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BradStockdale

Wed Jun 10 2009, 03:28PM

Registered Member #2119 Joined: Mon May 11 2009, 04:30PM
Location:
Posts: 15

Everyone,

I got around to breaking down the unit that I got out of my x-ray head. The transformers, diodes, and tube were all bolted together into one assembly. Took the tube out the day I opened the head. And last night I took apart the transformers and such... Attached are some images of the high voltage transformer, filament transformer, and diode strings (at least, I think that's what they are!)...

Anyone have any ideas on figuring out how to connect the high voltage transformer? I've got a bucket that I'm going to use as an enclosure... Filled with oil, of course. The HV transformer has seven wires emerging total. Two are obviously the high voltage wires... The other five are the ones that I'm not sure about. Three of them are roughly 16 gauge wire. Two others are probably 18 gauge. Slightly thinner...

How would I go about figuring out how to wire the primary? Measure the resistance between all the wires and try to map it out that way?

Also, the diode strings look a bit odd. They had 'caps' made out of paper covering pairs of the diodes. There's no writing on the little cylinders under the caps. They are all wired in series. They almost look like little rolled capacitors, but they have to be diodes...

Anyway, if anyone has any advice on figuring out the primary wiring, I'd love to hear it!

Thanks!
Brad

...

Wed Jun 10 2009, 05:30PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Did the wiring in the head give you any clues? I would guess that the 2 fatter wires are the primary and the thinner ones are the secondary ground and possibly a filament

Steve Conner

Thu Jun 11 2009, 11:20AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

It can't be 3 phase because then the core would have three limbs and there would be three HV windings. It must be single phase.

You should find that the thick wires are primaries, and the thin ones are the earthy ends of the HV windings. By earthy end I mean that the transformer is probably designed to run with these wires grounded to the core, like a MOT. In X-ray machines they usually connect the tube current meter in series with these wires, and that's why they're brought out of the tank.

Some X-ray transformers run at higher than line frequency and are powered by an inverter in the control box. They do this because it makes the transformer smaller, and allows use of a CW multiplier, so the transformer can be wound for a lower voltage, which makes it smaller and cheaper still, until you get to a point where the saving pays for the inverter.

Proud Mary

Thu Jun 11 2009, 11:28AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Isn't there are a danger that having removed the transformer from the oil, that air may have entered the windings? The smallest air bubble will form a corona at these voltages, so won't you need to pump it down in an oil bath before you can use it?

BradStockdale

Thu Jun 11 2009, 01:55PM

Registered Member #2119 Joined: Mon May 11 2009, 04:30PM
Location:
Posts: 15

Regarding single versus three phase: The whole unit was labeled as being single phase 220VAC 60 Hz. So, I assume that the transformer is also single phase. Besides, there's not enough windings to be three phase...

Regarding being out of oil: I suppose that is a risk... I need to find new oil for it... Not enough of the old stuff (which wasn't pretty anyway) to fill the new housing... I went to Lowes and Home Depot looking for mineral oil, but neither of them sell it anymore... Went to the drugstore and the largest bottle I could get was 12 oz and they wanted $4.00 for that bottle. I'd need a lot of those to fill a 2 gallon plastic housing! There's gotta be a cheaper place to get it than that...

I researched transformer oil options here on the forums and found a lot of different advice... Including using various plant based oils... However, I'd really prefer mineral oil or something synthetic so I do not have to worry about it going rancid on me over time.

Also, I have several vacuum pumps (an old roughing pump that doesn't work real well anymore, and an HVAC oriented vacuum pump... I guess I could put a fitting on the 'housing' to allow me to pump it down some so the oil would penetrate better. That's more work, but I want to heed your warning about there possibly being minute air pockets since its been out of the oil for a week now...

Regarding the two small wires being for the filament: But, there was a separate filament transformer in the assembly. So that can't be what it was for.. .At least, I think it was a filament transformer -- it's the small one in the photos I posted...

Thanks for all the thoughts everyone!! I'll take any advice I can get.

By the way -- I saw that a few members have had success getting transformer oils by approaching the local power companies... I was thinking about trying that too... I don't know if I'll have any success, but it's worth a shot... I guess the worst that can happen is I get some weird looks and a "NO".... I don't have any contacts at the power company, really... WAIT... I know someone who works at one of the local power PLANTS... But I haven't talked to him in a long time. I'd feel bad just appearing out of nowhere after years, only to ask for transformer oil. Hmm.

What about hydraulic oil? I could probably buy that at the local NAPA auto parts store... The have a side business of making hydraulic hoses and fittings... They'd probably have it in 5 gallon jugs, or bigger... Anyone ever used hydraulic oil as transformer oil?

Thanks,
Brad

rp181

Thu Jun 11 2009, 02:44PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

A while ago I came across this:

15$ for 1 quart of oil. They have alot for sale, so you can probably email them and ask if they have more, and if they can give a "bulk" discount.

Proud Mary

Thu Jun 11 2009, 03:56PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Vegetable dielectric oil is increasingly used in industry at very high voltages and high powers, as I have pointed out in many previous threads.

Nowadays there is no good reason for using harmful 'mineral oil' when the whole industry is moving towards the use of of environmentally friendly and less flammable vegetable dielectric oils.

There is a lot of scientific, commercial, and patent literature online about vegetable dielectric oil, its properties, preparation, purification and stabilization, so it's often best to look to sources like these before worrying about 'rancidity' - what are you thinking of, a burger restaurant?

rp181

Thu Jun 11 2009, 04:03PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

Since you don't plan on using the x-ray tube (from what I have gathered), do you plan on just using the transformer for arcs and such?

BradStockdale

Thu Jun 11 2009, 06:58PM

Registered Member #2119 Joined: Mon May 11 2009, 04:30PM
Location:
Posts: 15

Yes, arcs and such.

I used to be deeply interested in nuclear physics... But not so much anymore. I don't have the proper safety equipment to experiment with x-rays now. Maybe someday in the future once I put together a decent scintillation detector and get lead shielding and such. Not in the near future, though.

Arcstarter

Thu Jun 11 2009, 10:09PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

I would also suggest not using it with the full voltage unless you can find a good dielectric oil and pump that thing down!

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