>Would some please explain why 450V appears to be the maximum rating
>available today?
This appears to be pushing the envelope on aluminum electrolytic
capacitors.
>Many years ago 500V, 600V and even 800V were available.
Yeah, my TS-830s had a pair of 500V electrolytics. They were the first
thing to fail. I replaced them with (4) 300v 105 deg C Matsushita
electrolytics
>How critical is that 450V rating?
I believe it.
>Will a CGS computer grade cap with a
>500V surge rating run long term at 510V...with loading reducing the DC to
>435V?
I conducted some bench tests, and this is my conclusion. As long as the
cap. is cool, a bit of over voltage does not hurt anything. However,
when the capacitor is warm, there is a potential problem. As the
capacitor warms up, leakage current increases, which increases leakage,
which increases temperature, which increases leakage current...---on and
on..
in actual use, ripple current flows through the capacitor, which, due to
ESR, causes temperature rise. If voltage is not reduced promptly, a
thermal runaway condition could result.
>I have been experimenting with a new SB-220 xfmr and Harbach's matched
>capacitor bank. The caps have been running for 48 hours at 510V without
>failure and they are only barely warm to the touch. With Allen's matching
>and the 100K equalizing resistors the voltages across each cap are within
>5 volts. The xfmr will be redesigned for a bit lower voltage anyway but
>this capacitor rating has got my interest up.
I would not feel comfortable exceeding 3400v on standby with (8). 450V
electrolytics in an SB-220. The cooling fan in a 220 puts zero air flow
on the filter capacitors. If the capacitors even begin to get warm, one
could be in for a nasty surprise.
For more suds, how about a mod to drop in (3) 8877s. The existing 5v at
30a would light the heaters, FB.. ......just joking, Carl. Something
with handles would be a lot less expensive and much easier to drive. .
Rich---
R. L. Measures, 805-386-3734, AG6K
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