25kV AC

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?


-- 
 Thanks,
    - Win

Michael Terrell <terrell.michael.a@gmail.com> wrote in
news:96d91df4-3bd0-44b7-8a20-3fa7bf26edb0@googlegroups.com: 

> On Monday, September 30, 2019 at 11:33:36 AM UTC-4, Tauno Voipio
> wrote: 
>> On 30.9.19 18:17, Winfield Hill wrote:
>> > Tauno Voipio wrote...
>> >>
>> >> The tens of kilovolts need careful attention to electric
>> >> field strength. The wires and terminals need to pretty
>> >> bulky to keep the field strength under control.
>> > 
>> >   Yes indeed.  We use a nice 4.8mm dia wire, AWM 3239,
>> >   with a 40kV rating, CSA TV-40.  Judd Flexrad HV.
>> 
>> 
>> Please be careful with radii of wire ends and terminations,
>> so that your kilovolts won't sizzle into thin air as corona.
> 
> 
>   Smooth, rounder solder joints are the rule for HV, instead of
>   the typical method of just enough solder for a good connection.
>   Some HV second anode wire was made to handle up to 40KV 
> 
> 

  I had to teach our assemblers how to make a solder joint insuring 
good wetting, and then make a round blob on it without sending it 
through the hole to the other side.  All the while making sure the 
multiplier diode or cap remained suspended above the PCB a bit, also 
an EIC QA fail.  But not for HV!

  Because it is hard to definitively QA the solder joint, one has to 
trust the assembler to have made good wetting and not just a dry blob 
joint. (after all they are so hard to light and get a good toke from)
Hehehe..  :-)

On Tuesday, October 1, 2019 at 7:10:50 PM UTC+10, DecadentLinux...@decadence.org wrote:
> Bill Sloman <bill.sloman@ieee.org> wrote in
> news:744aac08-c0ed-405b-8c79-f46f52ecee58@googlegroups.com: 
> 
> > It doesn't make kV potentials across the primary - the points
> > would have arced over if it had. 
> > 
> 
> Sure does.  Points DO arc.  That is why they have the condenser, 
> because if they did not metal transfer would occur and ruin the 
> points in short order.  That ONLY happens when an arc is present.
> 
>   So the points are closed and the coil fully energized for the 
> entire "dwell time", and when they open the bettery is OUT of the 
> circuit and the field collapses and the slew rate it slams down at 
> induces a high voltage in the secondary. 16 thousand times every 
> minute for a good average (v8).

The field doesn't "collapse". It decreases fast enough to induce a rapidly increasing voltage across the  secondary, and the changing voltage charges the interwinding capacitance of the secondary, which induces a current that largely compensates for the rapid decline of the current through the primary.

You can write out the equations for the process - which is a bit more helpful than saying that the field "collapses" though it does - initially - go down pretty fast.
 
>   Take your 100:1 ratio.   14 V in makes 140 V out.  NOT enough.

That's not what's going on.
 
>   So the collapsing flux field is the mechanism by which the 
> secondary snaps up to a high voltage

It doesn't "snap" up to a high voltage. It rises rapidly - at a rate set by the self-resonant frequency of the ignition coil. Calling it a "snap up" is unrealistic, and rather unhelpful.

> and the plug gap fires on the 
> secondary side and the point gap fires on the primary.  The primary 
> side gets the condenser because it keeps the points from eating each 
> other up.
> 
>   That is what the coil gets.  Regular system voltage.  So I said 14V 
> as a good number.

The 14v sets the current through the primary of the ignition coil, and it sets the starting point for the voltage rise after the points have opened.

You would see about 140V across the secondary of the ignition coil when the current first started ramping up, but it drops as the current rises and the resistance of the primary starts limiting the current.

It's irrelevant after the points have opened.

-- 
Bill Sloman, Sydney

DecadentLinuxUserNumeroUno@decadence.org wrote in news:qmvjk3$507$1
@gioia.aioe.org:

>  EIC 

errr...  IPC

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.

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

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  

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  

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

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