Matt Blaze on Nostr: NYC's IRT subway, opened in 1904, is powered by a 600 volt DC third rail running ...

NYC's IRT subway, opened in 1904, is powered by a 600 volt DC third rail running alongside the tracks. Power is fed to the system by a number of substations throughout the city, where high voltage AC power is converted to the lower voltage DC. Until surprisingly recently, this was done by electromechanical rotary converters (essentially a combination AC motor and DC generator). These have been supplanted by solid state rectifiers, but a few of the rotary converters remain operational.