25kV AC

 We need a 25kV rms AC signal.  OK, that's 70kV p-p. 

 I had a 30kV Trek model 678 amplifier, a huge beast
 procured on eBay, but I fear it was thrown away in
 a downsizing move, damn!  With that we could make a
 10kV rms AC signal, at a frequency of our choice. 
 And maybe transform it up to 25kV.

 Years ago I made RIS-333 / RIS-470, a 10kV 600kHz
 amplifier / resonant-transformer for a mass spec. 
 That was 10kV amplitude, or 20kV p-p.  RIS-480 /
 RIS-514 was a compact 7.5kV 300kHz version.  But now
 we need more voltage, and at much lower frequencies.

 A company, Transzvill, in Budapest, sells the FM-24.
 It's a huge 300x363mm AC-line transformer, rated at
 24kV 400VA.  I think it's molded, rather than oil-
 filled.  OK, at least it's not a pole-pig.  But,
 haha, we only need 10uA of current, so something
 much smaller would be nice.

 50 or 60Hz are probably good frequencies for us,
 although it'd be nice to experiment with a little
 bit higher, maybe 400Hz.  Hmm, many 60Hz power
 transformer are happy at 400Hz.  Use a class-D
 amplifier to drive a 50-to-230V step-up xformer,
 then on to a 25kV transformer beast someplace.

 I have all types of small high-voltage pulsers /
 transformers, many from Alibaba, for electrostatic
 precipitators, etc.  Some are sold simply to make
 sparks, but these are short-duration pulse types,
 and we need 2-10ms pulses, too long.  TV flyback,
 15kHz, nah.  Also, Tesla-coil types need not apply.  

 Ah, maybe a neon-sign transformer of some type.
 Hmm, only 10 to 15kV.  And most are big and bulky.


-- 
 Thanks,
    - Win

Winfield Hill wrote:

>   We need a 25kV rms AC signal.  OK, that's 70kV p-p.

~100 small 230V/12V transformers with primaries connected
in series should do the job. This is 10x10 grid of them,
doable and reasonably compact.

	Best regards, Piotr

Winfield Hill <winfieldhill@yahoo.com> wrote in 
news:qmsfbm02m7s@drn.newsguy.com:

>  We need a 25kV rms AC signal.  OK, that's 70kV p-p. 
> 

<https://www.advancedenergy.com/products/high-voltage-power-supplies/>

Winfield Hill <winfieldhill@yahoo.com> wrote in 
news:qmsfbm02m7s@drn.newsguy.com:

>  We need a 25kV rms AC signal.  OK, that's 70kV p-p. 
> 
snip

<https://www.advancedenergy.com/products/high-voltage-power-supplies/x-
ray-power-supplies/xrg70-series/>


  70kV right on the button.

On Monday, September 30, 2019 at 4:45:49 AM UTC-4, Winfield Hill wrote:
> We need a 25kV rms AC signal.  OK, that's 70kV p-p. 

>  Ah, maybe a neon-sign transformer of some type.
>  Hmm, only 10 to 15kV.  And most are big and bulky.

Try the ignition coil from a 4 cylinder wasted spark engine. There are two transformers inside with the ends isolated that go to the spark plugs. The coils are driven separately and use the flyback energy to develop the high voltage. You can probably put the coils in series to double the output voltage.  The transformers are cheap, readily available, and small and light.

So if you can use pulses instead of a sine wave, this may be your ticket.


>  Thanks,
>     - Win

Steve Wilson wrote...
>
>On Monday, September 30, 2019 at 4:45:49 AM UTC-4, Winfield Hill wrote:
>> We need a 25kV rms AC signal.  OK, that's 70kV p-p.=20
>
>>  Ah, maybe a neon-sign transformer of some type.
>>  Hmm, only 10 to 15kV.  And most are big and bulky.
>
> Try the ignition coil from a 4 cylinder wasted spark engine. ...
>
> So if you can use pulses instead of a sine wave, this may
> be your ticket.

 Thanks, but they'd need to be able to make 5ms pulses,
 that's ms, not us.


-- 
 Thanks,
    - Win

DecadentLinuxUserNumeroUno@decadence.org wrote...
>
>Winfield Hill <winfieldhill@yahoo.com> wrote in 
>news:qmsfbm02m7s@drn.newsguy.com:
>
>>  We need a 25kV rms AC signal.  OK, that's 70kV p-p. 
>
><https://www.advancedenergy.com/products/high-voltage-power-supplies/>

 Yep, nice stuff, lots of stuff, but all DC not AC.


-- 
 Thanks,
    - Win

Piotr Wyderski wrote...
>
>Winfield Hill wrote:
>
>>   We need a 25kV rms AC signal.  OK, that's 70kV p-p.
>
> ~100 small 230V/12V transformers with primaries connected
> in series should do the job. This is 10x10 grid of them,
> doable and reasonably compact.

 Whoa!!  Huge arcs from secondary to primary
 destroys the transformers, sorry.


-- 
 Thanks,
    - Win

On Monday, 30 September 2019 11:23:49 UTC+1, Winfield Hill  wrote:
> Piotr Wyderski wrote...
> >Winfield Hill wrote:

> >>   We need a 25kV rms AC signal.  OK, that's 70kV p-p.
> >
> > ~100 small 230V/12V transformers with primaries connected
> > in series should do the job. This is 10x10 grid of them,
> > doable and reasonably compact.
> 
>  Whoa!!  Huge arcs from secondary to primary
>  destroys the transformers, sorry.

The driver circuitry would be a real trip, with the transformers having no chance of withstanding 25kV. Maybe repalce each of those 100 transformers with a series of 25 of them, with high Rs to equalise V drop :)

I don't know of anything ready made, it's custom time. Early TV EHT transformers produced a few kilovolts at piddlyamps from mains. Such supplies were a real hazard.

If you didn't give a whatsit about the waveform & only wanted it briefly for testing I daresay you could produce dc & use motorised contacts to make ac. Crude would be the word. Enjoy the ozone.


NT

On Monday, September 30, 2019 at 6:22:07 AM UTC-4, Winfield Hill wrote:
> Steve Wilson wrote...

> > Try the ignition coil from a 4 cylinder wasted spark engine. ...

> > So if you can use pulses instead of a sine wave, this may
> > be your ticket.
 
>  Thanks, but they'd need to be able to make 5ms pulses,
>  that's ms, not us.

Hmm... What would happen if you put a 1 nf cap across the secondary? Probably ring, but at what voltage?
 
> 
> -- 
>  Thanks,
>     - Win