Matt Blaze on Nostr: The IRT subway in NYC, opened in 1904, uses a 600 volt DC third rail running ...
The IRT subway in NYC, opened in 1904, uses a 600 volt DC third rail running alongside the tracks to power the trains. Power is fed to the system by a number of substations throughout the city, where AC mains power is converted to DC. Until recently, this was done by electromechanical rotary converters (essentially a combination AC motor and DC generator). These were (surprisingly recently) replaced by solid state rectifiers, but a few of the rotary converters remain operational.