Group, During my days of interest in antique radios, I learned that the dielectric between aluminum plates was formed by passing current in one direction to build up an oxide coating on the plates, which became the dielectric. The thickness is directly proportional to working voltage and inversely proportional to capacitance. As we learned from reforming old caps, the oxide thins when there is no voltage on the cap, but can be restored by passing several milliamps through the cap. Applying rated voltage before it was formed would destroy the cap by welding spots of the plates together.
I'm not sure that this applies to modern caps. As to the temperature rating, a high temp cap run in a cool environment will be as unhappy as someone transplanted from Miami to Minneapolis in the winter. It may work, but it will be very unhappy - so it depends on your empathy for the cap. There ought to be a way to work precision time into this thread, but I can't think of one. Bill Hawkins -----Original Message----- From: Poul-Henning Kamp Sent: Tuesday, June 21, 2011 2:40 PM In message <4e008a73.50...@erols.com>, Chuck Harris writes: >and yet, I find that some electrolytic >capacitors that have been run at lower than normal voltage improve markedly >when "reformed" by applying rated voltage through a 10K resistor for a >couple of hours. I noticed in a datasheet at one point, that the capacity only was warranted above a certain percentage of rated voltage. No explanation was given. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.