Even 2 kJ is dangerous. The large GE capacitors that we use at work,
run about 4 kJ each in operation. In 2001, we began to loose them,
explosively. Each time, the metal can peeled open like a can opener did
it - scary. Like others said, must prepare for the eventuality that a
bug, fly, mouse decides to bridge across a capacitor terminal, to
discharge that energy in one place, without a glitch resistor to protect
it. All of our high power RF amplifiers use purely Capacitive power
filters, on order of 100 - 250 uF, as they are pulsed systems and
require stored energy to supply the pulse, i.e., pure economics. LC
would have the ringing problem at each pulse, just like CW will do. It
can be designed to move the ringing away from the excitation pulse rate,
if careful.
Stored energy makes me wary every time I have to safe a cap bank and go
inside. My present project is using 88 kJ of stored energy for 150 amps
of plate current. I have only witnessed an accidental discharge once,
through some resistance, thank goodness. I was seeing a white spot for
an hour and everyone in the building came to see what the dynamite was
about.
But on the other hand, in broadcast transmitter with tubes, class C FM,
i did not waste time in deciding to use an LC filter (in 1980s) which is
much safer. With constant load, it was a perfect match. And I did
resonant choke design also. It worked very well. But not something you'd
want with a pulsed load.
There are reasons for both approaches, so we don't need to beat each
other up over it.
73
John
K5PRO
> Here's an opinion for you: 162 uF at 5 KV is asinine. I don't have
> time to do the equation but I am pretty sure the stored energy is
> somewhere between 5000 and 10000 Joules.
>
> %%% 5 kv @ 162uf = 2025 joules...so what.
> When tapped for 7700 vdc no load, it then becomes 4800 joules.
>
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