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Re: [TCML] Dentist x ray trans question

On 7/5/16 10:16 AM, Bert Hickman wrote:
Hi Forrest,

If the unit was manufactured after 1979, it will not contain any PCB's.
And, some manufacturers, most notably GE, never used PCB's in ANY of
their X-ray machines. You can test a small sample of the oil - does it
smell/look like mineral oil and does it readily burn an oil-soaked piece
of paper? To know for sure, use a PCB testing kit. See:

Dental X-ray machines typically drive the X-ray tube from a 60 - 100
kVpeak source at 7 - 15 mA. This is NOT the continuous duty current
rating of your transformer - it cannot take this load continuously. The
short on-time and thermal mass prevents winding overheating in normal
X-ray supply usage. The X-ray energy (in keV) of an X-ray system is the
peak output voltage, so the RMS voltage of your dental X-ray transformer
will be in the range of about 40 - 70 kVRMS.

The other thing to know is whether it's line powered or if it's running off an inverter. I have a "portable" X-ray power supply (a wheeled cart) that runs the HV transformer off a 500 Hz square wave inverter.

I find that the output voltage on most X-ray transformers is awfully high to be generally useful: managing corona on 50kV circuity is a pain, although one can always run it at a lower voltage.

If you were building some form of high voltage pulse generator (Marx) then the Xray might be a good charging supply (with the right current limiting on the secondary) since you could get a decent stage voltage in the stack, so getting, say, 1 MV doesn't require 50 stages.

Or if you were doing some sort of fusion experiments where you need something in the 20-50kV at a few mA range.. a bit out of range of the typical NST, and inconvenient for a Cockroft-Walton multiplier (which would have terrible regulation). A primary controller on a big transformer with low output impedance might make a good stable supply for those sorts of experiments.

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