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Registered Member #103
Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845
What would you do if you came across a box of old Pyranol capacitors? I recently rescued a load of 2000V, 4uF Pyranol capacitors, in large-ish rectangular metal cans. A bit of googling reveals that they are quite old and contain PCBs! Are they safe to use in HV experiments as long as I stay within the ratings? What kind of performance would they give in a pulse application, or should I be thinking about trying to get rid of them instead?!
Registered Member #103
Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845
I've already looked into disposal, but wondered if I was just being a bit paranoid - afterall there are plenty of things like this still in use. I'm struggling to find info on this type of cap, i.e. internal impedances for pulse applications, ripple current etc, not sure if anyone has any experience of them? Unless they are really good performers, I'll probably try and get rid of them to be on the safe side.
Going to do a leakage test at a bit less than 2kV to see how they hold up. At only 8 joules each, I'm hoping there won't be enough energy for them to rupture their own cases if something did go wrong
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Avalanche wrote ...
I've already looked into disposal, but wondered if I was just being a bit paranoid - after all there are plenty of things like this still in use. I'm struggling to find info on this type of cap, i.e. internal impedances for pulse applications, ripple current etc, not sure if anyone has any experience of them? Unless they are really good performers, I'll probably try and get rid of them to be on the safe side.
Going to do a leakage test at a bit less than 2kV to see how they hold up. At only 8 joules each, I'm hoping there won't be enough energy for them to rupture their own cases if something did go wrong
Age-related dielectric degradation, leading to near silent arc formation, rising internal pressure from the the evolution of steam and gases from electrolytic decomposition, and catastrophic bursting failure are a common failure mode unrelated to energy stored. Indeed, failure of this type can even occur after the capacitor has been discharged, once chemical interactions have got into their swing, and have built up a good head of steam - very much like those rogue roast chestnuts, which sometimes explode even minutes after being taken from the stove.
4uF/2kV sound like HT smoothing capacitors to me, so if you must use them, you might want to down rate them by 50% to 1kV pk wkg to save your eyesight.
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Pyranol Capacitors
