X-ray transmormer issues

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Schnackj
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Joined: Sun Sep 15, 2019 8:29 pm
Real name: Jason

X-ray transmormer issues

Post by Schnackj »

Hello all,

I've been wanting to join the fusor club for a while and have been keeping my eye out for parts as they show up.
I recently acquired a 125 kv 300 ma X-ray transformer with high voltage cables and the control cabinet but am having issues with my initial testing on it and could use some advice from some people with more experience with these power supplies. I know there are a few different styles of transformer with this spec but this one is a ~10 gallon drum with a bolt ring clamp that weighs around 130lbs empty,
When I got the transformer it had been drained of oil, I refilled it with mineral oil and pulled a light vacuum on it and bounced it around a bit and planned to avoid higher voltages for a while. I've been using the auto-transformer that came with the X-ray controller to control the voltage. I also have the center taps tied together with the ammeter between the two. Power is coming in on a 240 volt 30amp circuit with 10ga wire, with the input power set to 80 volts from the auto-transformer (the lowest setting for the x-ray setup) The current draw is very high, the lights dim, the transformer makes a lot of noise, and the ammeter between the two secondary coils pegs at 300ma. Using my multi meter it looks like its only a bit above the 300ma, this is with no cables plugged into the secondary plugs so it should be an open circuit. This made me think there must be an issue on the secondary coil. I found some taps on the auto transformer to get ~8 volts and figured I could do some lower voltage testing on the anode and cathode outputs to get a better understanding of whats going on, I attached a schematic of the transformer as well.
The transformer is supposed to take 240V in and output 125kv DC between the anode to the cathode ~1:520, the center taps are connected to ground and should be 62.5kvdc between either the anode or cathode to ground
When the transformer is connected to the 8v tap of the auto transformer I measure 7.87v across the primary, 25ma between the center taps G and M1 on the schematic, 39 vdc between the anode to cathode, 57vdc between the anode to ground, and 20vdc between the cathode to ground.
shouldn't I expect 4kv between the anode and cathode and 2kv between each to ground and see 0ma....
I'm at a bit of a loss and hope someone with more experience with these transformers can give me a tip. should I be looking at the rectifiers or rewinding secondary coils, what other safe testing can I do to trace the problem?
Attachments
a700 transformer.PNG
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Richard Hull
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Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: X-ray transmormer issues

Post by Richard Hull »

Get an AC ammeter hook it in series between the variac and the primary. Very slowly, turn up the variac and observe the current. I should be and remain under 1 amp as you raise the primary voltage. If it climbs rapidly turn off the variac. You may have bad diodes.

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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