G&M wrote:

I think you've been seeing too many good transformers. The cheap ****e
coming in from China nowadays has most loss due to saturation of the core -
your (ii) and (iii) above.

Not really, because the iron losses will flatten out as you reach
saturation. When the core is being driven into saturation the main
source of increased loss is copper loss in the primary, due to the
magnetising current shooting up.

Worse still it varies wildly from batch to batch.

Find yourself a better manufacturer. Nor everything cheap from China is
crap.

--
Andy