Thanks, yes apologies, its full so called "mains isolation", ie, must perform to the 3500VAC isolation hipot test.
Theres no dipping or varnishing for the windings. This would be too expensive for us.
Though for this question, as you know, isolation is not important to be known, because we are speaking of the primary coil alone here.
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..And..Ditto this question, but this time concerning a high side gate drive transformer for an offline 240vac two tran forward smps (as attached).
The attached shows that the secondary is two layers...we don't bother putting tape between those 2 secondary layers. Should we? What is the risk of getting a nick in the wire? We've managed fine so far, but we wonder if a "rough winder" does the job? Who knows?