Power Trans Question

[martin manning]

This is what you were after, though, eh? Reading a value from a graph is so last-century, like back when I was a lad.

[Reeltarded]

I like static things. Graphs and charts. I am the old guy on the porch. You kids get out of my yard.

[VacuumVoodoo]

Duguid used a factor of four on primary resistance, stating that a 220VAC winding would have twice the wire length and half the wire cross section.

This is correct in the case of switching wire diameters, which isn't always the case. What about multitap primary 100,120,220,230,240 - would you wind it using 1, 2 or 3 wire diameters?
IMO core cross section area of center column is the best indicator of power handling for common EI and C cores.
P[Watt]=Area [cm²]xT for 50-60Hz it will give a ballpark figure.
where T is max allowed magnetic flux density in the core, usually 1.2 Tesla for EI or C cores up to 1.5 Tesla for toroids.