[time-nuts] High voltage supplies

John Green wpxs472 at gmail.com
Mon Jan 18 16:52:52 UTC 2010


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.


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