Power supply topology for 150kV

[BootstrapBill]

I'm going to be building a 30kW, 150kV supply. I want to be able to control it from 50kV to 150kV. This is for an x-ray tube and current will be controlled by filament current. There will be be a sense resistor to monitor current and trip circuit if their is a spike.

I've mostly seen resonant converters as they work well with multipliers. I like this topology but the control and sense circuitry are complex. I have also seen transformers with their secondaries in series. This topology would be hard to isolate HV from primary.

I had a mag company give me a ferrite core/winding suggestion for a 340 pri/15kV sec. I want to go from a half/full bridge to the step up transformer to a multiplier stage. I would like to use something simple like pwm to control voltage but I can't seem to come up with a topology because of the multiplier after the secondary.

Is there a simple hard switching converter topology that could accomplish my goal?

Thanks

[CM800]

I'm going to be building a 30kW, 150kV supply. I want to be able to control it from 50kV to 150kV. This is for an x-ray tube and current will be controlled by filament current. There will be be a sense resistor to monitor current and trip circuit if their is a spike.

I've mostly seen resonant converters as they work well with multipliers. I like this topology but the control and sense circuitry are complex. I have also seen transformers with their secondaries in series. This topology would be hard to isolate HV from primary.

I had a mag company give me a ferrite core/winding suggestion for a 340 pri/15kV sec. I want to go from a half/full bridge to the step up transformer to a multiplier stage. I would like to use something simple like pwm to control voltage but I can't seem to come up with a topology because of the multiplier after the secondary.

Is there a simple hard switching converter topology that could accomplish my goal?

Thanks

Sounds like you just want a high power full-bridge, resonant may be more efficient. You are really scaling up a small SMPS to large scale, you'd just use brick IGBTs rather then TO-220 and independent gate-drivers, possibly coupled, very likely with protection on them.

http://www.stevehv.4hv.org/ccps1.htm
http://uzzors2k.4hv.org/index.php?page=slrconverter
http://uzzors2k.4hv.org/index.php?page=multiinverter

Naturally these are hobbiest projects, you will want to add a lot of protection & Safety circuits on them, along with reliability etc.

[BootstrapBill]

I already have single brick IGBTS(300A, 1200V). I'm probably going to use 3120 optos to drive gates of mosfets that will then power gate drive transformers (I don't know of anything else that can drive the brick IGBT gates). I'm just not very familiar with control circuits for Resonant converters. All the x-ray supply scholarly articles are series-parallel-series topoligies focusing on efficiency. I like the idea of the fixed frequency rescon. Thanks for the links

[CM800]

I already have single brick IGBTS(300A, 1200V). I'm probably going to use 3120 optos to drive gates of mosfets that will then power gate drive transformers (I don't know of anything else that can drive the brick IGBT gates). I'm just not very familiar with control circuits for Resonant converters. All the x-ray supply scholarly articles are series-parallel-series topoligies focusing on efficiency. I like the idea of the fixed frequency rescon. Thanks for the links

You're going to want to work out what frequency your IGBTs can handle and then design the transformer to operate at a suitable frequency. As a hint, most XRTs run at 20kHz.
I would suggest reading all the application notes you can find, expecially from AVAGO, Fairchild, IXYS. IXYS and AVAGO expecially.

Honestly I'd recommend just buying an x-ray transformer and driver, 50Hz is best, then set up a rectifier with vacuum tubes, the xrt may or may not already have one.

Contact x-ray machine installers, medical equipment servicemen etc. It's best to visit in person, offer beer and PAY BY CASH (off the books, everyone likes tax - free beer money)

[BootstrapBill]

Thanks for advise. I'm a medical equipment serviceman haha. There is no x-ray equipment I know of that delivers that kind of power except CT scanner generators. They are all so involved with the rest of the system to ensure patient dose safety that it would be easier to find the space for a whole CT scanner than to trick the control circuitry into working.

[Lightages]

Please be careful with this. This WILL KILL YOU if you do the wrong thing. I always get afraid when people ask questions online about VERY dangerous things. If you need to ask on a forum how to do something, then it makes me think you have never had experience or had someone show you the correct safety procedures.

[Alex Eisenhut]

This is even beyond the machines they use to X-ray welds and NDT stuff.

http://www.balteau.com/products.php?type=56

Are you trying to create a Therac-25 for the 21st century?

[BootstrapBill]

I think that would be a Probeam.. slightly more voltage required

[T3sl4co1l]

Or a particle collider Marx generator...
 

Tim

[tggzzz]

Please be careful with this. This WILL KILL YOU if you do the wrong thing. I always get afraid when people ask questions online about VERY dangerous things. If you need to ask on a forum how to do something, then it makes me think you have never had experience or had someone show you the correct safety procedures.

Just to amplify that. There are several ways that it could kill/maim you, some instantaneous, some much slower.

[CM800]

Please be careful with this. This WILL KILL YOU if you do the wrong thing. I always get afraid when people ask questions online about VERY dangerous things. If you need to ask on a forum how to do something, then it makes me think you have never had experience or had someone show you the correct safety procedures.

Just to amplify that. There are several ways that it could kill/maim you, some instantaneous, some much slower.

A few points on keeping safe:

-Duel deadmans switch (you find these on robot arms, if you release it goes into emergency stop, it also goes into e-stop if you push too hard) This is important as the currents involved could equally force you to press down very hard on it, or release it.

-Fiber optic / air switch everything. Keep your distance, use a non-conductive method of control, fiber is best IMHO.

-Cover your Powered components, detonating IGBTs can shoot out bits of copper and shards of fiber re-enforced plastic / epoxy, this will happily take your eye out, it will also happily cut into your neck...

-Test / develop with a low voltage transformer. Get your transformer manufacturer to wind you a unit with less turns, say 100V output, you can then dump this into a massive resistor bank or salt pool as a constant load, this will allow you to test and measure much safely.

-Equipment. You NEED differential probes and current probes, if you don't have these, just stop right there.

[mk_]

I'm going to be building a 30kW, 150kV supply. I want to be able to control it from 50kV to 150kV. This is for an x-ray tube and current will be controlled by filament current. There will be be a sense resistor to monitor current and trip circuit if their is a spike.

I had a mag company give me a ferrite core/winding suggestion for a 340 pri/15kV sec. I want to go from a half/full bridge to the step up transformer to a multiplier stage. I would like to use something simple like pwm to control voltage but I can't seem to come up with a topology because of the multiplier after the secondary.

Is there a simple hard switching converter topology that could accomplish my goal?

Thanks

Take a look at phaseshift-Controllers (full bridge on primary side is more or less easy, even if you have to handle more then 100A at full power)....  a well dimensoned inductor on secondary side reduceds current peaks in the Rectifier/Multiplier.


Feedback from the high-Voltage side could be funny, specialy if you need high bandwith for your regulation... (you must do pulse per pulse regulation on your primary side, so oscillation is not far away)

And now something you din`t ask but should be said:

Anyway - the most critical and expensive investment is all that equipment you need for your security (Variable transformer for variable voltage @ primary power in, you will not power up your first testsystem with full voltage) including some emerengy shutdownbuttons, a partner in the lab who knows how to react if something blows up (never, never, never be alone in the lab when running with power), cooling-equipment, a load were you can dump your 150kV@30kW.... Protectionglasses for your eyes which don`t break if something blows violently up, ear protection you can wear a long time comfortly (it is really loud if something goes booom)

Not to forget a scope with a lot of channels (4 are not very much for such a task when studying feedbackloops or Vce_sat on an IGBT ), reliable Currentprobes, Differential probes for low voltage (you can`t measure low voltage stuff if 100A and 500V rising within 50ns from 0 to 500V are roaring some 3cm away) and also some very high voltage differential  probes with specified voltage at required bandwith for secondary side.

But beside that: it is great fun and I like my work doing this on a regular base...

btw: at the eth zürich you can find a lot of great papers about that stuff... PM if urls required

Good luck

mk_

[BootstrapBill]

I really do appreciate all the safety recommendations.. can never be too safe. To make you feel a little better I have been working with high voltage equipment for over 10 years and know the industry safety standards.

I have a 4kW 60kV generator already in use. The room is lead shielded and x-ray is wirelessly controlled.

I had planned on starting out low rail voltage, a step down transformer, and a resistive load. I would then work up to adding a few multiplier stages, then upping the turns ratio, etc.

This is also going to be properly built. It will appear to be a commercial product. Everything will be properly isolated and in dielectric oil. 

[Fungus]

Please be careful with this. This WILL KILL YOU if you do the wrong thing. I always get afraid when people ask questions online about VERY dangerous things. If you need to ask on a forum how to do something, then it makes me think you have never had experience or had someone show you the correct safety procedures.

Just to amplify that. There are several ways that it could kill/maim you, some instantaneous, some much slower.

And that's just the voltage. Never mind the X-rays. 

A few points on keeping safe:
-Duel deadmans switch
-Fiber optic / air switch everything.
-Cover your Powered components, detonating IGBTs cank...
-Test / develop with a low voltage transformer.
-Equipment. You NEED differential probes and current probes

Most important: Record everything on hi-speed video for the coroners report and/or amusement of electrical engineers everywhere. Pay particular attention to lighting and microphone placement. Multiple camera angles would be appreciated.

[BootstrapBill]

Please be careful with this. This WILL KILL YOU if you do the wrong thing. I always get afraid when people ask questions online about VERY dangerous things. If you need to ask on a forum how to do something, then it makes me think you have never had experience or had someone show you the correct safety procedures.

Just to amplify that. There are several ways that it could kill/maim you, some instantaneous, some much slower.

And that's just the voltage. Never mind the X-rays. 

A few points on keeping safe:
-Duel deadmans switch
-Fiber optic / air switch everything.
-Cover your Powered components, detonating IGBTs cank...
-Test / develop with a low voltage transformer.
-Equipment. You NEED differential probes and current probes

Most important: Record everything on hi-speed video for the coroners report and/or amusement of electrical engineers everywhere. Pay particular attention to lighting and microphone placement. Multiple camera angles would be appreciated.

Will do. Video won't be too exciting.. there won't be anyone in the room.

[jbb]

Please be careful of your capacitor banks.  Someone died in my last workplace because of a still-charged capacitor.

I don't know a lot about high voltage (in the sense of > 30kV) supplies, but a lot of the papers, literature, marketing material and teardown videos I have seen tend to use a transformer plus voltage multiplier.  So they're probably right.  (Especially as this will reduce the insulation requirements of the transformer.)   Considering something like a classical Cockroft-Walton multiplier, it's clear that a classic constant frequency variable duty cycle control isn't going to work well.  You probably want to drive that with a resonant converter in the interests of achieving a high switching frequency (smaller equipment) without spewing EMI all over the place.  (Although if the HV side is in a metallic oil enclosure you'd probably be OK.)

However, achieving a 3:1 adjustment range of output voltage is asking a lot of a resonant design (also think about what beam current range you'll need).  I therefore suggest you deploy a variable-ratio DC/DC buck converter to feed power into a fixed-ratio resonant stage.

Also, you should think carefully about which end of the supply you're going to float as this will impact your entire insulation design.  I assume you also know where to look for the relevant oil-compatible components.

[Zero999]

What duty cycle do you need?

Producing 30kW pulses at 150kV is not that difficult but doing it continuously is.

Where are you getting the power from? Just a big transformer connected to 3 phase mains is probably the easiest solution. The AC output can be converted to DC with an old fashioned rectifier. To minimise ripple and harmonics, use a 12  or even an 18 pulse rectifier.

[Marco]

Why resonant for something boutique nowadays with stuff like TPH3207WS out there? Not even that expensive.

[varghese]

30KW is huge ..  I have handled few watts but upto 120KV ,  Ussual procedure is convert it to dc & then make it to PWM pulses with frequncy around 20kHz - 30KHz (will give you good control & reduce the size of transformer/capacitor ).. Then step up the volatge to 10KV /20KV using transformer .. then introduce it to 10 to 15 stage CW multiplier .. For  Testing Have a good HV probe ..   Have a good earthing connection ..  Hold a ground wire every time you come close to the setup ..  Always ground the setup before touching it .. Use Transformer oil & High voltage Epoxys for insulation/ heat ttransmission..  For 150KV , I think you need keep atleast 1.5 meter distance (incase you are not holding earth wire ).. No idea on X ray side

[BootstrapBill]

Duty cycle- I need 2 sec bursts with 5 seconds between or continuously for 60 sec at 10-15kW

Not sure on the power but it will be rectified and and be going to a huge cap with soft start.

[CM800]

Duty cycle- I need 2 sec bursts with 5 seconds between or continuously for 60 sec at 10-15kW

Not sure on the power but it will be rectified and and be going to a huge cap with soft start.

Starting to sound like you're making a death-ray here.

[Jay_Diddy_B]

Duty cycle- I need 2 sec bursts with 5 seconds between or continuously for 60 sec at 10-15kW

Not sure on the power but it will be rectified and be going to a huge cap with soft start.

What kind of X-ray tube are you planning on using? A typical medical X-ray tube is limited to around 1kW dissipation.

Here is a link to a reasonable X-tube:

https://www.varian.com/media/107301/browser

It has a maximum anode dissipation of 1.5kW, but this may be limited by the oil-filled housing. a B130 Housing is limited to about 250W average without a fan and 500W with a fan.

Link: https://www.varian.com/sites/default/files/resource_attachments/B-130HPDS.pdf


Tube are sized by the anode diameter. This is a 4" tube, there also 3" tubes and the odd 5" heavy tube.

Regards,

Jay_Diddy_B

[CM800]

Duty cycle- I need 2 sec bursts with 5 seconds between or continuously for 60 sec at 10-15kW

Not sure on the power but it will be rectified and be going to a huge cap with soft start.

What kind of X-ray tube are you planning on using? A typical medical X-ray tube is limited to around 1kW dissipation.

Here is a link to a reasonable X-tube:

https://www.varian.com/media/107301/browser

It has a maximum anode dissipation of 1.5kW, but this may be limited by the oil-filled housing. a B130 Housing is limited to about 250W average without a fan and 500W with a fan.

Link: https://www.varian.com/sites/default/files/resource_attachments/B-130HPDS.pdf


Tube are sized by the anode diameter. This is a 4" tube, there also 3" tubes and the odd 5" heavy tube.

Regards,

Jay_Diddy_B

I'm pretty curious about this too, in even the smaller machines, tubes have spinning anodes as the focal point of the anode can reach in excess of 2500*C, Is it going to be made of unobtanium?

[BootstrapBill]

http://www.dunlee.com/page/reevo240

Yeah its the size of a small engine.. that's just the tube in a dielectric housing. 100kW for this guy.. ever hear of a CT scanner?

[MagicSmoker]

This is the coolest project I've seen in awhile... then again, I don't get out much.

So, a CT scanner x-ray source that needs 100kW at 120kV. I don't have any direct experience with this sort of thing, but my understanding is that x-ray tubes are fairly benign loads, with the caveat that when used in a CT scanner they need pretty good regulation of their anode voltage and current to prevent density artifacts in the resulting image slices. That argues against using a 5+ stage multiplier, as regulation tends to decline with every stage and you need close to 1A of current (Cockcroft-Walton multipliers are usually used for less than 10mA of current). Thus, I would use appropriate construction techniques to allow for a 30-40kV secondary so that only a 3-4 stage multiplier is needed. This page has some useful information on selecting/sizing a multiplier: http://www.voltagemultipliers.com/html/multdesign.html.

One other thing to consider is that you really don't want a choke on the secondary side, as it will need to be designed to withstand the full secondary voltage as well, so a good topology to consider that isn't too hard to get working is a PWM'ed buck converter feeding a full bridge with the bridge switches running at a fixed 50% duty cycle. The late Abraham Pressman covers this topology at length in his book on switching power supply design.