X-ray Transformer Question

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Patrick Houlihan
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X-ray Transformer Question

Post by Patrick Houlihan »

Hi, just looking for a sanity check on what I’m going to be working on later tonight, the attached images arnt mine but they are the same transformer exactly, so my conundrum is, weather I should wire the 2 coils in series without a center tap, in cerise with a center tap, or in parallel
I remember when I was messing with obits that when you use a center tap and 2 diodes to rectify you only get half the current throughput or something so I didn’t know if it would make more sense to just paralell the coils or if wiring it with center tap was the optimal condition

As always any help or insight is greatly appreciated
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Richard Hull
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Re: X-ray Transformer Question

Post by Richard Hull »

If your polarity dots are correct, F to G is correct leaving a center tap or core as ground. Two very high voltage diodes are all that is needed to get full wave rectification. Do not parallel connect the windings.
Just be careful and put the entire supply under oil when done.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Rich Feldman
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Re: X-ray Transformer Question

Post by Rich Feldman »

Yes, what Richard said. There's more to be seen.

From the paper diagram, we see that upper HV winding has non-dot end grounded. That's the "start" of winding, on inside layer, not insulated (even under oil) for the nominal kV value.
Based on normal x-ray generator use, lower HV has dot on the start end (F), which is also not insulated for HV. In normal service, F is connected to G (ground) through a current-measuring shunt. If that shunt were to go open circuit, very high voltage would appear across the gap.

In your two-diode full wave rectified configuration, half of the DC current is present in F-G link, and half is in the grounding connection of upper winding. If that connection is accessible, you could configure the circuit to have total-current monitor between HV secondary center tap and ground.

Each diode must withstand double the full-wave-rectified output voltage. For example, if you crank up the transformer to get -25 kV at common anode, when one cathode is at -25 kV the other cathode is at +25 kV.
All models are wrong; some models are useful. -- George Box
Kyler Johnson
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Re: X-ray Transformer Question

Post by Kyler Johnson »

I'm using the same transformer that this post is referencing and I'm unsure of how to wire F to G.
Screen Shot 2024-01-02 at 10.49.06 PM.png
Screen Shot 2024-01-02 at 10.49.24 PM.png
Based on these pictures, how should I wire F to G? Do I need to wire F directly to the center tap inside the transformer? Or can I simply wire F to the metal shown in the first picture?
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Richard Hull
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Re: X-ray Transformer Question

Post by Richard Hull »

If you have the same transformer, tell me, why don't you consult the diagram above??

It is your guide. The work is already done for you. verify with an ohmmeter all the leads as noted above.

I do worry that one of the leads, E or F to the isolated (as drawn) hv winding should go to ground or to the center tap. Check this out.

I am not there and can't make the measurements personally.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Kyler Johnson
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Re: X-ray Transformer Question

Post by Kyler Johnson »

Sorry, I may not have been clear enough. I was moreso asking what the safest way to connect the isolated winding to ground or the center tap is. I have already verified all of the connections on the transformer with a multimeter.
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Richard Hull
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Re: X-ray Transformer Question

Post by Richard Hull »

Much more clear. You will need to observe the polarities of the grounded winding and the isolated winding such that you ground the leg of the isolated winding so that the windings are additive across the total extreme ends of the hot windings. You might need something a bit more than a DVM to verify this additive voltage even with only 2 vac on the primary.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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