Winfield Hill wrote:
> Bert Hickman wrote...
>>
>> I'd recommend using a small oil-immersed 60 Hz dental X-ray
>> transformer powered from an autotransformer.  The frequency
>> should be in the right ballpark, you can easily tweak the
>> output voltage, and the power level should be in the ballpark.
>> Larger X-ray transformers are also available on the surplus
>> market if you need higher power.
> 
>   Ah, dental X-ray transformer, awesome, thanks Bert!
>   Do you think I'll be stuck with using transformer oil?
>   Maybe with degreasing and vacuum degassing thrown in?
> 

Win, it does indeed need to be operated under mineral/transformer oil to 
prevent corona and tracking damage. If the transformer has been pulled 
out of the X-ray head and oil for any length of time, it should be fully 
re-submerged and vacuum degassed to remove entrapped air. Since you only 
need ~25 kVRMS, a variable autotransformer will allow you to easily 
reduce primary voltage for the desired output.

On a sunny day (Tue, 1 Oct 2019 09:30:28 -0700 (PDT)) it happened
sroberts6328@gmail.com wrote in
<443d29d7-c518-49e9-940a-1a2b99ec0503@googlegroups.com>:

>One thing I forgot to mention. Shunt regulators can give off low energy X-rays.
>Low Energy X-rays are not fun, as their tissue adsorption is very high. A 1/8th inch thickness  aluminum box was sufficient for
>our purposes. 
>
>Steve 

Yes, this was also a thing with KTV parallel stabilizers (PD500) at 25 kV
 https://www.radiomuseum.org/tubes/tube_pd500.html
a colleague of mine ran a set without the metal screening and get his face all burned red.

After a while the glass would turn a bluish color from the Xray radiation.
 https://www.youtube.com/watch?v=MooYX2RqJTs

Once had a bunch of these tubes...


See Also:

 
Review of Scientific Instruments 79, 093904 (2008); https://doi.org/10.1063/1.2981699 

Review of Scientific Instruments 80, 026106 (2009); https://doi.org/10.1063/1.3079688

While not related to your problem, it gives a good overview of what happens with closed loop control.

Steve

One thing I forgot to mention. Shunt regulators can give off low energy X-rays.
Low Energy X-rays are not fun, as their tissue adsorption is very high. A 1/8th inch thickness  aluminum box was sufficient for our purposes. 

Steve

tirsdag den 1. oktober 2019 kl. 10.58.03 UTC+2 skrev DecadentLinux...@decadence.org:
> Robert Baer <robertbaer@localnet.com> wrote in
> news:KZAkF.9594$O_.6196@fx39.iad: 
> 
> > DecadentLinuxUserNumeroUno@decadence.org wrote:
> >> whit3rd <whit3rd@gmail.com> wrote in
> >> news:22395bd0-b492-48aa-8713- e26daf08651d@googlegroups.com:
> >> 
> >>>
> >>> Well, 20-year-old auto coils did 40kV peak, so there's
> >>> at least SOME commercial units that can do the deed.
> >>>
> >> 
> >>    They did no such thing s they are NOT "transformers" in the
> >>    sense 
> >> we know of them.
> >> 
> >>    They rely 100% on the field collpase of a DC energization of
> >>    the 
> >> COIL that is curtailed by (the opening of) a switch.  That sudden
> >> field collapse is why the voltage is so high.  Running AC into
> >> the primary of a car coil does NOT provide the same 25kV that the
> >> coil makes when a set of points open on a big DC Standing field
> >> and it slams back in at a high slew rate.
> >> 
> >>    That is the entire principal on which a points operated DC
> >>    fired 
> >> car coil ignition works.  It even makes kV potentials on the
> >> primary when it happens.  That's why it needs a damping
> >> 'condenser'. 
> >> 
> >    Well, son, ya gots it ron / konfutzzled.
> 
>   You have already fucked up with this stupid shit.
> 
> >    The configuration is as follows: it is a transformer, with
> >    low-Z / 
> > relatively low number of turns primary and a high-z / large number
> > of turns secondary; common ground.
> 
>    Yeah...  I know what an ignition coil is, chump. (or is it pops?)
> 
> >    When the points close, the battery is connected to the primary
> >    and 
> > current increases until the points open
> 
>   Yeah...  That is exactly what I said.  Current reaches max very 
> fast though, so your "increases until opened" crap is well.... crap.
> 
>   THEN the points open.
> 
> > and the (NOT "damping") 
> > condenser across the points
> 
>   Never said it did.  It does not even get in the circuit until and 
> only WHILE the points are OPEN.  Otherwise it is shorted across the 
> closed points.  D'oh!    You are getting senile, pops.
> 
> > /or, usually/ from ground to primary
> > high end then resonates,as in a standard flyback system.
> 
>   A flyback is a TV anode transformer.  An old points based 
> automobile ignition coil and circuit is a different animal than a TV 
> flyback.  Still a transformer, still a primary and secondary.  No 
> diode string in a car coil though.

some ignition coils have diodes in series with the secondary

some claim it is to remove the risk of a spark when energizing the primary
other as a clever way to use a single coil for a four cylinder

https://www.hella.com/techworld/assets/images/10032328a.jpg

Also we used to use arrays of jets, either pressurized needle, or gravity cone, driven with 1 Gig ballast resistors off the same PSU.

How you get into tens of grams per minute is what I can't discuss.

Steve

Win,

Um, AC is the hard way to increase production, unless your in a certain Russian non-wovens factory where they run the whole plant off a big transformer. :-)

Start a Espin jet with the usual DC. Note the voltage where the Taylor cone ruptures and the jet starts. Note that you can decrease the HV until the jet starves for current, however they tend to make smaller fibers if you decrease the voltage a little Say 5-10% after starting.

Note if you really increase the voltage over the static start voltage, the Taylor cone nearly implodes with the impulse and starts the jet fast, but it is unstable.

This is where I mention the words "Grounded Grid Shunt Regulator" such as 6EN4, but I imagine some of the Russian Surplus ceramic RF triodes would work just as well, if you cant find a 6EN4.

Basically shunt the jet assembly to not quite ground. Makes a pulsed DC, that acts like AC.

This idea should be credited to Dominick Galluzzo at Gamma High Voltage who used to sell the fast shunt switch box as a made on demand product. We bought our HV PSUs from Dom, usually the dual PSU with +30Kv adjustable and -30KV adjustable, in the same box. As his PSUs have a good protection stage built in, they tended to withstand student and professor abuse such as shorting and arcing and low impedance loads for years.

Basically we used mechanical means to get around this. I used to have a Basic Stamp drive a simple servo swinging a fiberglass rod from one PSU pole to the other on the dual PSU as a means of testing reversing of the field. This would let us shoot high speed video of the process your thinking about. When your around 60KV, you like simple, robust, and cheap. You also isolate your measurement and control PCs with long plastic fiber optics, but that is another story.

I also tried various Kilovac HV relays and spinning disk DPDT switches.

But it is easier to do things mechanically.

As for increasing production:

You can do things like a spinning cup of polymer with a serrated edge. Centripetal force pushes the liquid to the edge, and the edge is fine toothed bandsaw blade. The fluid "climbs up" and launches from the sharp field at the tooth. You can get a lot of polymer into the air this way, but your collector drum needs to be above the cup and grossly overcharged.

The other technique I like for multiple jets involves naturally rough, thin, tungsten wires dipping into the polymer pool. Say six wires 30-60 cm long mounted between two 6 cm spinning disks on the same shaft.

Yet another technique involves one wire wound into a tight helix that dips into and out of a polymer solution pool along its long axis.

Steve

On Wednesday, October 2, 2019 at 12:00:40 AM UTC+10, DecadentLinux...@decadence.org wrote:
> Bill Sloman <bill.sloman@ieee.org> wrote in
> news:5f0807db-74fa-4aba-ba5d-2b34cc21f86c@googlegroups.com: 
> 
> > The field doesn't "collapse". It decreases fast enough to induce a
> > rapidly increasing voltage across the  secondary, 
> 
>   Oh it full on collapses.  That is how the event gets generated.
> 
>   A sine wave is too soft to induce more than the standard step up 
> ratio offers.  A high slew rate event, however, steps into the realm of 
> infinity because the event is of near zero length.  Other physical 
> factors clamp that down, but that is the mechanism.  That high slew 
> rate (collapse) is the driving engine.

Do the math.

-- 
Bill Sloman, Sydney

Bill Sloman <bill.sloman@ieee.org> wrote in
news:5f0807db-74fa-4aba-ba5d-2b34cc21f86c@googlegroups.com: 

> The field doesn't "collapse". It decreases fast enough to induce a
> rapidly increasing voltage across the  secondary, 

  Oh it full on collapses.  That is how the even gets generated.

  A sine wave is too soft to induce more than the standard step up 
ratio offers.  A high slew rate event, however, steps into the realm of 
infinity because the event is of near zero length.  Other physical 
factors clamp that down, but that is the mechanism.  That high slew 
rate (collapse) is the driving engine.