ORIGINAL MESSAGE: (may be snipped)
On Wed, 05 Jun 2013 09:58:11 -0700, you wrote:
>
>Why such a large capacitor for the power supply? Surely 680 uf, one tenth of
>what you plan
>to use, would be more than enough, even given the low impedance of the load.
>The extra
>capacitance just makes the PS more dangerous in the event of a short or arc,
>and will take
>longer to discharge when you turn it off.
>
>You might need to take some extra precautions to protect your diodes from
>transients if
>the PS is connected directly to the line.
REPLY:
Why such a large capacitor? 6800 uF with an eight amp drain gives about a
1.5 % ripple. 680 uF would be ten times more and I think that's too much.
By comparison, a typical commercial tube type amp running 3 kV at 800 mA
with a 50 uF filter has a bout 2.2% ripple, and that seems to be
acceptable.
I could go down to 4700 uF if I could find one. These really hi cap hi
voltage units are kind of rare.
Transient protection is probably a good idea, but with such heavy diodes and
a massive capacitor, any transients are likely to be absorbed. Remember,this
is a full wave bridge so transients of either polarity would be absorbed. At
least I hope so. :-)
73, Bill W6WRT
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