It all works out well! The generators have to be derated 20% to compensate for core saturation at 50Hz, but the 20% lower voltage perfectly offsets it. If the coils are designed to handle full rated power at 208V (taps in parallel), they are generally sufficient for full rated power at 400V (taps in series) as well. There may be some derating for some equipment, though.
I don't want to switch to 50Hz, though- that's moving backwards; all our transformers and motors would need derated for saturation and it defeats the purpose of going with a higher voltage for lower costs. What we need is a compromise- 230Y/400V 60Hz for all
