Three phase and IBM

Brent Hilpert hilpert at cs.ubc.ca
Sun Mar 20 14:15:00 CDT 2011


On 2011 Mar 20, at 12:43 AM, Eric Smith wrote:
>
> That seems far more sensible than the 120/240V "split-phase" wiring 
> used in residential and light business here in the US.  I assume that 
> we use split-phase because putting a single-phase transformer on the 
> power pole is less expensive than a three-phase transformer.  It's 
> also stupid that we use such a low voltage; it means that only a few 
> outlets in a US house are wired for 240V, generally just the 
> stove/range, clothes dryer, central water heater, and furnace.  (Where 
> available, people use natural gas for those instead, as it costs 
> less.)  Electric kettles, room heaters, etc. have to run on 120V at 
> 15A or less, so they are very slow.

I suspect our 120/240V (also 110V,115V,117V) split-phase distribution 
is a legacy of the "War of the Currents" between Tesla/Westinghouse and 
Edison. When Westinghouse entered they presumably had some interest in 
compatibility for end-users and existing loads with Edison's early 
distribution system, which was 3-wire and conceptually similar: +110, 
-110V & neutral.




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