Win's next 10kV project, a 1us ramp

[Winfield Hill]

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

 

[Jim Thompson]

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

Piece-a-cake ;-)

...Jim Thompson

 

[John Larkin]

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

Does the slope have to be continuously variable? What's the rep-rate?
What's the load? What's the polarity? Got any hydrogen thyratrons in
stock?

And, of course, what's it for?

John

 

[Spehro Pefhany]

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

What's the load look like?


Best regards,
Spehro Pefhany

 

[Joerg]

Hello Win,

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

Is it going to be a stack of FETs? Or can you use a tube?

Regards, Joerg

 

[Bob]

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

I hope you've had all the kids you ever intend to.

Be careful!

Bob

 

[John Larkin]

Hello Win,


Is it going to be a stack of FETs? Or can you use a tube?

MIT RadLab, volume 5, "Pulse Generators."


John

 

[[email protected]]

What's the load look like?


Best regards,
Spehro Pefhany

How much current? I know this more or less the same question, but
that's the answer the peanut gallery needs ... Jim Thompson's
piece-of-cake would start to look a bit rash with loads above 1nF,
which would need currents above 10A.

 

[Frank Bemelman]

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

In Dutch, "ramp" means disaster. I'm still on the internet,
so it hasn't happened yet. Sheesh, 9:23 AM and trying to
be funny already

 

[Robert Baer]

Over the years I've completed a number of projects involving
roughly 10kV voltages: fixed sources, fast-shutoff, reversible
programmable DC sources, precision-ramped AC sources at 300kHz
to 1MHz with 10kV maximum amplitude, etc.

Now I'm challenged with a creating a moderately-precise (5%),
programmable, fairly-fast 10kV ramp, of 1 to 50us in duration.
It's floating on 3kV. The 1us-long, 3kV to 13kV ramp spec is
tough, but may have a relaxed 5%-precision spec, provided it's
repeatable.

Question given as a possible solution:
Would it be acceptable to use a flyback transformer to add that
waveform to a DC supply?

 

[Tony Williams]

In Dutch, "ramp" means disaster. I'm still on the internet,
so it hasn't happened yet. Sheesh, 9:23 AM and trying to
be funny already

Microsoft security patch for the .wmf thing automatically
came in early this morning.

 

[Tim Williams]

Question given as a possible solution:
Would it be acceptable to use a flyback transformer to add that
waveform to a DC supply?

Hmm, I don't think the slope would be particularly accurate, though. Might
could try an old technique of pulse regulating, or whatever it was called...
it was used in tube color TVs. You use a chunky tetrode to switch the
flyback, then a low perveance triode to load down the flyback pulse. This
was used to indirectly regulate the high voltage supply for the CRT. Of
course you need live feedback to control the rising slope or else do it with
open loop correction, which would just make things trickier.

Huh. Hey Win, what's wrong with a big assed cathode follower? ;-)

Tim

 

[[email protected]]

Whats the rep rate? Can you have some jitter at the low or high end?
How much current?

I spend two days a week working in a lab that uses electrostatics. Its
probably not fast enough or controllable for yout task, but when my
boss asked for a fast 30Kv ramp, I ripped a vacuum relay out of a
defibrillator , and got in a heck of a lot of trouble with the legal,
purchasing, and safety offices for buying a unauthorized, uncertified,
and used defib. But thats the easy way to get a decent vacuum relay
these days without ordering a whole production run. To get it
shipped I had the surplus company keep the paddles, that made the
autocrats happy.

We have another commercial box made by the company that makes our HV
supplies (Gamma High Voltage Inc.) that uses a color shunt TV triode
acting as a switch up to 30KV, and to get a ramp we hang a RC off it.
However no supply in our lab goes higher then 2 mA, so it may not meet
your needs.

Steve Roberts

 

[Winfield Hill]

Spehro Pefhany wrote...

What's the load look like?

Not too bad, it's a 10pF electrode inside a vacuum chamber.
Add another 30 to 50pF for a connector and some cable. Add
the self-capacitance of a switch/amplifier/inductor/etc., and
come up with a 0.5 to 1A charging current to move 10kV in 1us.

 

[John Larkin]

Hmm, I don't think the slope would be particularly accurate, though. Might
could try an old technique of pulse regulating, or whatever it was called...
it was used in tube color TVs. You use a chunky tetrode to switch the
flyback, then a low perveance triode to load down the flyback pulse. This
was used to indirectly regulate the high voltage supply for the CRT. Of
course you need live feedback to control the rising slope or else do it with
open loop correction, which would just make things trickier.

Huh. Hey Win, what's wrong with a big assed cathode follower? ;-)

Or a 1-tube Miller rundown thing.

John

 

[Winfield Hill]

John Larkin wrote...

Tim Williams wrote...


Or a 1-tube Miller rundown thing.

Are there any practical 12 to 15kV triodes, or pentodes?

 

[Tim Williams]

Are there any practical 12 to 15kV triodes, or pentodes?

Plenty, though none off the top of my head. *Peruses ARRL Handbook*
4-1000A? 6kV max. plate, not quite enough although that's probably for
transformer output, so peak would be in the 12kV range, same as your
application.

Wait, "practical" triodes? Are you pulling my leg? ;-)

Tim

 

[Kevin White]

John Larkin wrote...

Are there any practical 12 to 15kV triodes, or pentodes?

Win,

EHT shunt regulators as used in old colour televisions may still be
available and meet your needs. e.g. 6BD4 They would only have low
heater cathode insulation so would need a floating supply for that.

http://tubedata.tigahost.com/tubedata/sheets62.html

kevin

 

[John Larkin]

John Larkin wrote...

Are there any practical 12 to 15kV triodes, or pentodes?

Hard-tube radar modulators did tens of amps at voltages like 20K, with
pulse widths in the 1 us range. Check RadLab volume 5 for circuits.

I was thinking about a classic glass jug like an 833A or something.
Anybody know how much plate current one of these can manage? My
transmitting tube books are at home.

There is a smallish tetrode (I think) that was used in HV power
supplies, Kepco and such... got one around here somewhere. And of
course the 6BK4, 25 kilovolt shunt regulator used in old color TV
sets, but it wouldn't sink enough current for you.

John

 

[Joerg]

Hello John,

MIT RadLab, volume 5, "Pulse Generators."

Is that available online? I could only see literature on scholar.google
that quoted RadLab.

Anyway, I was thinking about those ballast triodes in earlier color TVs.
If there is any chance to find one, that is, without having to rent a
backhoe and dig through a landfill.

Regards, Joerg