Quote:
Originally Posted by trinescope
Thanks a lot for the information! I was thinking of thinning the varnish with mineral spirits so it would be thin enough to get inside the windings and insulation. I first need to find a suitable tape for winding layer insulation. I used Kapton the first time around, but it's a bit pricey, has to be ordered in, and wires just slide all over it easily. Masking tape is too thick (5 mil), so I need to use something like regular old Scotch tape. The secondary is the tricky part since it carries 3KV or so of DC and up to 1KV of AC on top of that, and that's in very thin 41AWG wire.
I already have the equipment for doing the impregnation, just need to try again. I really didn't pull a vacuum as long as I needed to since the resin I used had a relatively short work time and I didn't want to end up with a big block of resin with a transformer in it.
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Rather than thinning the varnish, try pre-heating it to reduce viscocity, and also making sure the transformer is well heated to expel moisture. Read through the procedure I linked to, the steps and heating were all based on trial and error - I tried a bunch of iterations to get to that. Long working time of varnish is a good thing. After you're done, unused varnish can be put back into the can and used later.
As for wires sliding all over kapton, why not use something like spray on 3M adhesive to make it a little bit tacky before installing it? Just a light dusting should be enough to hold the wires in place.