Re: Repost RE: Explain 3 Phase

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "davep by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davep-at-quik-dot-com>

Tesla list wrote:

> Original poster: "Peter Lawrence by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>
 
> Dave,
>      I think I finally see where you are comming from...
 
> You might be (implicitly) drawing an analogy with DC batteries, which when
> connected in series are always all lined up the "same way" to give a higher
> output voltage.

	A perfectly valid way of putting it.
 
> You might be thinking "DC same way" is analogous to "AC in phase" so you
> think "in phase" is the correct way to describe 240v service.

	It is.  If the outer lines were out of phase, there would be zero,
	rather than 240VAC.
 
> So my conclusion is you are talking about how the AC is generated, whereas
> the rest of us are talking about what we measure (on the three wires involved
> with 240v service) thinking of the generation as a "black box" not to be
> opened.

	Measurements must be made with a phase sensitive & floating
	instrument (eg not a common, one side grounded scope....)

> We are measuring relative to ground because that is "standard practice", and
> in that sense the two hot wires of 240 are two 120vac 180-degrees out of
phase.

	...and yet, if i connect a load from one leg to another, i GET
	240VAC.  (And the only reason for having them is to connect a load
	to...

	(and, as i noted, the parallel/analogy to DC IS exact: Edison
	(yeah.  Him...) invented that system, in some older
	texts, both the AC and DC versions are referred to as
	'Edison System'.  (One may suggest this naming is in apropos,
	and i'd tend to agree.  The comparison is, however, apt...))

	best
	dwp
	(who really here endeth...)