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
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>Subject: Re: HV supply regulation
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>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>
>> Would you go more into detail on high voltage DC active regulation?
>> 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
>> > 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
>Robert W. Stephens
>Who likes big toobz
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