Wednesday, November 21, 2012

DC power grid still runs in San Francisco

DC Elevator Motor
Fascinating bit of techno-history persisting in the modern day.

http://spectrum.ieee.org/energy/the-smarter-grid/san-franciscos-secret-dc-grid .
In the early days (ca 1920) some hams could run their radios with the "B+" (plate voltage) coming straight from the DC power mains, saving money on expensive power supplies.  But if you needed high voltage for your transmitter's final, you might have needed a motor-generator (dynamotor). That would have been a big expense compared with an AC transformer/rectifier.
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