Hi Jim,
Good to hear you're still actively doing some man-sized coiling :-) I was wanting to ask you about your GA pulse caps. Are they the high pps rated type (I think the 37xxx and possibly the 35xxx series as well are typically the higher pps rated ones of the GA/Maxwell product line)? I have found that the Maxwell 0.1 uFd, 75 kV rated one that is of the typical 31xxx (393?) low pps rated (1 pps) works excellently in my big coil and has never shown significant warmth above ambient temp that could be felt externally, even after extended high powered runs. And even though my cap was used when I obtained it, the sweet thing about it is that I have 3 identical spare units (ebay) :-) Although they are rated for low pps, the 75 kV rating does offer a higher ceiling and since my transformer is 14.4 kV, I don't think I should have to worry too much about "bumping" that ceiling, since the general rule of thumb says the primary cap rating should be at least 2x (Vpk) - 16800 (assuming variac set for max 280v input to 14.4 kV piggy) x 1.41= 23,688v x 2= 47,376 volts. So, it would seem that a 50 kV rating on the primary cap should be sufficient and 75 kV would just be extra insurance. However, both Cameron Prince and I have had the same Hipotronics 0.1 uFd, 50 kV rated cap (rectangular oil-filled metal can with a single standoff bushing terminal) to fail in our large SG driven coils, and the failure was obviously over volt related, as in both cases the cap had not shown signs of excessive external warmth before the failure occurred. Also, an autopsy of my particular cap showed no signicant burning of the dielectric inside, just a single "burn through". No spectacular case rupture when it failed either, just the coil's output suddenly dying and the cap's terminals showing a dead short. Also, even if a cap is rated for just 1 pps at its rated voltage, keeping the operating voltage at less than say 50% of the nameplate rated voltage is supposed to increase the cap's shot life expectancy exponencially. Not sure what the deal was with the Hipotronics caps, though, as I had obtained both of the caps in question "unused" from Jeff Parisse of KVA Effects. He had mentioned that he was looking to "upgrade" his caps, though. From mine and Cameron's personal experience with these units (maybe 2 hours of run time before failure?), I'm thinking Jeff's "upgrade" may have been for a good reason.
Has anyone else had any experience with these Hipotronics capacitor units? Sorry, I can't recall any part number and I'm not sure that they even had a part number on the label and were probably custom built units.
David Rieben
Jim Mora <wavetuner@xxxxxxxxx> wrote:
>Hello Tesla Friends,
>
>I have been away for a few years on other quests but still have all my Tesla
>Coil stuff. Recently, I finally got my 3P 208v wye 15KW <cont> Diesel genset
>running.
>
>I have a Cold War era Raytheon 3P DC charger that uses (6) 8020 Tube
>rectifiers - very Frankenstein -ish! The output is through a very large
>Inductor (Says 150 Henries) and is 24KV(-) the (+) side comes from the
>filaments, the minus is on a 12" standoff insulator! Anyway, I plan to wind
>a 12" form (thin wall PVC) to a 5:1 ratio. I have (2) unused .1uf General
>Atomics large pulse duty Caps @ 50KV. I realize the out power will be a
>linear rise as BPS goes up. I haven't tried to predict resonate charging nor
>want it per say, a visit to Richie Burnett's site is needed.
>
>* I do "not" have a suitable Spark Gap and will either build one or buy one.
>I have an ample supply of G10 that is suitable but lack machining tools. I
>also have (8) .5" x 2.25" pure tungsten slugs (intended) and numerous .25"
>which probably wouldn't stand up for the rotor.
>
>There is no rating of current I/0 on the transformer / supply tank. The
>internal transformer is a 208 wye in ?HV delta out, there is also a assumed
>isolated internal filament transformer with 1 P 120v input I see that (1)
>8020 can run at 100 - 750 ma 2A peak. Anyone want to do an educated guess on
>the output of the supply limits? BTW the + terminal is on a close to case
>standoff so it is meant to be -24KVDC above ground out. I have the schematic
>with no ratings stenciled on the tank. It is oil filled.
>
>Thanks Much,
>Jim Mora
>
>You can contact me off list if you like: wavetuner@xxxxxxxxx I also have a
>14,400 5VKVA Pig as well as a large GE potential transformer of the same
>rating. So if the DC charging fails, its back to classic design.
>
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