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## Re: [Amps] Current thinking on HV supply bleeder current?

 To: amps@contesting.com Re: [Amps] Current thinking on HV supply bleeder current? TexasRF@aol.com Tue, 28 Feb 2012 17:04:16 -0500 (EST) mailto:amps@contesting.com>
 ```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. It 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 scenario. 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 KAPOW. Do be careful: there's danger lurking out there! 73, Gerald K5GW In a message dated 2/28/2012 3:49:50 P.M. Central Standard Time, audioguy@q.com writes: [forgot to CC this back to the list] Thanks, Jim. 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, Jim, N7CXI On 2/28/2012 1:34 PM, Jim Hargrave wrote: > Jim, > > The ARRL handbook has two recommendations. > > Bleeder resistance that will bleed the HV to 30 volts in 2 seconds after > shutdown. > > Another place it recommends a bleeder resistance that will equate to approx > 30% of the anticipated max load. > The later seems to be a carry over from Tube rectifiers, where the bleeder > 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 > W5IFP > > > > > -----Original Message----- > > From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On > > 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 this > > came up I seem to remember seeing everything from "HV safety bleed off > > only" up to a rather high number. > > > > So... 100 ohms per DC volt? That would work out to a convenient 400K, > > which could be four 100K in series, each with 1KV or so across them. > > > > Comments? > > > > Thanks, > > Jim N7CXI > > _______________________________________________ > > Amps mailing list > > Amps@contesting.com > > http://lists.contesting.com/mailman/listinfo/amps > > _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ```
 Current Thread [Amps] Current thinking on HV supply bleeder current?, Jim Barber Re: [Amps] Current thinking on HV supply bleeder current?, Jim Hargrave Re: [Amps] Current thinking on HV supply bleeder current?, Dr. David Kirkby Re: [Amps] Current thinking on HV supply bleeder current?, TexasRF <= Re: [Amps] Current thinking on HV supply bleeder current?, Jim Barber Re: [Amps] Current thinking on HV supply bleeder current?, Ian White GM3SEK