Matt BlazeRotary Converter, IRT Subway Substation 13, NYC, 2017.
High voltage pixels at https://www.flickr.com/photos/mattblaze/32992380451
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 via a number of substations throughout the city, where high voltage AC is converted to the lower voltage DC used by trains.
Until recently, this was done with electromechanical rotary converters (essentially a combination AC motor and DC generator). They have been supplanted by solid state rectifiers, but a few of the original rotary converters remain operational.
Space Hobo@mattblaze For a while between the two technologies, there were some mercury vapour rectifiers, which are the most Mad Scientist-looking devices ever.
@spacehobo Yeah. I think the subway skipped over those. Mercury vapor rectifiers definitely have a mad scientist vibe.
Phil Stevens 
@mattblaze @spacehobo The 1.2 GW DC link between our main islands used to have mercury rectifiers at either end. Now the job is handled by thyristors.
Dr. Eric J. Fielding, PhD@mattblaze It is amazing that 120-year-old technology with many moving parts can last that long.
vxo@mattblaze I bet that big chunky handwheel there went to a clutch that engaged or disengaged a separate startup motor that got the AC motor turning before field and rotor current were brought up in a very hands-on, steampunk, seat of the pants, high stakes looking procedure.
I've seen YouTube videos of this...
@mattblaze OH this isn't the video I was looking for yet but hooooooooly moly that's blissful.
Not sure I really call it a classic ASMR response or anything, but this stimulates the good chemicals in my brain.
Watch the initial start-up of a 1915 vintage 750 HP (560 kW) motor #shorts #youtubeshorts
@mattblaze Here's the steampunk summoning ritual. https://www.youtube.com/watch?v=fNuI6keQXYA
Synchronous motor start 350 HP 2400 volt
@mattblaze oh I forgot, this one doesn't use a pony motor to start it, it just lets the entire housing spin free then gradually load up the output using the brake. It's a hilarious but effective approach. Just let it do a cartoon slipping run (to be accompanied by rapid bongo drumming)
Blort™ 🐀Ⓥ🥋☣️Beautiful.
Sir Osis of Liver 🇨🇦 🇲🇽It's surprising how long those things lingered on.
When the Grand Falls (commissioned in 1931, 66MW) generating station in NB flooded in 2008, that was the final straw for the rotary exciters.
They could have been rebuilt, but the decision was made to upgrade to ABB static exciters. They also took the opportunity to install them at a higher elevation in the plant to minimize the chance they got submerged again.