x-ray transformer reoiling suggestions
Eric Cannon
in oil to operate properly. I plan on perhaps making a Jacob's ladder or
throwing a few sparks around with it. I already have a heavy ballast to
current limit it for that purpose. However, I am not sure how to re-oil it.
I recently acquired a rather large PVC junction box that the transformer
fits into with some room to spare. I was thinking of using this box as a
housing and for the oil. Questions are: 1) Is a re-oiling possible and will
I be able to obtain up to, say, 70% of output? The transformer is split so
when it operated, there was +/-45 KV on each side. 2) What type of oil
should I use? Obviously, probably transformer oil, but it seems difficult
to obtain. Can mineral oil be used instead?
Thanks,
Eric
Bert Hickman
Hi Eric,
The PVC housing should be fine as long as it is oil-tight. Mineral oil
will slowly seep out of any cracks or unsealed seams.
You preferably want to use transformer oil. For your application, it
doesn't matter whether you use inhibited or non-inhibited oil. Some
manufacturers and types that will work include:
Shell Diala-X, AX, M, MX, or HFX (fire resistant)
Exxon Univolt N 61 B
Cooper Edisol TR or Envirotemp FR3
Esso Voltesso 35
Mobilect 35 or 45
Contact oil suppliers in your area to see if they carry any of the above
products. You can also contact your local electric power company to see
if they might give/sell you some - they use it by the tanker car full.
Another alternative are companies that maintain x-ray equipment.
Although most transformer oils are highly refined, filtered, and dried
mineral oil, many newer transformer oils are vegetable oil or soy-based,
such as Cooper's Envirotemp FR3.
In a pinch, you can use unscented USP white mineral oil from drugstore
or veterinary supply store or non-formulary (NF) industrial white
mineral oil. However, these may contain a small amount of water, and you
may not be able to apply as much voltage stress as with dried
transformer oil.
Remove any accumulated dust and dirt from the transformer using a paint
brush and kerosene or mineral spirits, and let it dry. Then immerse your
transformer in the oil for several days. Rap the side of the tank or
transformer core periodically to dislodge any air bubbles that work
their way out from the windings.
You can then carefully power up the unit using your ballast and a variac
and slowly increase the voltage, looking for any abnormal behavior
(arcing, bubble formation, or bluish glows). Assuming the transformer
was not damaged, you should eventually be able to use it to its full
potential.
Bert
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