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Re: [TCML] Spark gap Resistance



Hi all,

I wonder, could the spark gap not be tested in some way...

Years ago I tried a silly small test of placing a 500W NST across a 50W lamp via a spark gap. It was some 15 years ago so do not recall exactly, though I remember that the lamp did not light at all even though the gap was arcing. I suppose the test was daft anyway but hopefully sparks some ideas!

I wonder if current could be tested using a lot of voltage dividers and maybe measure the current on a regular meter some how, maybe use larger and smaller tank caps..

Or maybe just wind a step down down. say 50 turns primary and 5 turns secondary to step down the voltage to a readable level and try different tank cap values and measure the current.

Or maybe just a high voltage sense resistor of very low ohmic value and read the voltage drop across it could be the easy solution. Might be easy for someone who has a scope who can connect it in such a way to do the testing ?

Would be interesting to see how much current goes across the gap. Would be also interesting to vary the gap spacing and repeat all tests again. Such as testing a few tank cap values 10,20,40,80,100nF at 1mm increasements across the spark gap

There is a lot of problems though... for example if 40nF cap used pulsed 400amps and the 100nF could only pulse 50amps then it would make an unfair test. So as the cap size increased the cap itself would be limiting the current flow rather than the spark gap... It could also happen in reverse also, larger caps generally can pulse more current so may appear to make the spark gap conduct better the larger the cap value is.

So if the values of caps alters, then their own current rating should also be matched. It could take 100x 1nF caps to get to 500amps, or 1x 100nf cap may only be 100amps or could be 1,000amps!

Or maybe the spark gap current could be current limited to a set figure, then try spark gap spacing, and various tank cap sizes... then maybe half the current limit and repeat all tests again.

I think some of my points may get overlooked such as "the current of the caps does not really matter" kind of thing, but it maybe so, or maybe not, It would just be someone opinion which will "skip" over some vital test data. I think a lot of tests are needed to be done so solve all the questions.

Maybe it would work just using a very high current pulse 100nF cap and ballast to 10amp increasements.. and do the tests at 1mm increasements over the spark gap...

I assume 50/60hz over the gap during these tests. Frequency I think also should improve things though I think for now just the raw current tests and spark gap spacing are the most valuable aspects for the moment..

I personally think the wider the gaps are, with more current, and hgher frequency...the better the conduction will be.. Though I think I am on my own with that idea.

I think the issue needs to be tested and data/graphs drawn up to solve the issue once and for all... Cannot be that hard for some of you guys who have all the stuff to hand to setup and document ?

There would also be a "control test" where the test would be done with a link over the spark gap. Even linked vs spark gap is good info to have as right away you know what is lost over the gap in that one single test! Then increase the current pulses and work out if the gap conducts better or worse.. plus also spacing of the gap could well be important.. really a lot of tests but I think if all these tests are done and drawn up in a line graph we can see easily the differences vs the control (linked gap) figures.....


Chris


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