25kV AC

[Winfield Hill]

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 <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.

 

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/>

 

[Piotr Wyderski]

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]

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

 

[Winfield Hill]

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

 

[Winfield Hill]

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

 

[Steve Wilson]

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

 

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

 

[Steve Wilson]

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

 

[Jeroen Belleman]

Winfield Hill wrote:

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.

Win, I don't see how you can expect to get by with 10uA.
Parasitic capacitances alone will take more than that!

What's this for?

Jeroen Belleman

 

[Tim Williams]

Two CRT flybacks + pair 6BK4C + HV optos to drive them (since Vgk ~ 100V).
:^)

One flyback needs to be heavily isolated, suggest LEDs + PV for expedient
isolation; otherwise, a custom resonant transformer will do.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

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

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

 

[Bill Sloman]

On Monday, September 30, 2019 at 6:45:49 PM UTC+10, Winfield Hill wrote:

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.

My thought would be an extended ferrite core - made up of perhaps two of these sets, with the two U-sections separated by the two I-sections - to make a toroid with enough space in the middle to make room for a useful number of turns of 25kV-capable cable.

http://www.farnell.com/datasheets/2138476.pdf

You could extend it further with more I-sections

http://www.farnell.com/datasheets/1595819.pdf

None of them are cheap.

25kV for 5msec is a lot of volt-seconds. Even with gaps, you might end up needing a very long path through the ferrite to avoid saturation.

It might give you a way of setting up Piotr Wyderski's array of lots of transformers with enough room for cables that wouldn't arc through.

--
Bill Sloman, Sydney

 

[John Robertson]

On 2019/09/30 7:05 a.m., Winfield Hill wrote:

Tim Williams wrote...

Two CRT flybacks + pair 6BK4C + HV optos to drive them
(since Vgk ~ 100V). :^)

Flyback plus HV diode, one each for pos and neg
pulsing, into a 35kV cap, make a 25kV square wave?
But we also do need some time at zero volts.

B&W TVs used ~15KV flybacks running around 15,756KC and were AC output
until the HV diode which was external in many cases.

Is the frequency a problem? If not then as suggested use a colour TV
flyback and cut open the shell to remove the HV diodes and that will
probably work. Flybacks are in the uA range, and I assume you aren't
looking for any current here.

A single flyback would then suffice. Still available from sources such as:

https://www.goldmine-elec-products.com/

Possibly

http://www.surplussales.com

I have a small pile of colour TV flybacks from both projectors and TVs -
any one of which will likely work.

John :-#)#

 

[Winfield Hill]

Jeroen Belleman wrote...

Winfield Hill wrote:
DecadentLinuxUserNumeroUno@decadence.org wrote...
Winfield Hill <winfieldhill@yahoo.com> wrote:

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.

Win, I don't see how you can expect to get by with 10uA.
Parasitic capacitances alone will take more than that!

What's this for?

This is for AC-driven electrospinning. OK, at 60Hz,
with 100pF wiring, the AC load is j26 M-ohms, making
an AC current of about 1mA. At 400Hz it'd be 6.3mA,
consuming 157 watts if in phase. OK, that's a point.
Maybe a 400VA transformer isn't overkill after all.


--
Thanks,
- Win

 

[Winfield Hill]

Tim Williams wrote...

Two CRT flybacks + pair 6BK4C + HV optos to drive them
(since Vgk ~ 100V). :^)

Flyback plus HV diode, one each for pos and neg
pulsing, into a 35kV cap, make a 25kV square wave?
But we also do need some time at zero volts.


--
Thanks,
- Win

 

[Winfield Hill]

Wond wrote...

The old oil-furnace ignition transformers would initiate
and sustain an arc about an inch and a half long, in air.
Dunno what voltage.

Yes, interesting, and much smaller. Probably too low a
voltage. Also, we need hours of continuous operation.


--
Thanks,
- Win

 

[Tauno Voipio]

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.

--

-TV

 

[Winfield Hill]

jlarkin@highlandsniptechnology.com wrote...

Win, can you use differential drive into your gadget?
Maybe a full-bridge with the uppers just constant-current,
so the lower grids are near ground.

I'd go with a 35kV full-bridge, with each leg using
35 1.2kV MOSFETs in series, with a 4x.26-type gate
divider. I'm using IXTY02N120P, low-capacitance
DPak parts, with a 70-piece minimum order, I just
received 140 of them. Machine assembly.

Nah, just buy a big transformer!


--
Thanks,
- Win

 

[Wond]

On Mon, 30 Sep 2019 01:45:42 -0700, Winfield Hill wrote:

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.

The old oil-furnace ignition transformers would initiate and sustain
an arc about an inch and a half long, in air. Dunno what voltage.