Hi,
I've just started an Associates level Biomedical Engineering Technology program and we have to design a power this semester in Multisim for my Electronics class and I also have to design on paper an X-Ray machine for my Rad Physics course. I would like to actually build a power supply that can produce volts that range from 1000 V to
60000 V. For starters, what type of chassis should I use?Thanx, Ed
Red.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Metal, probably. Big.
John
Color TV Chassis !
Add a Second Voltage Doubler for 30-60 KV !
TV's are limited to ~ 25 KV to prevent Higher Energy X-Ray generation !
Using a TV High Voltage stage makes lots of sense, and the current range is about right too !
You would have to solve a 30 KV capacitor problem, maybe use an old Picture Tube ?
You wouldn't have to obtain a high Voltage Transformer.
Crockroft-Walton ? circuit comes to mind. Yukio Yano
This is totally off topic, but Yukio are you Japanese? ???????????????
Mike
Bakelite is actually not a good choise. The problem is that it "tracks". If you get some leakage across the surface (say because it's dirty) the surface turns to carbon. That carbon conducts slightly which draws more current which makes more carbon... It spirals downhill fast.
I'd use a metal chassis with ceramic standoffs.
-- These are my opinions, not necessarily my employer's. I hate spam.
Well for one thing, a 15kV supply can fit six in a pack of cigarettes for a mere 20uA requisite.
For mA levels or more even, one needs a bit more kick in your get-along.
You would not want a supply that can be adjusted over such a large range either.
You want one that makes 1000V at up to a few mA to a few tens of mA.
For the X-ray supply, it depends on the tube size. I have seen everything from gas pipe X-ray supplies that are a mere 4kV at 1mA and
0.000006% ripple, and I have seen 50kV @ 200mA for a supply we made for LANL to peer into nuke casings.You need to define your power requisites, then you can have a clue as to how big your output transformer that pumps your multiplier stage needs to be, etc.
A supply that runs the gamut from 1kV to 60kV and a mA or so to the needs a 60kV driven X-ray tube would need is just not very feasible.
To get a 60kV X-ray supply from TV anode supplies, take two. One at
+30kV, and one at -30kV. X-ray tube gets driven at 60kV, and the radiation of the supplies remains low.
If you're gonna be changing the supply, you'll start with a small tank of insulating oil (like, 50 gallons of Diala AX or somesuch). Air is rotten insulation at 10 kV and above, so one either uses potting compound like a TV supply, or a vat of oil. Potting the circuit would make it hard to change, so... oil.
As to the rest, 1000 to 60,000 is a wide range; without knowing the current requirement, it might be a little motor-driven Van de Graaf or a switchmode power supply with Cockroft-Walton rectifiers.
50 gallons of specialized transformer oil will be costly.
Cheaper, and much more serviceable to get a gallon of fluorinert:
It will allow one to place un-potted supply stages under power safely, and without the oily mess.
1500 V per mil dielectric strength.
This is definitely not a beginners project. 60kV will arc over enough distance to kill very easily. Real products that I have worked on use either teflon, vacuum, or about 1 foot of air as the insulator. Also much mechanical construction with just the right materials. So that when they do fail, which does happen occassionaly like when the output gets shorted, an arc doesn't jump through the controls and take you out with it. Your best bet would be to go and take a look inside some pre-existing boxes and get some service manuals and have a good long read. You will need more than 5 minutes on Google to get a safe result.
regards Andrew
RIGHT. How do you propose that two be cascaded, dim bulb?
-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
They don't get cascaded, dumb f*ck.
They are both full floaters, and you tie the negative lead of one to the positive lead of the other and ground that node. Then, you have a plus 30kV supply and a minus 30kV supply wrt ground. The x-ray tube is a full floater, so the +30kV and the -30kV fed into it yields 60kV at the target.
The last X-ray supply I made was two 90kV supplies set up in this exact manner, and it fed a Palladium target (about 20 grams) $900 X-ray tube at
180kV. It was all set into a steel cased lead lined box with oil, and an expansion tank, and the whole thing weighed over 150Lbs, and that was without the front end driver/control supply. It was not a flyback method driver either. I've got pictures here somewhere I can post in abse.That is the supply/X-ray source that is under the conveyor at your local airport, looking at your carry on luggage.
So f*ck you.
You don't know anything about second anode supplies then. They are cast in epoxy, and not designed to float.
The only 'floater' was the defective condom your dad used. You are as ignorant of TV power supplies as you are about most things, dim bulb.
You just admitted that you're shooting blanks, as usual.
No thanks. I prefer a woman, and human. BTW, congratulations on having a new strain of VD named after you.
-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.