Xray transformer mods

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Ameen Aydan
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Xray transformer mods

Post by Ameen Aydan » Tue Jun 09, 2020 7:39 am

Hi all,

I got my hands on an xray transformer about a year ago now and I'm confident that it is fusor friendly but I've run into some trouble trying to figure out how to rewire this transformer. Here is a photo of the specs:
20181229_212306.jpeg
Transformer specs.
The transformer is rated for 300ma at 125kvp (tube voltage), it shouldn't have a problem running a fusor.

After I untanked the whole mess, it sat in my garage for about 9 months. I didn't have the time or effort to even touch it till this whole pandemic came into play. I know that I have to worry about the moisture seeping in but I don't mind cooking this thing once I get it re tanked so that's no issue.

I didn't take pictures while taking out and unbolting everything so that was pretty stupid on my part. I had trouble finding any schematics of it online so I did some metering instead to find the resistance in order to distinguish the coils. I got some weird results and I've made a schematic that has my best guess as to what's going on. But first, let me show you the transformer itself:
IMG_5032.jpeg
Top view with HV diodes
IMG_5034.jpeg
Closer view of the rectifier
Here is some labelled diagrams:
IMG_5031.jpeg
Clear view of the two primary inputs and HV diodes
IMG_5033.jpeg
Two secondaries
PA and PB are the primary coils connections. SA and SB are the secondary outputs. The resistance seems to be pretty low for the secondaries and the primaries, but I must have checked eight times to make sure I was getting the right results. Here are the measured resistance between the wires:
Screen Shot 2020-06-09 at 2.20.34 AM.png
Resistance
Screen Shot 2020-06-09 at 2.20.34 AM.png (25.49 KiB) Viewed 772 times
I couldn't find any xray transformer like this one anywhere on the internet or these forums so there was no reference schematics that might have been similar. It seems to be a weird model so I made my own schematics instead. Here is what I think is going on:
IMG_5038.jpeg
Xray transformer
It's a pretty crude photo but this is my best assumption of how it works. I don't think this transformer has a centre tap and instead just has two primary and secondary coils that are fixed on the same iron core. My plan is to connect the two primaries in parallel or series and ground the secondaries SA2 and SB1 to the core. Then I will use the diodes to build a rectifier and ground the positive end to make a negative polarity output. This is what my schematic looks like:
IMG_5039.jpeg
Modified xray transformer
I don't think connecting both primaries is a very good idea so I'm thinking of just using one primary and using the other two secondaries instead. This should work since the fields of one primary should be flow through both secondaries. I'm not sure about grounding the secondary outputs to the transformer core though so I'll need some second opinion on that. Here is what my final design looks like:
IMG_5040.jpeg
This whole design is assuming that my schematic of the transformer in the first place is correct. Can someone confirm that what I came up with is right? I'm going to put some very small voltage across the primaries tomorrow to figure out the ratios but until then I'm assuming everything I have said is correct.

There are obviously pretty hideous mistakes in my logic (that i haven't noticed) but that's why I'm coming to this forum before I go and attempt wiring these things up. I know it seems childish to ask you guys if what I'm doing is wrong but I'm not taking my chanced with this death machine. Thank you for the help!

- AA

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Richard Hull
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Re: Xray transformer mods

Post by Richard Hull » Tue Jun 09, 2020 6:16 pm

You are probably OK and correct. I am not there to verify. I would variac the primary as is and get a ratio in to output to verify. you will need at least a negative 0-10kv DC meter to check.

barely crack the variac off zero and watch to see if

1. the output is negative
2. Bring the output up to almost 10kv.
3. Read and record the AC voltage on the primary.
4. Figure what the ultimate voltage could be.

Re-tank this transformer in the original tank with the oil and let it sit for a few months. No need to heat or vacuum. You should be OK up to about 50kv

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

John Futter
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Re: Xray transformer mods

Post by John Futter » Tue Jun 09, 2020 7:07 pm

usually one winding is for the filament in the x-ray tube.
one of your low resistance windings could be for that
as Riochard has said only crack the variac up a volt or two max

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Richard Hull
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Re: Xray transformer mods

Post by Richard Hull » Wed Jun 10, 2020 4:21 am

John brought up a good point on the filament winding. By variacing the device with a close eye on the AC current in the primary you would see a fast rise on current it you try to power up the filament winding, assuming there is one. It could be that there is no filament in the x-ray tube for this device relying on a field emitter cathode hooked to the negative hv and grounded anode. Fairly common.

Are you sure there is no high ohm contact to the core from any of the HV windings? The cores are joined at their bases to the core normally. Otherwise, there would be a huge mid-point voltage real close to the core. If not, then I am very perplexed.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Ameen Aydan
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Re: Xray transformer mods

Post by Ameen Aydan » Fri Jun 12, 2020 10:35 pm

Sorry for the late response,

Maybe I didn't explain how this transformer works very well. It's rather weird because it has two primaries, two secondaries and two full bridge rectifiers all with the same core. Both primaries and secondaries have the same amount of turns. It also has two filament coils as well, both of which are not mounted on the transformer itself. Here's a photo of the filament transformers:
IMG_5137.jpeg
IMG_5140.jpeg
There seemed to be no high ohm contact to the core from any of the HV windings. I'm not sure why but considering that this still has intact HV silicon diodes, I assume that it's a relatively newer model which accounts for all the weirdness in the design. I don't have much experience in the world of X-ray machines so if anyone has something to say about this transformer please do!

I tested the diodes on it and managed to find the polarity of the DC outputs. Here are some photos:
IMG_5145.jpeg
IMG_5147.jpeg
The diodes are connected to each other as such:
6be7bc6b-0742-4e58-a980-9a59e093d006.jpeg
I also did some measuring and found the turn ratio between the primary and secondary. I didn't want to bring it to 10kv in open air since I was afraid that it may cause some arcing withing the transformer. It's been outside for nearly a year just collecting moisture so I chose against it. Here are the values I got for the voltage and the simple formula for transformers:
PNG image.png
It's pretty messy. If your having trouble understanding please say so!
Due to inefficiencies, there is some voltage loss but as a general note we can assume that there is a 1:180 ratio between the primary and the secondary. That means at 120 volts mains, I can get about 21600 volts from each secondary and for 30 ma on the secondary, that's about 5.5 amps on the primary. I eventually want to see if I can find a transformer that will double the voltage so I can pump 40 kv from each secondary. Until then I'm not sure how I'm gonna get 30kv DC from this transformer. (edit: I found some transformers on eBay so I'll see if I can use those)

Because there is no high ohm contact to the core from any of the HV windings, I'm gonna be moving forward with my idea of grounding two of the secondary AC outputs to make one centre tapped secondary and rectifying the other two outputs, then grounding the + DC. As mentioned, I'll only be using one of the primaries for simplicity sake. I won't be grounding the core since I see no use because there's no contact with any of the windings. The problem here is that I can't get 30kv out of this setup until I get a transformer that will convert 120v to 240v

Another idea I had in mind is keeping the current design of the transformer and connecting the 4 DC outputs. This means taking both -DC outputs and connecting them to each other and grounding the other two +DC outputs. I'm not sure that will work though so this is just an idea to make things more simple and I'm thinking of moving forward with the mods mentioned above. This doesn't solve the problem of getting 30kv since I'm still getting only 21600v out of each secondary

What do you guys think?

I have a bit of school work for the next week, so until then I won't be able to do anything with the PSU other than talk about how to properly modify this thing, sorry.

Thanks for the help!
AA

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Richard Hull
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Re: Xray transformer mods

Post by Richard Hull » Sat Jun 13, 2020 7:50 am

These sound like totally independent isolated supplies. I would go with and work only one supply side and leave the other out of the picture completely! See what voltage and current you can get out of this system. Ground the positive output and run a fusor that is fully metered so you can see what the load is and does to the output voltage and current.

Keep the other supply side as an unconnected spare.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Dennis P Brown
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Re: Xray transformer mods

Post by Dennis P Brown » Sat Jun 13, 2020 5:22 pm

First, great catch getting those two(!) xformers. Also, good work getting their values.

Why add another xformer and get more inefficiencies? Why not just use your 220 volts AC that most all house have?

Since it is under oil, that might be safe but others here would know if that is a good idea. Might be a disaster ... .

Ameen Aydan
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Re: Xray transformer mods

Post by Ameen Aydan » Sat Jun 13, 2020 7:10 pm

Hi,

I would use the 220AC plugs in my house but I don't have a proper variac so I'm limited to 120AC until I get a step up transformer. I wanted to use only one side initially but because the turn ratio for one side is 1:180, I can only get about 40kv from one side (assuming I'm are using 220AC). That 40kv is measuring the potential between the pos and neg output, but since the positive output will be grounded, I would be lucky if I only got half that voltage on the negative side.

http://engineering.electrical-equipment ... ransformer

The url provided explains perfectly what I'm trying to do. By connecting the two secondaries in series, I can double the voltage. I could also rectify both secondaries first, then connect the DC outputs in series and grounding the +DC outputs. Both ideas should work, at least I think...

At the moment, I don't even have a vacuum chamber assembled (but I have all the parts) so I can only measure the voltage unloaded. Until then what should I do to properly test my supply?

EDIT: I just wanted to add a question. I've heard that connecting two independent power supplies in parallel is usually a bad idea but I couldn't find anything saying that a series connection is a bad idea. Is there any reason as to why I shouldn't?

Thank you so much for the help!
AA

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