you are correct. it is perfectly safe to use dual primaries (or secondaries) for isolation. The wire is triple-coated with enamel, plastic and another layer of enamel.
While I have a multi-thousand dollar Topaz 10kVA Ultra-isolator on my development bench, we require something cheaper for production testing of our inductin heaters. Dual primary dry type transformers fill the bill just fine. Each new transformer is HiPotted at 2500 volts winding to winding for 10 minutes before being put into service. Never had one fail. John On 10/01/2015 12:14 AM, gregebert wrote: > I did some research on UL/CSA approved transformers, and there is a > requirement that all windings withstand a minimum breakdown voltage, even > if they are intended to be connected together, such as dual-primaries. > Depending upon the VA rating and the voltage, the breakdown must be between > 1050 and 4000 V RMS according to how I read the spec (UL5058-2 / CSA C22.2 > #66). The test is conducted between 1 winding, and all other windings and > the core combined and at elevated temperature. There are copies of the spec > online. > > I knew there had to be some amount of isolation, but I did not realize it > was *that* high. While I would never expose or touch anything that is > supposedly "isolated", it does reassure me there is decent insulation. > > -- John DeArmond Tellico Plains, Occupied TN http://www.fluxeon.com <-- THE source for induction heaters http://www.neon-john.com <-- email from here http://www.johndearmond.com <-- Best damned Blog on the net https://www.etsy.com/shop/BarbraJoanOriginals <-- please visit PGP key: wwwkeys.pgp.net: BCB68D77 -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/560D7562.7010100%40neon-john.com. For more options, visit https://groups.google.com/d/optout.
