On Sun, 8 Aug 2010 14:30:10 -0400, Bert Almemo wrote:
>I dont' understand how anyone can argue against a 3-phase electrical
>distribution system. The modern part of the world has been using it for many
>decades
>>"NO good reason to have 3-phase power...?"
Ah, the joys of selective editing (or listening). Just like Fox News.
What the quotation left out after the dot dot dot dot was EXCEPT FOR RUNNING
BIG MOTORS. Further, I was not talking about DISTRIBUTION, I was talking
about the INTERIOR WIRING OF A RESIDENCE.
>and there is proof it's a better system. If you also put it
>underground in urban areas it's safer and has less problems.
If you read my original post on the topic, I described a MAJOR SAFETY PROBLEM
associated with 3-phase power -- HARMONIC CURRENT IN THE NEUTRAL, and
CIRCULATING HARMONIC CURRENT IN DELTA CONFIGURATIONS. This problem is VERY
well known, except, perhaps, by hams. Ever hear of the Towering Inferno? That
was a combination of harmonic current and flammable insulation. UL was
quickly revised to control the insulation used on wiring in buildings, the
definition of Power Factor was revised to include harmonic current, and
engineers started paying a lot more attention it when they designed
electrical systems for buildings.
Three phase power exists primarily for two reasons. 1) That's how nearly all
power is generated -- with 3-phase generators. 2) It is a far more efficient
way to RUN a motor. The harmonic problem makes it less desirable for any
system that draws non-sinusoidal current, which is virtually anything with a
power supply in it.
If you care to differ with me on this, go back and read the original post,
not on some poorly edited sound bite version of what I said. Like Fox News.
73, Jim Brown K9YC
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