typical NST coupling value in this type of simulation (in other simulations, it may be of no consequence), but for this study, it is important. For example, a difference of 0.95 and 0.93 can easily mean a 30% error (no kidding!). There is a lot of study and "figuring out" to be done before this gets into Javatc.

Take care,
Bart

Tesla list wrote:

Original poster: "C. Sibley" <a37chevy@xxxxxxxxx>

In a discussion today I realized that I can't explain
some assumptions I've accepted regarding static spark
gaps.

I've run a lot of designs through JAVATC and have
accepted that the break rate increases as current
increases (assuming all other things remain same).
Depending on the current available the capacitor
charges quicker and the break rate goes up.  What I
can't come to terms with is break rates in excess of
120Hz.  Wouldn't the 60Hz input limit the break rate
to 120Hz for a properly set gap?  Based upon
experience I realizes there must be more going on than
just a simple RC circuit charging a capacitor. Am I
missing the point?

Thanks,

Curt.


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