I worked for a brief spell for a company that made transformers. We had several high voltage parts and I came to appreciate making high voltage stuff is as much an art as a science. One of our products was a 7 kV ferro. The usual way to test one was to grab the silicone output lead and get it near the frame to see how far it would arc. We stress tested them at 10 kV for 24 hours by running the frequency at around 70 Hz. You would get a nasty surprise if there was a pinhole in the insulation of that silicone wire. They were vacuum potted in epoxy and you could tell when the vacuum pump wasn't pulling enough vacuum. All the parts would fail in a couple of hours. I don't remember the exact vacuum but it was extremely low. Another product went into electric fence chargers. Our customer had gone through literally dozens of transformer people before he tried ours. He said that after going to our parts, excepting lightning, he had not had a single field failure. There was a lot of stuff about high voltage I though counter intuitive but I learned the hard way that what works with high voltage doesn't always make sense. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.