[geeks] D'OH!

[Greg A. Woods]

[ On Friday, February 1, 2002 at 22:02:54 (-0500), Dave McGuire wrote: ]
> Subject: Re: [geeks] D'OH!
>
>   Electrician's trade terminology aside, in my example above, hot1 and
> hot2 are 180 degrees apart in phase.  That counts as two distinctly
> different phases by my fingers.  After all, electricians rarely even
> pull up their damn pants.

Well, yes, of course, but in terms of the distribution system it's a
single-phase system -- you never take the three-wire connection all the
way to any equipment, you either use the full winding or half the
winding for any given circuit.  If you want two phases with 180 degrees
of separation inside any equipment (eg. for a full-wave rectifier), then
you put a centre-tapped transformer in that equipment.

The only time it ever matters is when you have poorly designed and
poorly isolated equipment that in some way uses the AC signal for
timing, and then you try to integrate two such pieces of equipment that
are on separate circuits on separate sides of mains winding.  I've seen
this happen in larger television mobile units which require multiple 15A
power circuits, for example.

-- 
								Greg A. Woods

+1 416 218-0098;  <gwoods at acm.org>;  <g.a.woods at ieee.org>;  <woods at robohack.ca>
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