On Wed, 22 Nov 2006 20:11:12 GMT, john smith wrote:

In article ,
"Peter Dohm" wrote:


180 degree out-of-phase" voltage level.

Are you certain you don't mean 120- or 240-degrees out of phase?

How does one get two lines 180-degrees out of phase?

240V single phase, commonly supplied to single family dwellings, has a
center tap and two hot leads which are 180 degrees out of phase to supply
higher powered items such as air conditioning and electric stoves. In
addition, approximately half of the lower powered items, such as lights and
the refrigerator, are powered by each of the two legs to the center
tap--which is approximately ground potential.

Ahhh! But where does the 240 come from?
Does it not come from two of the three legs of a Y or Delta?
These are square root and cube root functions.
If they were 180 out of phase, it would cancel.

In north american residential and in most cases rural electricity, the
220 is NOT derived from a delta or wye connected three phase, but from
a simple center tapped power transformer on a single phase line (or
one leg of a three phase line - not 2). 208 is derived from 3 phase,
and is only found in SOME buildings where 3 phase is required for
other purposes, such as multi-unit residential buildings with 3 phase
elevators, or commercial/industrial applications.
Even in many of these situations, a center tapped transformer (single
phase) is used to provide the 120/240 single phase domestic power.(at
least in Ontario Canada)

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