All I use the 3000 volt caps for are loading.
The tuning cap should be rated for at least
7.5 kv if you are going to run 6 kv Ep on a
4 X1, IMO.
You can get away with pushing limits on vacuum
variables that you never could on "bread-slicers"
because there is no dirt, corrosion, or humidity
involved.
A lot of the glass vacuum variables being sold at
flea markets/E-Bay are 50 years old, or so.
Caveat-emptor!
(((73)))
Phil, K5PC
Subject: [AMPS] Vacuum Variable voltage rateing
>
> Looking at Jenning's data on Vacuum Variable capacitors I noticed that
> the
> voltage rating on the capacitor is the Test Voltage and the working voltage
> is less.
> For example a 3000volt cap Cxxx-300-3 has a test peak voltage rating of
> 3Kv and a working peak voltage rating
> of 1.8KV. A 5Kv one has working voltage of 3KV and a 7.5 has working peak
> voltage of 5KV.
> So if I am running a 4-1000A with 5K plate resistance and 1500 watts out
> the RMS Plate voltage would be 2740 Vrms or 3872V peak. I can't use a
> 3000V cap based on those
> figures but must use at least a 7.5KV cap.
> So what gives. I expect most of us are pushing these caps beyond their
> working voltage limits.
>
> 73
> Bill wa4lav
>
>
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