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Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
We got bare capacitors because we were potting them inside of kicker magnets (a low-ish impedance transmission line whose b-field is used to kick a particle accelerator's beam) and didnt need the extra bulk of the epoxy. The potting was sylgard.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Steve Ward wrote ...
We got bare capacitors because we were potting them inside of kicker magnets (a low-ish impedance transmission line whose b-field is used to kick a particle accelerator's beam) and didnt need the extra bulk of the epoxy. The potting was sylgard.
i guess some dont even need the leads, preferring their own connections.
Registered Member #599
Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624
Hazmatt_(The Underdog) wrote ...
I can attest to RTV silicone, its a total B@#%%ch to remove. These are TDK 40KVDC caps, 5mm thread. I'm not sure what they were used for in the past other than for some kind of laser supply, I use them for my TC bank and they work very well. The only real purpose I can see for encapsulating them in RTV is to reduce corona, which would be enormous for a large bank of these.
I have very same caps and they work really well in Marx generator. I have ran my generator for couple hours total with 0.5Hz rep rate with no problems at all :)
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
jpsmith123 wrote ...
Does anyone know what kind of failure modes these caps have? And what kind of continuous current they can handle?
Has anyone ever had one fail?
I bought 10 30kV 1nF doorknob caps ages ago and one of them died when I was using it to limit a 15kV NST's current. I had it in series with one output and was drawing very low current arcs, and it failed short after like 5 seconds :(
I'm guessing it must have been a manufacturing fault, because the other 9 have survived much worse abuse.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
Thanks for the reply.
I'm thinking about buying some ceramic doorknob caps. Being that they're so expensive, I may even get some used ones. It seems there's not much to go wrong...they're like a piece of solid rock with electrodes...
I just wonder what kind of aging processes, if any, are occuring in the dielectric?
Registered Member #1565
Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159
Just for an idea, can the ceramic doorknob caps be the same deal as ceramic smd caps. I have seen something about SMD caps loosing capacitance, and can be restored by heating up to the currie point (as for the SMD type.. that would for instance be soldering)
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What's the internal construction of TDK UHV series ceramic "doorknob" capacitors?
