Re: Single vs Two Phase

["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: "Alex Crow by way of Terry Fritz
><twftesla-at-qwest-dot-net>" <alexcrow-at-blueyonder.co.uk>
 
> Hi all,
 
> I would say from my reading of various ham radio and RF design texts that the
> two 'hots' in a 240v system (with the centre being neutral, and if this is
> really how it works in the US) are 180 degrees out of phase,

	Only from the neutral.

> relative to some DC reference voltage, so that at any point in time
> the voltage between them is twice that between each leg and neutral

	If 180 out, the sum is zero.

> (which is the 'zero crossing' for both waveforms). I see it like this
> (sorry, ASCII art was never my strong point)-

	Nicely done.


>        _      +120
>       / \
> Hot1 |---|-------0
>          \_/  -120
> 
>           _   +120
>          / \
> Hot2 |---|-------0
>       \_/     -120
> 

	Indeed.  Now ADD them.  Point by point.
	They add to zero.  Which is NOT what is present from
	line to line in 140 v system...  The 180-ness is an artifact
	of using a grounded scope...  Use differential probes...
	Or two single ended probes and the summing function of
	the scope.

	(Historical Hint:
	This system was originally developed by Edison (or his
	engineers) to deliver higher voltage, without transformers.
	They did it on DC.  Try modeling it, mentally, with DC....)

	best
	dwp