Before connecting to 230VAC, add two 100 w light bulbs in series with the
primary to control any runaway current suggested by Tom. Otherwise, same
test as suggested before. If a digi MM is handy, measure AC v across
primary when the bulbs dim to estimate secondary "test" voltage.
How now?
I had in mind a 1 amp fuse, but didn't specify value. If core saturates,
fuse blows, no problem(?)
Jerry W4UK
At 05:38 AM 12/16/2001 -0800, 2 wrote:
> >
> >
> >> A quick&dirty test of the insulation might be to simply connect the
> >> (fused) unloaded xfmr's primary to 220 briefly to see if it can stand
> >> twice the voltage it will see when you actually use it. Then lift the
> >> secondary winding from ground, ground the other end and re-test to
> >> verify the insulation at both ends.
> >
> >Woah there! Don't do that!
> >
> >Most efficient transformers are designed to run with the core near
> >saturation. Very few would have safety factor of 2x.
> > ... ...
>// Most of the transformers I've tested begin to saturate at c. 20%
>overvoltage. 100% overvoltage is unreasonable. The best insulation test
>is with a high-pot tester.
>- To see when the core is getting near saturation, unload the
>secondaries, slowly increase primary potential and watch primary current.
> When pri. current begins to increase substantially, saturation is
>happening.
>- To improve transformer insulation, pot the transformer with
>(polyester) fiberglass laminating resin. Potting can be done in one's
>workshop for low cost. Info on insulation/potting is on my my Web site.
> See "Amplifiers" - Part 3.
>
>cheers
>
>- R. L. Measures,
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