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Re: A real 1/4 wave TC



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Skip,

Since you had safety gaps each set at 1/8 inch, I'm guessing this probably prevented an overvolt. Since the safeties were fireing, this would take energy out of the charging system and prevent the killer voltages that could result with an SRSG, resonant charging, and no safety protection. Since the caps exploded and were hot, my first suspect is RMS current maybe due to high BPS when the safeties did fire. How did you set your safeties and do you have more specs on the cap (max voltage reversal, Ipeak, Irms). How many cap sections in series and/or parallel. When you do look at the cap, look to see if the dialectic melted and if there are any signs of pinhole failure caused by overvolt. Don't know how your caps would fail if overvolted. Do they fail open or short?? If the later, then maybe a short could cause temp problems, but it doesnt seem like your bang energy is large enough to cause an explosion. I'll work on the simulation this weekend assuming 35nf for your tank. It will be a simulation of only the charging stuff.

Gerry R.

Original poster: Skip Greiner <skipg@xxxxxxxxxxxxxxx>

Gerry
The cap was made by High Energy Corp in 1984. I do not know what the cap was made of except that it was oil filled. I talked to High Energy about 20 years ago and they told me then that I could run it in Tesla circuits without a problem. We did discuss the charge discharge cycles, current levels and the frequency range of about 100khz to 350khz. It apparently was a foil wound cap and was used in extremely high powered lasers where multiple pulses were generated. The cap had 6 sections. Each section was independent, rated .0275mfd @ 42kv. I had wired it for approximately .035mfd. I have been using the cap for at least 20 years without mishap. I have used it on coils operating above 5kw. When it failed, it blew up the case and sprayed oil all over the place. It obviously was HOT. I do not yet know the failure mode...will be doing autopsy in the next few days. As I said, I was only up to about 65 volts input to the NST and I was adjusting the gap phasing. Also was trying to get a good handle as to what frequency it was operating at. I had gotten rid of the racing sparks and the discharges were pretty well confined to the aluminum foil ring. The safety gap was firing intermittently. Discharges were 36" to over 40" and then BLAMO!
Skip