Why Is there 3-Phase?

On 5/10/07 5:43 PM, in article snipped-for-privacy@4ax.com, "The Great Attractor"


There are dc driven x-ray equipments for things like portable hand held devices. I am willing to bet that most of the things you worked obtained power over three-phase lines--even at airports. You just conditioned it to be dc.
As a kid, I remember going to a dentist in the New York City region supplied by dc. The dc was not used to power x-ray tubes directly. A motor generator set was used to convert to ac which could be stepped up AND RECTIFIED to produce dc for the tube.
As far as I know, that may have been the only time I had an x-ray taken without a three-phase power being involved. In retrospect, I now believe that three-phase power was sent into this area to be converted to distributed dc.
Bill -- Fermez le Bush--about two years to go.
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wrote:

Wrong. They were DC POWER SUPPLIES. It had nothing to do with the source power. THEY WERE DC POWER SUPPLIES.
NOTHING to do with any "handheld device" either.
The Los Alamos unit was a 50kV DC supply.
DIRECT CURRENT.
ALL X-ray sources are DC fed. I do not know of any that are not.
The electron beam has to STRIKE the target, not emit from it.
The X-ray flux then emits from the STRUCK target media, typically Palladium, but there are several other metals that are used as E-beam targets for X-ray generation. ALL utilizing DC E-beam streams.
Even a TV electron gun is a DC device! Have that hit a polished palladium ingot at a 45 angle of incidence, and you get an X-ray flux emission from it.
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On 5/10/07 6:32 PM, in article snipped-for-privacy@4ax.com, "The Great Attractor"

These days, best practice is to drive x-ray TUBES with dc that is probably filtered some. X-ray equipment is almost always run from ac lines.
Although I do not know the history, I would be very surprised if some x-ray tubes were NOT run on ac. It is no trick to apply ac and have the tube be its own rectifier. The hardness of outputduring the cycle.
It was common practice for some radio transmitters to be operated with unrectified ac because of low cost. It was outlawed by treaty because of interference. Also, good operators could not receive as well with the rough tones.
Bill -- Fermez le Bush--about two years to go.
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Are you sure that you are not the Great Repeller? You surely repel me.
Bill -- Fermez le Bush--about two years to go.
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---------------------------- "The Great Attractor"
remove the X to answer
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BULLSHIT!
That's not what he said AT ALL.
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No shit?
I would never have known what the word RIPPLE referred to without your special inside info.
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They are external. They are specifically made for each type of tube used. Some have 15 volt filaments, some have 6.3. Some have variable filament voltages.
We were contracted to make a supply originally Mfgd by ECG for the airport X-ray units. Both OURS as well as ECGs were SEPERATE units, NOT integral... totally INTEGRATED third party devices!
Theirs had a lead lined steel box, and an oil overflow recovery vessel.
Ours had a BRASS tank and a recovery vessel. BOTH were separate generation driver stages, and in the box was the final multipliers, and transformers for the final DC outputs, all in oil bath, along with the tube itself. The flux exited through a fiberglass wedge and got focused by a huge Aluminum lens, which diffracts X-rays.
That was a nine inch long, 2.5 inch diameter tube that was $900 each. It was made by a famous German doctor that now only makes X-ray tubes. The target was Palladium, and ingot that was around 20 grams in weight.
The supply we made for LANL was ALSO a custom, built to order replacement for an existing setup. They sent us the tube, and we made the supply for it. It is currently being used to examine nuke warheads for long term aging viability specs. That was 50kV.
We also made supplies for a gas pipe inspection device made in Boston, IIRC. It was 4kV, and had a ripple of 0.00006% and was a DC to DC converter.
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No. That is exactly what he said. He even said that "rectified AC could be used to directly feed the tube".
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Bullshit.
The airport unit was a box that measured over two feet by one and a half feet by nine inches thick, and weighed over 90 Lbs. WITHOUT the oil.
The driver was external to that.
The 50kV unit for LANL was 50W, IIRC, and we even made one unit that was a half rack at 50kV 250W.
The gas pipe unit was a little bigger than a pack of cigarettes.
So three out of four of those were bigger than any unit you or he ever saw in any hospital or chip x-ray station.
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"The Great Attractor"
remove the X to answer ---------------------------- saw in any hospital or chip x-ray station.
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On 5/10/07 10:06 PM, in article rRS0i.175492$aG1.27529@pd7urf3no, "Don

Ask about the efficiency of converting that 250W into x-ray power. That number will make most electronic equipment look as if they were thermodynamic marvels.
Bill -- Fermez le Bush--about two years to go.
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You're a dope. We aren't talking about power distribution systems here, we are talking about X-ray machines.
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wrote:

What part of DC *IS* what results from rectified HV AC do you not understand?
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wrote:

My memory from working in manufacturing a long time ago is that 3 phase motors were very easy to reverse -- just switch any two wires.
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On 5/10/07 6:03 PM, in article %hP0i.41$ snipped-for-privacy@bignews2.bellsouth.net, "The

That is also true for two phase if you switch the two hots. Two phase was not as efficient in the use of materials.
Bill -- Fermez le Bush--about two years to go.
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Instantaneous 120 hertz power components cancel out - for large motors or generators real power is a constant - that's why motors over a certain size are almost always three phase.
Janet K.
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