I was always told that something in the order of 20-50uF of C
was about right for EHT supplies. The energy stored being:
e = 0.5 x C x V^2
(from dim and distand recollection :-).
The bigger the cap bank the "smoother" your supply, but at the
same time it should be remembered that the diodes probably
coduct for less of the cycle and at a higher current.
For all of my recent (read in last ten years) amps (8877, 4CX1000,
3-500) I've used 12 x 470uF 400/450V SMPSU snap-in caps
rated at Iac = 2.5A @ 20 degrees, and with 40-50ohms of glitch
resistor.
So, compared to my 3900V PSU with 39uF of capacitance, your
250uF at 4500V is going to store about 8.5 times more energy and
be about 8.5 times more destructive - assuming you have the same
glitch resistor - and here's the rub: if you want to limit the discharge
(and hence destruction) then you need a glitch resistor in the order
of 400-500 ohms, and then if you draw 1A of anode current you'll
drop 400-500 volts...
Hence there's a lot to be said for correct dimensioning of the PSU
parts... YMMV especially if you *never* have flashovers!
Mike G8TIC/M0VHF
----- Original Message -----
From: "RICK COLE" <vk3ym@iprimus.com.au>
To: <Amps@contesting.com>
Sent: Tuesday, July 01, 2003 4:52 AM
Subject: [Amps] 2500uf @ 450v dc ElectroCaps
Ok Conrad
what is your reccomendation for the value to be used with a 4500v power
supply...I am interested as to why you make the statement "bad idea"
Regards Rick
Put 10 in series and you have a whole lot of joules to deal with in the
event of a flashover, bad idea IMO.
Conrad G0RUZ
FOR SALE:
ELECTROLYTIC CAPACITORS
2500 uF at 450V new, top-grade caps.
Cornell-Dubilier 400c series.
4" tall, 2" diameter.
Put 10 in series and you have 250 uF at 4500V DC
Put 20 in series and you have 125 uF at 9000V DC
Pricing:
QTY 20 or above at $10.00 each
QTY 10 or above at $12.00 each
QTY <10 at $15.00 each
Shipping Additional
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