Jim, T=RC is the equation to discharge 65% of the energy. T is seconds, R
is ohms and C is farads.
Those big wirewound resistors have a voltage rating that should be
followed. An over voltage will lead to premature death by way of an open turn.
takes time but will happen eventually when you least expect it. Since they
are in series, only one resistor has to go open to create a death dealing
Over the years, I have seen this happen enough that I will not use wire
wound resistors for bleeders. Now 10 to 15 series connected 3 to 5 watt
resistors are used as needed to limit the voltage to 300v or less. This also
serves well as a hv meter multiplier.
Yes, it takes a while to bleed the voltage. If in a hurry, the tube idling
current will bring the voltage down to a few hundred volts in a few
seconds. Then the shorting stick only causes a modest pop instead a giant
Do be careful: there's danger lurking out there!
In a message dated 2/28/2012 3:49:50 P.M. Central Standard Time,
[forgot to CC this back to the list]
I believe your comments about heavier bleeder current being a carry-over
are probably true.
I'm going to pencil in four 100k, 20-watt resistors with a working
voltage of something greater than 1KV. I don't know if that would bleed
4KV in 32uF off in 2 seconds or less, but it would get there. If I trip
over any energy storage equations in the next few days I may try to work
it out just for fun.
Thanks and 73,
On 2/28/2012 1:34 PM, Jim Hargrave wrote:
> The ARRL handbook has two recommendations.
> Bleeder resistance that will bleed the HV to 30 volts in 2 seconds after
> Another place it recommends a bleeder resistance that will equate to
> 30% of the anticipated max load.
> The later seems to be a carry over from Tube rectifiers, where the
> assisted in parallel current regulation.
> My Clipperton-L has 800k which is distributed across the series filter
> capacitors. (HV is around 2800)
> That will give you a range that should fit most "Treasure Box" of parts.
> 73s de Jim
> > -----Original Message-----
> > From: email@example.com
> > Behalf Of Jim Barber
> > Sent: Tuesday, February 28, 2012 2:43 PM
> > To: Amps@contesting.com
> > Subject: [Amps] Current thinking on HV supply bleeder current?
> > I have a 3KV, 2A CCS transformer, and 32uf of filter. What's
> > the current
> > state of argument for appropriate bleeder current? The last time
> > came up I seem to remember seeing everything from "HV safety bleed
> > only" up to a rather high number.
> > So... 100 ohms per DC volt? That would work out to a convenient
> > which could be four 100K in series, each with 1KV or so across
> > Comments?
> > Thanks,
> > Jim N7CXI
> > _______________________________________________
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> > Amps@contesting.com
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