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Re: Dry pole pigs
>
> How far is a pole xfmr de-rated (Vsec and W)
> if it is de-canned, and operated dry?
> -GL
> www.lod-dot-org
Total guesses, but here goes...
I would expect that the voltage rating would be comparable, because the
original designer had to assume that there would be turns touching without
any separating oil. The winding to core rating might be less, since the
designer probably figured on oil soaked paper or cardboard there.
As for heat, the ratings would be a whole lot less. Not only is air a lot
less dense than oil, but there isn't a way for it to circulate.
However, I would suggest just testing. Do a partial discharge breakdown
test for the voltage rating (most HV texts describe how it's done, but
basically, you gradually ramp up your exciting voltage and look for the
high frequency from the corona resulting from incipient breakdown). And,
for power dissipation, measure the temperature of the windings by measuring
the resistance like they do for AC motors, or, with an educated guess,
stick a fine wire thermocouple into the winding somewhere.
You could put it "dry" into a pressure tank and run it in dry nitrogen,
SF6, Freon, or hydrogen, also. The tank might be heavy, but at least, you
wouldn't have the weight of the oil.