Re: Single vs Two Phase (was - Spark gap erosion resistance)

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

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

Tesla list wrote:
 
> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>
 
> Tesla list wrote:

> > Original poster: "Wall Richard Wayne by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <rwall-at-ix-dot-netcom-dot-com>

> > John.

> > Sorry, but standard 220 vac comes in both two and three phases from the
> > electrical utilities.  The two phase system is 180 degrees apart and three
> > phase of course is 120 degrees apart in phase.
> >
> > RWW

>         WRONG AGAIN.  The normal

	US

> residential installation is a three-wire, SINGLE-PHASE system.  (In
> effect, a center-tapped single-phase system.)  A true two-phase system
> has voltages which are 90 degrees apart.  This definition has used
> since at least Tesla's time, and probably earlier.

	Mostly.

	Tesla INVENTED two phase/90degree.
	He later realized three phase was better (less copper for the
	same loss abd delivered power.)
	
	Most US home distribution is 'center tapped' single phase.
	(cf below)
	SOMETIMES, the power company delivers two of the three phases,
	so the home gets 120/208, three wire, two phase at 120 degrees.
	Uncommon, but it happens.

	(below)
	Whether the common 'centertapped 240' is single phase, or
	two phase, 180 apart always starts an argument.  Depends on
	how one measures.  If one measures relative to the neutral,
	the hot wires are shown as 180 apart, as can be seen on the
	scope.  BUT!  The 240 load is connected end to end.  The only
	way for THAT to see its 240 is for the whole thing to be
	IN PHASE.

	best
	dwp