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[AMPS] Vacuum Variable voltage rateing

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Subject: [AMPS] Vacuum Variable voltage rateing
From: dcoolica@planet.eon.net (Denis Coolican)
Date: Thu, 12 Apr 2001 21:00:36 -0500
I ran into problems with an air variable that I had increased the plate
seperation to handle more power at that higher Z on a 4-1000A..  I calculated
that the max RF peak voltage would be 4.5KV.   When I used the amplifier it 
would
arc over on voice peaks.  I hi potted the capacitor and sure enough it broke 
down
at 4.5 KV

I would say it would be best to hi pot the one you have so you know what you
really have.  If it is not 25% higher than what you calculate for peak RF 
voltage
I would look for another.

Regards

Denis VE6AQ

William Fuqua wrote:

>     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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