AdrianW

True 2 phase systems with a 90 degree phase angle were never popular in the UK and are probably now extinct.

 

Used to be a bit more popular in the USA but now rare. As an historical note, the large hydroelectric plant at Niagara falls originally produced 2 phase, and at 25 cycles rather than the more common 60 cycles. Lower frequencies used to be favoured for electric motors including railways. In Belgium they still use 16.66 cycles for some railways. Frequencies of less than 50 cycles are unsuitable for lighting, especially d0m3sticaly.

Isn't the channel tunnel "2-phase" using Scott transformers? I remember reading an article in the IEE mag (as it was then) about the power supply arrangements & I'm sure I read that it utilised the Scott configuration to derive the supply to the two running lines.