........
>Now I have a sordid confession to make. I still toy with
>power supplies that feature resonant-choke-input filters.
>Nearly everyone else at the ham level uses capacitor-input
>filters, at least for HV supplies, for reasons of which I am
>sure most of us are aware.
For RTTY, the best way to fly.
......
>....... I have a follow up question about flash-
>discharge caps.
>
>The consensus seems to be that average ripple current is the thing
>that impairs the longevity of flash-discharge caps. when they are
>subjected to DC filter applications. The thinking is that the
>voltage breakdown is the long-term result of heat rather than
>excess potential.
Yes, the higher ESR in the plates makes more heat, which can crack the
seams, the oil leaks, and the unit breaks down.
>The wisdom behind the 50% or 60% derating
>figure is that the reduced ripple-current throughput that is apt
>to occur at the lower potential is easier on the cap.
Sounds pretty ok.
>FB, I love it.
>
>Does it follow from all of this that a resonant-choke-input filter
>requires less derating of a flash cap than does a capacitor-input filter?
Yes, because the ripple current in a C-input filter is probably a dozen
or so times the ripple current in the post inductor C in a resonant-choke
filter with equiv. output volts/amps..
>With the latter class of filters, the cap is asked to do the "heavy
>lifting" with respect to smoothing of ripple. With the former
>class of filters, the resonant-choke circuit takes the brunt. Is
>it reasonable to assume that a flash-discharge cap will survive
>longer, and be safe with less derating, when it follows a
>resonant filter?
.... and well said, methinks.
cheers, Bob
Rich...
R. L. Measures, 805-386-3734, AG6K
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