Need a little experiment carried out....

[Jonathan]

Hmmmm hadn't though about that. Should be powering both windings in parallel then?

If we're just using it as a load, since it doesn't look like we can get useful information from the other phase, then yes I tend to agree. Also you wouldn't get rated power with just one phase energized.

Maybe, but a dropping weight and pulley is easy to calibrate

Yep, could even use dropping a weight to calibrate the other system.