Upon arrival the xfer seems to be in tact with no visible damage on the outside. The wires are well-maintained and the data from testing between 8 points is below.
Taylor
X-ray transformer - zero output
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Taylor Romain
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X-ray transformer - zero output
I'm currently testing a General Electric 100kV Xray transformer I received off eBay from 'isoneutron' who has a history of selling Xray transformers suitable for Tesla coils, fusors, and x-ray tubes.
Upon arrival the xfer seems to be in tact with no visible damage on the outside. The wires are well-maintained and the data from testing between 8 points is below. I used a variable auto transformer that outputs 120V max, 60 Hz with a 12 amp fuse to inject 0.5VAC into the xfer with no output being detectable when probed at the secondary and center tap.
The probe is connected to the center tap, and B point. Is there any reason to believe this xfer has a short internally and is non-functioning or I missing something in the test plan?
Taylor
Upon arrival the xfer seems to be in tact with no visible damage on the outside. The wires are well-maintained and the data from testing between 8 points is below. I used a variable auto transformer that outputs 120V max, 60 Hz with a 12 amp fuse to inject 0.5VAC into the xfer with no output being detectable when probed at the secondary and center tap.
The probe is connected to the center tap, and B point. Is there any reason to believe this xfer has a short internally and is non-functioning or I missing something in the test plan?
Taylor
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Taylor Romain
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Re: X-ray transformer - zero output
To add, there is 66kOhms between D and the copper contact.
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Rich Feldman
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Re: X-ray transformer - zero output
Hi Taylor. Sounds like you've made a good start.
Would expect that 0.5 volts on primary is enough to get measurable core magnetization, even with nonlinearity & hysteresis. Magnetic flux should be on the same order as applying 120 or 240 volts to one of the half-secondary windings while measuring voltage on primary and the other half secondary.
[edit] I see you did post a matrix of DC resistance measurements. It's puzzling because we see 72k between H and the B,F pin pair, with only 1.5 ohms between B and F. Would expect to see double resistance between the outside end of two secondary windings. The transformer seller, if reputable, ought to have the knowledge and willingness to help you.
More than 10 years ago I reported some charactaristics of a dental XRT:
viewtopic.php?t=4805
Some follow-up thread included measurements on the bench with voltage up to 1000 VAC on half-secondaries. And explanation of some resistor on the order of 100 kilohms, built into transformer, on the cathode end -- it's for current-dependent bias voltage on "grid" or "focus" terminal of the Coolidge tube. I have never followed through to get that XRT potted and operated at full voltage.
Would expect that 0.5 volts on primary is enough to get measurable core magnetization, even with nonlinearity & hysteresis. Magnetic flux should be on the same order as applying 120 or 240 volts to one of the half-secondary windings while measuring voltage on primary and the other half secondary.
[edit] I see you did post a matrix of DC resistance measurements. It's puzzling because we see 72k between H and the B,F pin pair, with only 1.5 ohms between B and F. Would expect to see double resistance between the outside end of two secondary windings. The transformer seller, if reputable, ought to have the knowledge and willingness to help you.
More than 10 years ago I reported some charactaristics of a dental XRT:
viewtopic.php?t=4805
Some follow-up thread included measurements on the bench with voltage up to 1000 VAC on half-secondaries. And explanation of some resistor on the order of 100 kilohms, built into transformer, on the cathode end -- it's for current-dependent bias voltage on "grid" or "focus" terminal of the Coolidge tube. I have never followed through to get that XRT potted and operated at full voltage.
All models are wrong; some models are useful. -- George Box
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Taylor Romain
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Re: X-ray transformer - zero output
Here I present some analysis from testing a high voltage xray transformer. After some more familiarity with the xray transformer and tossing out a bad alligator lead, I was able to get output from one of the high voltage secondaries and begin planning construction for the high voltage power supply. Also it is noted the the scope was set to DC coupling at the time measurements were taken. Oversight.
Between point F and center tap there is 72.0k ohms, this is one of the high voltage secondaries.
Between the copper pad and a copper strand between the two AC inputs there is 65k ohms, this is the other secondary. It is noted the that this secondary is an open circuit when measured with respect to center-tap. Points F and B were shorted with 1.5 ohms measured between them. The same is true for Points G and A.
For testing I began by injecting 0.5 VAC through a variac into the primary. 0.5V is used for all test cases. I used a Digital Siglent SDS 1104X-E oscilloscope and Klein MM400 multimeter for voltage measurement.
Measured between point F and center-tap
MM400 measured voltage is equal to 163.8.
SDS 1104X-E measured voltage is equal to 167.89.
Measured between the copper pad and center-tap
MM400 measured voltage is equal to 27.5.
SDS 1104X-E measured voltage is equal to 44.83.
[1] Measured between point F and center-tap / [2] Measured between the copper pad and center-tap indicated a 90 degrees phase shift.
When the copper strand was connected to the center tap and the copper pad was re-measured, the phase shift relative to the other secondary measurement was 180 degrees, allowing the secondary to produce an effective voltage equal to that of the other secondary.
Measured between point F and center-tap with the copper strand referenced to center-tap
MM400 measured voltage is equal to 166.2V.
SDS 1104X-E measured voltage is equal to 170.22V
Measured between the copper pad (D) with the copper strand referenced to center-tap. I do not have a static connection to the pad so I held the oscilloscope probe to the pad.
MM400 measured voltage is equal to 165.0.
SDS 1104X-E measured voltage is equal to 169.0
With all that in mind, will the 180 degrees phase shift between the two secondaries cancel each other out when rectified to negative DC using diodes?
Between point F and center tap there is 72.0k ohms, this is one of the high voltage secondaries.
Between the copper pad and a copper strand between the two AC inputs there is 65k ohms, this is the other secondary. It is noted the that this secondary is an open circuit when measured with respect to center-tap. Points F and B were shorted with 1.5 ohms measured between them. The same is true for Points G and A.
For testing I began by injecting 0.5 VAC through a variac into the primary. 0.5V is used for all test cases. I used a Digital Siglent SDS 1104X-E oscilloscope and Klein MM400 multimeter for voltage measurement.
Measured between point F and center-tap
MM400 measured voltage is equal to 163.8.
SDS 1104X-E measured voltage is equal to 167.89.
- Measured between point F and center-tap.
Measured between the copper pad and center-tap
MM400 measured voltage is equal to 27.5.
SDS 1104X-E measured voltage is equal to 44.83.
- Measured between the copper pad and center-tap.
[1] Measured between point F and center-tap / [2] Measured between the copper pad and center-tap indicated a 90 degrees phase shift.
- [1] Measured between point F and center-tap / [2] Measured between the copper pad and center-tap indicated a 90 degrees phase shift.
When the copper strand was connected to the center tap and the copper pad was re-measured, the phase shift relative to the other secondary measurement was 180 degrees, allowing the secondary to produce an effective voltage equal to that of the other secondary.
Measured between point F and center-tap with the copper strand referenced to center-tap
MM400 measured voltage is equal to 166.2V.
SDS 1104X-E measured voltage is equal to 170.22V
- Measured between point F and center-tap with the copper strand referenced to center-tap.
Measured between the copper pad (D) with the copper strand referenced to center-tap. I do not have a static connection to the pad so I held the oscilloscope probe to the pad.
MM400 measured voltage is equal to 165.0.
SDS 1104X-E measured voltage is equal to 169.0
- Measured between the copper pad (D) with the copper strand referenced to center-tap.
- [1] Measured between point F and center-tap / [2] Measured between the copper pad and center-tap indicated a 180 degrees phase shift after referencing the copper strand to center-tap.
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Rich Feldman
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Re: X-ray transformer - zero output
Good work!
>> With all that in mind, will the 180 degrees phase shift between the two secondaries cancel each other out when rectified to negative DC using diodes?
Don't know what you mean by cancel, but it's good. Assuming full-wave rectification with two diodes, and return path through a current measuring shunt to the common center tap.
Rectified output gets two half-sine pulses every cycle of AC input.
Mind your diode voltage ratings.
When one secondary is at, say, -25 kV, that pulls the rectified output to -25 kV.
At that instant, the other secondary is at +25 kV, so its rectifier diode is subject to 50 kV of reverse bias.
>> With all that in mind, will the 180 degrees phase shift between the two secondaries cancel each other out when rectified to negative DC using diodes?
Don't know what you mean by cancel, but it's good. Assuming full-wave rectification with two diodes, and return path through a current measuring shunt to the common center tap.
Rectified output gets two half-sine pulses every cycle of AC input.
Mind your diode voltage ratings.
When one secondary is at, say, -25 kV, that pulls the rectified output to -25 kV.
At that instant, the other secondary is at +25 kV, so its rectifier diode is subject to 50 kV of reverse bias.
All models are wrong; some models are useful. -- George Box
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Rich Gorski
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Re: X-ray transformer - zero output
Taylor,
Did Isoneutron provide you with a schematic of the transformer? If so please post.
X-ray tube transformers can be quite complex as the common rotating anode X-ray tube requires filament current, beam focus adjustment as well as the high voltage to produce X-rays all provided by the transformer. Since there are two secondaries I assume one is for the tube anode high voltage and the other for beam focus control. The center taps could be used to measure electron beam current with an milli-ammeter. The ammeter essentially shorts the center tap to ground. Complicated if you don't have the schematic to know you which lead is which.
Rich G.
Did Isoneutron provide you with a schematic of the transformer? If so please post.
X-ray tube transformers can be quite complex as the common rotating anode X-ray tube requires filament current, beam focus adjustment as well as the high voltage to produce X-rays all provided by the transformer. Since there are two secondaries I assume one is for the tube anode high voltage and the other for beam focus control. The center taps could be used to measure electron beam current with an milli-ammeter. The ammeter essentially shorts the center tap to ground. Complicated if you don't have the schematic to know you which lead is which.
Rich G.
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Taylor Romain
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Re: X-ray transformer - zero output
Rich G,
I do not have a schematic, it has been hard to find. From past research I believe the transformer is a General Electric 100 kV - 120 kV Xray transformer. Past posts such as viewtopic.php?t=12646 also indicate that it may be rated up to 120 kV. I believe Andrew Seltzman design also uses the same transformer per http://www.rtftechnologies.org/physics/ ... former.htm.
I do not have a schematic, it has been hard to find. From past research I believe the transformer is a General Electric 100 kV - 120 kV Xray transformer. Past posts such as viewtopic.php?t=12646 also indicate that it may be rated up to 120 kV. I believe Andrew Seltzman design also uses the same transformer per http://www.rtftechnologies.org/physics/ ... former.htm.
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Taylor Romain
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Re: X-ray transformer - zero output
I believe the schematic would look like this
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Rich Gorski
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Re: X-ray transformer - zero output
Taylor,
Thanks for the schematic, I have to say I'm confused. I think you need to redo the table of resistances that you presented in your first post to confirm your schematic. Identify all the leads with alphabetic labels including the copper pad, the copper strand, ground, core etc. Also please indicate the difference between a direct short and a low resistance reading and also infinite readings. Please also use larger type as it was hard to read the table on my computer screen. If you have definitely identified the AC input (primary) please indicate which those are. If there is a ground connection (core ?) please include readings with respect to that.
It would also be great if you could do a second table with RMS voltage readings from your multimeter with 0.5VAC on the primary.
Thanks,
Rich G.
Thanks for the schematic, I have to say I'm confused. I think you need to redo the table of resistances that you presented in your first post to confirm your schematic. Identify all the leads with alphabetic labels including the copper pad, the copper strand, ground, core etc. Also please indicate the difference between a direct short and a low resistance reading and also infinite readings. Please also use larger type as it was hard to read the table on my computer screen. If you have definitely identified the AC input (primary) please indicate which those are. If there is a ground connection (core ?) please include readings with respect to that.
It would also be great if you could do a second table with RMS voltage readings from your multimeter with 0.5VAC on the primary.
Thanks,
Rich G.
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Rich Feldman
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Re: X-ray transformer - zero output
A common feature in dental x-ray generators is to develop bias voltage for the focus cup (aka "grid") using a fixed resistor between focus terminal and one end of filament. Develops a negative bias voltage, on the order of couple hundred volts, proportional to current in the HV loop.
Long ago I reported on a transformer unit with three terminals on the HV coil module for cathode. IIRC, the filament winding and the bias resistor were both inside it. For application where the Coolidge tube was self-rectifying, so the other HV coil module had direct connection from half-secondary winding to the anode.
[edit] there it is! viewtopic.php?t=4805
[edit edit] and more to the point viewtopic.php?p=73983#p73983
Long ago I reported on a transformer unit with three terminals on the HV coil module for cathode. IIRC, the filament winding and the bias resistor were both inside it. For application where the Coolidge tube was self-rectifying, so the other HV coil module had direct connection from half-secondary winding to the anode.
[edit] there it is! viewtopic.php?t=4805
[edit edit] and more to the point viewtopic.php?p=73983#p73983
All models are wrong; some models are useful. -- George Box
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Taylor Romain
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Re: X-ray transformer - zero output
Rich G,
Sorry for the confusion. I've updated the resistance mapping, some of the test points were missing from the original mapping posted.
edit: I have added the voltage measurements taken from each secondary with point Z not connected to center-tap (H) and with it connected to center-tap (H). 0.517VAC was injected into the primary through points C&E. A MM400 multimeter was used to take AC measurements. Apologies for the small image in the post. If you click on it, it will expand and be easy to read.
Sorry for the confusion. I've updated the resistance mapping, some of the test points were missing from the original mapping posted.
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Rich Gorski
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Re: X-ray transformer - zero output
Taylor,
With 0.5VAC applied to inputs E & C, can you measure output voltage between points F & D with H grounded and not grounded. I think you will see about 330V between F & D.
Thanks,
Rich G.
With 0.5VAC applied to inputs E & C, can you measure output voltage between points F & D with H grounded and not grounded. I think you will see about 330V between F & D.
Thanks,
Rich G.
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Rich Gorski
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Re: X-ray transformer - zero output
Another measurement:
Looking again at your resistance measurements I see that point A and point G show a short so they appear to be connected together as do B & F. However point G shows infinite resistance to every other point as if A&G are not connected to any other windings yet there is 88 volts appearing between point G and H. So, could you take a look again at point G and see if you measure resistance to any other point?
Also, are any of the points obviously connected to ground... the core of the transformer?
Thanks again,
Rich
Looking again at your resistance measurements I see that point A and point G show a short so they appear to be connected together as do B & F. However point G shows infinite resistance to every other point as if A&G are not connected to any other windings yet there is 88 volts appearing between point G and H. So, could you take a look again at point G and see if you measure resistance to any other point?
Also, are any of the points obviously connected to ground... the core of the transformer?
Thanks again,
Rich
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Taylor Romain
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Re: X-ray transformer - zero output
The center tap is grounded to the core. The only point connected that has measured resistance between center-tap are points F/B which are shorted together.
I've re-checked point G and it is not connected to anything else nor shows any resistance measurements besides G&A which are shorted.
With 0.5V injected into the primary when point H is earth grounded the AC measurement taken by multimeter between points F&D is 83.5V. With H not earth grounded the AC measurement taken by multimeter between points F&D is 74.6V. Point Z is not connected to H.
With 0.7V injected into the primary when point Z is connected to center-tap (H) the AC measurement taken between points F&D is 350.3 V. Point F measured to H is 224.3 V. Point F measured to H is 224.6 V. Points F and D are 180 degrees out of phase with each other referenced to center-tap when Z is connected to C-T.
I've re-checked point G and it is not connected to anything else nor shows any resistance measurements besides G&A which are shorted.
With 0.5V injected into the primary when point H is earth grounded the AC measurement taken by multimeter between points F&D is 83.5V. With H not earth grounded the AC measurement taken by multimeter between points F&D is 74.6V. Point Z is not connected to H.
With 0.7V injected into the primary when point Z is connected to center-tap (H) the AC measurement taken between points F&D is 350.3 V. Point F measured to H is 224.3 V. Point F measured to H is 224.6 V. Points F and D are 180 degrees out of phase with each other referenced to center-tap when Z is connected to C-T.
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Rich Gorski
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Re: X-ray transformer - zero output
Taylor,
One last (I hope) question... in that last measurement where you measured 350.3V between F/B and D and with Z connected to H, was Z/H also earth grounded? If not can you earth ground Z/H and measure F/B to D? I think you will still see 350.3 volts.
Rich G.
One last (I hope) question... in that last measurement where you measured 350.3V between F/B and D and with Z connected to H, was Z/H also earth grounded? If not can you earth ground Z/H and measure F/B to D? I think you will still see 350.3 volts.
Rich G.
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Taylor Romain
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Re: X-ray transformer - zero output
Yes point H was earth grounded with Z connected as well.
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Rich Gorski
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Re: X-ray transformer - zero output
Taylor,
Ok, I think you’ve identified enough of this transformer to go ahead and turn it into a fusor power supply. With the center tap (H) grounded and connected to Z, the secondary to connect to the fusor are points F/B and D. Here’s a schematic of what I think the transformer looks like. I've also included a fusor circuit to get you started. .... If anyone else has additional information please chime in ...
Based on your measurements with 0.7 VAC input on C&E the output across F/B & D is 350 VAC. That is 500 VAC per volt so putting in 120VAC should generate 60,000 Volts between F/B and D. However if you use the circuit as I have drawn you will get half the voltage between the CT and each side of the secondary or 250V per volt ratio for the fusor. So, using the circuit above and with 120VAC input you should see 30,000 VAC output. This will give you 30,000 * 1.414 = 42400 peak output applied to the fusor grid. A very respectable fusor voltage and you might go higher if you can increase the input voltage with a Variac.
You could try to ground either F/B or D (with H left open) and I think you will see the full 500 per volt on the other side but I believe this transformer is designed to run an X-ray tube with the center tap grounded and about half the voltage is developed between the center tap and each side of the secondary. On an X-ray tube the negative side would be connected to the filament and the positive side connected to the anode. So the X-ray tube sees the full voltage to accelerate electrons but the transformer insulation only see a max of half the voltage. Easier for insulation and high voltage cables. If you try grounding one side of the secondary and leave H open to get full voltage you might exceed the insulation capability of the transformer.
A few things to remember:
1) This is a dangerous transformer. Give it lots of respect.
2) The transformer has to be immersed in mineral oil. Pull a vacuum on the tank to get all the air pockets out.
3) The diode string need to be capable of handling more than the peak voltage of what the transformer will output. A string of smaller voltage diodes in series is one way to handle this.
I think the next thing I would do is connect a high wattage resistor between F/B and D to check what current it can deliver (no diodes). With 1.0 VAC input you should get 500 volts between F/B & D. So a 25k OHM resistor would draw 20 mA and dissipate 10 Watts of power. You can measure the voltage across the resistor with your DVM. You probably will have to go higher than 1.0VAC to get 500VAC output when its loaded down with the 25K resistor.
Keep posting on your progress.
Rich G.
Ok, I think you’ve identified enough of this transformer to go ahead and turn it into a fusor power supply. With the center tap (H) grounded and connected to Z, the secondary to connect to the fusor are points F/B and D. Here’s a schematic of what I think the transformer looks like. I've also included a fusor circuit to get you started. .... If anyone else has additional information please chime in ...
Based on your measurements with 0.7 VAC input on C&E the output across F/B & D is 350 VAC. That is 500 VAC per volt so putting in 120VAC should generate 60,000 Volts between F/B and D. However if you use the circuit as I have drawn you will get half the voltage between the CT and each side of the secondary or 250V per volt ratio for the fusor. So, using the circuit above and with 120VAC input you should see 30,000 VAC output. This will give you 30,000 * 1.414 = 42400 peak output applied to the fusor grid. A very respectable fusor voltage and you might go higher if you can increase the input voltage with a Variac.
You could try to ground either F/B or D (with H left open) and I think you will see the full 500 per volt on the other side but I believe this transformer is designed to run an X-ray tube with the center tap grounded and about half the voltage is developed between the center tap and each side of the secondary. On an X-ray tube the negative side would be connected to the filament and the positive side connected to the anode. So the X-ray tube sees the full voltage to accelerate electrons but the transformer insulation only see a max of half the voltage. Easier for insulation and high voltage cables. If you try grounding one side of the secondary and leave H open to get full voltage you might exceed the insulation capability of the transformer.
A few things to remember:
1) This is a dangerous transformer. Give it lots of respect.
2) The transformer has to be immersed in mineral oil. Pull a vacuum on the tank to get all the air pockets out.
3) The diode string need to be capable of handling more than the peak voltage of what the transformer will output. A string of smaller voltage diodes in series is one way to handle this.
I think the next thing I would do is connect a high wattage resistor between F/B and D to check what current it can deliver (no diodes). With 1.0 VAC input you should get 500 volts between F/B & D. So a 25k OHM resistor would draw 20 mA and dissipate 10 Watts of power. You can measure the voltage across the resistor with your DVM. You probably will have to go higher than 1.0VAC to get 500VAC output when its loaded down with the 25K resistor.
Keep posting on your progress.
Rich G.
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Taylor Romain
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Re: X-ray transformer - zero output
Thank you for assisting me so far in analyzing this transformer, it indeed is very dangerous to work with.
For now, I've gathered the following components for the circuit. I've referenced R. Hulls '#4b FAQ - Wiring for real fusion fusor - part two' for the necessary electrical components'.
2 x 10kV 100M ohm 5W, 5% glass-glaze film resistors
12 x 20kV, 20mA high voltage rectifier diodes
-5 diodes arranged in a series string for each secondary
1 x 10 ohm 5W, 5% cement resistor
1 x 60k ohm 100W wire wound resistor
1 x gallon of technical grade light mineral oil
1 x 11.75 x 10.23 x 7.46 in container
The next step for the HV power supply is to layout where everything is going to go within the container. Now that I have some of the circuit components, spacing may become an issue within the container.
When it comes to submerging the xfer and electrical connections in mineral oil, this xfer did not come with a pre-built container. The best option beyond applying a vacuum is to heat the oil to 50C as well as the xfer according to Mr. Dennis P Brown:
For now, I've gathered the following components for the circuit. I've referenced R. Hulls '#4b FAQ - Wiring for real fusion fusor - part two' for the necessary electrical components'.
2 x 10kV 100M ohm 5W, 5% glass-glaze film resistors
12 x 20kV, 20mA high voltage rectifier diodes
-5 diodes arranged in a series string for each secondary
1 x 10 ohm 5W, 5% cement resistor
1 x 60k ohm 100W wire wound resistor
1 x gallon of technical grade light mineral oil
1 x 11.75 x 10.23 x 7.46 in container
- 60k ohm 100W ballast wire wound resistor
- 10 ohm 5W, 5% cement resistor
- 100M ohm, 10kV, 5W, 5% glass-glaze film resistor
- Crystal Plus Tech Grade Mineral Oil 70T - 1 gal
- 11.75 x 10.23 x 7.46 in) Clear/Clear UL 508A Polycarbonate IP67 Waterproof Plastic Cabinet
When it comes to submerging the xfer and electrical connections in mineral oil, this xfer did not come with a pre-built container. The best option beyond applying a vacuum is to heat the oil to 50C as well as the xfer according to Mr. Dennis P Brown:
Would this be an ideal approach? Heat the oil say in a glass beaker/flask on a hot plate and then gradually add it into the container?Dennis P Brown wrote: ↑Sat Feb 16, 2019 9:54 am Since surface tension and air being trapped deep in the coil are the main issues, simply "bumping" the item while it is under oil is not likely to remove these types of issues. Certainly it will help for bubbles on the x-former surface.
I would suggest, in lieu of vacuum, heating the oil and transformer up to 50 C and this would do far more. Besides helping to drive off water within the coil, small bubbles will expand, the viscosity of the oil will get lower, and the copper winding's will also expand all helping to force out air and make it easier for the oil to penetrate.
Others may weigh in with better advice but this is extremely simple to do and offers a better chance of success compared to just "bumping" or soaking alone.
viewtopic.php?t=12646
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Rich Gorski
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Re: X-ray transformer - zero output
Taylor,
Heating the oil will make it more watery and will help if you can tilt the container and slosh oil around. However you have a much better chance of getting all the air pockets out if you can pull a bit of a vacuum on it. Just a bucket like container with a cover that you can get a reasonable seal (tape ?) and with a port of some kind to connect a vacuum hose. Any kind of cheap vacuum pump should do the job (battery powered, manual ?) as long as you see bubbles forming in the oil. Then you know it's pulling air out. If you leave an air pocket in a high electric field area of the transformer it could arc and create a short.
I have never done this so a don't have direct experience with it but the vacuum approach seems straight forward.
Good luck.
Rich G.
Heating the oil will make it more watery and will help if you can tilt the container and slosh oil around. However you have a much better chance of getting all the air pockets out if you can pull a bit of a vacuum on it. Just a bucket like container with a cover that you can get a reasonable seal (tape ?) and with a port of some kind to connect a vacuum hose. Any kind of cheap vacuum pump should do the job (battery powered, manual ?) as long as you see bubbles forming in the oil. Then you know it's pulling air out. If you leave an air pocket in a high electric field area of the transformer it could arc and create a short.
I have never done this so a don't have direct experience with it but the vacuum approach seems straight forward.
Good luck.
Rich G.
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Dennis P Brown
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- Real name: Dennis Brown
Re: X-ray transformer - zero output
I've done the vacuum pull. I bought a large glass cylindrical shaped storage container (rather thick glass, too) from walmart. I added an aluminum plate cover(with a small pipe glued into a hole I drilled) and cut a simple o-ring rim gasket from some rubber like sheet I got from ebay. The glass container was more than big enough for my transformer. No idea if such is available in the size you need but worth looking for such at the store.
Ignorance is what we all experience until we make an effort to learn
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John Futter
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Re: X-ray transformer - zero output
If you do a vacuum pull you will have to have a pump capable of going below 1^-10^2 millibar as this is the vapour pressure of water---the killer of high voltage insulation in transformers, and you have to pump for many many hours if not days
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Taylor Romain
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Re: X-ray transformer - zero output
Thanks for the insight, I have two mechanical pumps right now for use,
1) Kozyvacu TA5000 Dual Stage rated for 5 microns
2) Edwards E1M18 Single Stage rated for 22 microns
I believe the Edwards pump would be ideal for this process as it can deliver the pressures needed to pull out water molecules as well as run for significant durations of time. The Edwards pump also has a gas ballast to minimize contamination of water within the pumps oil during this process.
1) Kozyvacu TA5000 Dual Stage rated for 5 microns
2) Edwards E1M18 Single Stage rated for 22 microns
I believe the Edwards pump would be ideal for this process as it can deliver the pressures needed to pull out water molecules as well as run for significant durations of time. The Edwards pump also has a gas ballast to minimize contamination of water within the pumps oil during this process.
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Rich Gorski
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- Location: Illinois
Re: X-ray transformer - zero output
Either of those pumps will work fine and may even be an overkill for a gallon of mineral oil. Degassing oil for transformers is generally done at a few 10s of Torr pressure above the liquid. Heating the oil will also increase the efficiency of the degassing process. If you want to really understand the degassing process/theory, look up Henry's law. It states that the amount of gas absorbed in a liquid is directly proportional to the partial pressure above the liquid (I think I got that right). So any pressure below atmosphere will begin the degassing process. You just want it low enough so you don't have to wait a year for all the gas to be liberated.
Rich G.
Rich G.
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Taylor Romain
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- Real name: Taylor Romain
Re: X-ray transformer - zero output
Would you recommend against using a stainless steel container for housing the xray transformer even if the case is earth grounded?
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Dennis P Brown
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- Real name: Dennis Brown
Re: X-ray transformer - zero output
The issue is with a metal container is used to OPERATE the x-former the danger is due to the very fact there is an Earth ground; any wire or x-former section close enough to a grounded metal surface is a potential arc over section. And that could destroy the x-former. Further, a grounding wire may be detached somehow and the case could become lethal. Metal is a bad idea when so many plastic containers are available - IMO.
If you mean pump down, of course.
If you mean pump down, of course.
Ignorance is what we all experience until we make an effort to learn