.... IMO, key to understanding this and most other aspects of rotary phase
converters is to get past thinking of them as generators ...


Fitch tried an RPC as a generator [ * ] and it didn't work.

Which perhaps should come as no surprise.

If the idler was a "wound rotor, separately excited" machine, it would have
worked, however.

[ * ] By applying power to the star-connected 240 volt windings, and trying to
withdraw power from the 480 volt windings, which would normally be connected in
parallel with the other windings in 240 volt mode.