Re: HV supply regulation

On the tube sitch folks, I'd aviod the 4CX10000's etc as they require 
monster filament supplies ie 7.5v, 100a. There are quite good pulse 
modulator triodes and tetrodes available quite small - the C1166 (eev) 
can hold off about 18kv and peak anode currents to 20A . The main 
limiting factor is plate dissipation but you could run a few in parallel 
- also eimac 4PR60c - 4PR1000 - 60 to 1000watts pdiss respectively. Also 
bigger switch tubes in Xray machines can hold off 100 - 150 Kv if 
immersed in oil. Good idea to have tube holdoff rating a bit higher than 
unregulated dc supply vtg. for a 7kv supply, I'd think about using a 15 
kv tube. If your tube dissipation is going to be very high, 4CX10000 
could be an option

>From tesla-request-at-pupman-dot-com Wed Jan 13 02:14:30 1999
>Received: from pupman.pupman-dot-com (root-at-pupman-dot-com [])
>	by ez0.ezlink-dot-com (8.8.8/8.8.8) with ESMTP id DAA30073;
>	Wed, 13 Jan 1999 03:11:33 -0700
>Received: (from slist-at-localhost)
>	by pupman.pupman-dot-com (8.8.5/8.8.5) id WAA31088;
>	Tue, 12 Jan 1999 22:11:53 -0700
>Resent-Date: Tue, 12 Jan 1999 22:00:19 -0700
>Message-Id: <>
>Approved: twf-at-verinet-dot-com
>X-Sender: twf-at-verinet-dot-com
>X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.6 (32)
>Date: Tue, 12 Jan 1999 18:50:47 -0700
>To: tesla-at-pupman-dot-com
>Subject: Re: HV supply regulation
>Mime-Version: 1.0
>Content-Type: text/plain; charset="us-ascii"
>Resent-Message-ID: <"OiAjc3.0.t95.ZX2ds"-at-poodle.pupman-dot-com>
>Resent-From: tesla-at-pupman-dot-com
>X-Mailing-List: <tesla-at-pupman-dot-com> archive/latest/283
>X-Loop: tesla-at-pupman-dot-com
>Resent-Sender: tesla-request-at-pupman-dot-com
>From: Tesla List <tesla-at-pupman-dot-com>
>Original Poster: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com> 
>Tesla List wrote:
>> Original Poster: "rwall" <rwall-at-gateway-dot-net>
>> 1/10/99
>> Greg,
>> Would you go more into detail on high voltage DC active regulation?  
I am
>> building a 7 kV 1.0 A DC power supply with a bridge made of four 872A
>> rectifier tubes.  I am going to use big chokes and big filter caps 
>> regulation.  How can this power supply be actively regulated to say 
>> RWW
>> ----------
>> > Avoid the big DC filter cap if at all possible.
>> > If you really need 1% stability, active regulation
>> > is far simpler, and more accurate.
>> > --
>> >
>> >
>> > -GL
>> > www.lod-dot-org
>> >
>You could consider a hard tube shunt regulator scheme exactly like they
>used in the old color TV sets.  Here they employed a 6BK4 HV triode. 
>The cathode was basically tied to supply ground (neg)with a series
>resistor to establish cathode bias and the plate went directly to the 
>positive load terminal.  A dropping resistor was either employed 
>the load(CRT ultor)/shunt regulator and the supply, or the supply was 
>sufficiently high impedance that they didn't bother (you will 
>have to employ one).  A restive divider stack sampled the high voltage
>and a low end tap (actually a voltage set pot in series with the bottom
>of the divider) drove the control grid of the shunt regulator triode. 
>If the high voltage across the load went more positive, the shunt
>regulator grid would be driven more positive (or less negative
>referenced the cathode) and the tube would conduct more heavily, 
>more drag on the HV supply and lowering the voltage.
>I think you could do a big version of this using a transmitting triode
>tube like perhaps a 3CX10000D, or a tetrode like the 4CX10000D.  These
>tubes will handle up to 3 amps on the plate at up to 7500 volts.  
>I would expect the tetrode might be better because the control grid has
>much higher gain (you want a sharp cutoff tube).  You might best supply
>the screen from a resistive divider to ground from the tube's plate
>What you would in effect be doing is achieving regulation by employing 
>"smart load".
>Robert W. Stephens
>Who likes big toobz

Get Your Private, Free Email at http://www.hotmail-dot-com