Hi Bert,yes these caps indeed come out of Linac's. I think it will be very difficult to get some information concerning their construction from the manufacturer (it seems that such big companies aren't interested in requests from some hobby tesla coil builders), so I have to test them and see, how their behavior is in a tesla tank circuit. The good thing is, I'm not dependent on this caps, because I have plenty of other pulse caps (Maxwell) in stock.
I will let you know, when I've done some testing. Regards, Stefan----- Original Message ----- From: "Bert Hickman" <bert@xxxxxxxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> Sent: Thursday, October 23, 2014 5:54 PM Subject: Re: [TCML] Pulse Cap question + VIDEO
Hi Stefan,Nice find!! The high rep rating suggests that these caps may use low-loss polypropylene-foil-oil or polyester (PET/Mylar-foil or PET-Paper-foil) construction. Hopefully, you may be able to get the actual dielectric specifications from Haefely Hipotronics.If the caps use a PP dielectric system, they should easily handle 400 BPS in short intermittent TC usage. In PFN application, each cap would normally see no more than 10% voltage reversal. Assuming 10% VR, don't charge them above 22 kV in TC use. You may also want to use sufficient tank inductance to limit peak primary current to no more than 400A. This assumes these caps were originally part of a 50 ohm PFN that delivered half of the line voltage (or 20 kV) into a 50 ohm load.If the caps use a PET dielectric system, then they may overheat in TC usage. Unless you can confirm construction with the manufacturer, use them cautiously in a TC (short duration runs and closely monitor for signs of excessive heating). Allow sufficient time for heat to propagate from the inner part of the capacitor rolls to the metal case.Any idea what kind of equipment these came from? I've seen similar capacitor modules used in some medical LINAC's.Good luck, Bert Teslalabor wrote:Hi Bert, much thanks for this info. I was already on the road for picking up the PFN's and read your mail via smartphone, just in time. So I was a little bit forewarned that there could be internal inductors. Then I saw the caps and what a relief - I was very happy to see nice EXTERNAL inductors mounted to the insulators :-) Looks pretty cool, never seen anything like this before, made a short video: https://www.youtube.com/watch?v=mO7sVuXbDYU So after we eliminated the 4,5µsec thing, I think when removed the inductors, these caps will give damn nice low inductance tank caps for some biggg tesla project :-) The capacitance can be varied in 30nF stepsup to 210nF, when all 7 caps are in parallel. The 2 big ones, as mentioned:40kV 7 x 0.03µF 300pps (4,5µsec) The small one: 25kV 7 x 0.01µF 360pps (4,0µsec) By the way, what would happen, if you push the 300pps caps to lets say 400pps? Thermal issues? Think this would be not critical for short run times? Regards, Stefan<snip> _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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