Hi Miles, No need to send. But, do a little math.I'm sure you've heard of the typical 30kV per cm (76kV per inch) for breakdown in air for electrodes about 1cm in size and in a uniform field. This value is the voltage gradient at which breakdown occurs, granted under specific criteria. However, the criteria changes (pressure, distance, size, etc..). Normal breakdown is on the order of 26kV per cm or 66kV per inch.
66kV per inch of breakdown is 0.015" per 1kV. This is 1.87 times smaller a gap distance than the gap distance you quoted of .028" per 1kV. What is being said with that statement is that breakdown of the gap should be set so that we assume breakdown in air occurs at 35.7kV per inch. Well if this is true, then we should be able to set that gap distance accordingly, apply 35.7kV, and breakdown will occur. ??? Guess what, it won't.
What will occur is that the cap continues to climb until breakdown finally does occur. If 66kV per inch is correct, then your 12kV transformer will see from the charge on the cap roughly 22kV across it's secondary winding at the point in time when the gap shorts out the transformer during conduction in normal operation.
But lets be practical. There is absolutely no doubt in any seasoned coilers mind that if you open up the gap distance, you will achieve a higher bang energy across the gap "due to the increased voltage required to arc the gap". Some transformers can take this, and some cannot. I'm not sure where Richard acquired this gap setting, but I suspect it is one of these statements "I have found that x works great for these gaps".
It is fine to increase the gap as you feel comfortable with (hell, I won't stop you). But as far as Javatc's recommendation being in question, can you at least tell me what it is your questioning? Because it's not just Javatc your questioning, but many papers on the subject of breakdown.
Regards, Bart Miles Mauldin wrote:
Right, it is RMS. This is from an archive mailing with Richard Quick amswering questions and a list member asking them. I can send the link later if you wish(don't have links to it on phone).Well it's 13 electrodes (12 gaps). Although being quenched by a muffin fan, I still question the gap recommended by JavaTC.Best Regards, Miles Sent from my iPhone On Apr 16, 2010, at 8:52 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote: Hi Miles, The .028" gap per 1kv seems awfully large. Is that 1kvrms? (Hope so ;-) ). I am also curious if this value is empirically based on a particular gap or electrode radius? One could go on and on I guess. In the end, with Javatc, it is simply calculating what should be the breakdown value based on cap size, current, electrode radius, etc.. Javatc is not trying to err on the side of safety (keeping a user from opening the gap up too wide) but is simply showing a breakdown value based on common calculation. Obviously, many variables come into play that change daily, so use it as a guideline or a starting point. If I were you, I would set the gap with transformer and no cap, and verify arc distance with the radius of electrodes and air flow that you will be using. Even if it's only 2 electrodes for now, that should be fine. Then build the gap to the total gap distance using all electrodes. In operation, there is also resonant charging and various anomalies that affect the actual charging of the cap. This will show itself in a static gap as a higher bps. How much higher is dependent on those variations from design in the charging circuit. Hope that helps, Bart Miles Mauldin wrote: Hi All, Hope I am getting close on the final design, but I do have a couple of questions. Here's my calculated JavaTC results. "http://www.cmnow.com/TeslaMan/JavaTC-Final.jpg"; _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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