Can someone direct me to reading material on this?
Plug alert: My web site, of course... The articles on "transformers and
coils", and "practical transformer winding":
I've wound a HT transformer and it's got a decent hum to it
That hum typically comes from vibrating parts, specially the
laminations, and particularly the section of the laminations that's
inside the bobbin and thus somewhat hard to compress properly. Try
compressing the pack a bit harder, and use wedges to compress the part
inside the bobbin. If that doesn't kill the hum, you have to impregnate
the transformer. Get some transformer varnish, loosen up the core, soak
both the core and the winding assembly with as much varnish as you can
get in, then tighten the bolts of the core, insert wedges if possible to
compress the center leg, and let dry. Ideally heat it up to speed
drying. You can use DC through the high voltage winding to heat it up.
Roughly the nominal secondary current, or even a little more.
> and draws about 1A @230V input with no load.
That doesn't sound bad at all. That current is strongly phase-shifted
relative to the voltage. So the actual power consumed while idling (core
loss) is likely to be far lower than 230W. If it's a transformer for a
legal-limit amp, then this amount of idling current looks plenty low enough.
Do you have a true power meter? If so, you can measure how much of the
230VA is real power, and there you have the core loss - because
essentially all the real power taken up by a transformer when idling is
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