Re: IS 240VAC two-phase - NO

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

Original poster: "Jolyon Cox" <jolyon-at-vatercox.freeserve.co.uk> 

Technically 180 degrees apart is in "antiphase" with the two waveforms
reaching equal but opposite maxima simultaneously.

Assuming a criterion whereby it is assumed the sum of all the angles between
phases must add up to 360 degrees
then, if the the succesive phases were 90 degrees apart, this would in fact
result in a "four-phase" supply  with phases "balanced" at 0, 90, 180 and
270 degrees around an imaginary circle; effectively this would be the same
as a pair of two phase (90 degree)  supplies connected in antiphase, as the
third and and
fourth phases  would be 180 degrees out of phase with the first and second
phases respectively.

Four phase supplies are apparently not too common, the
principle  exception being for stepper motors in computer applications,
however the "balancing" of phases is an essential part of power distribution
practise, as it eliminates pulsations in torque in generators and motors,
enabling smoooth running and reduced wear on moving parts.

As to the benefits of three-phase transmission over
single-phase,"quadrature" (i.e. two or four phase at 90 degrees) or a higher
number of phases it seems that the best explanation for
the adoption of the three-phase format over the possible alternatives is
economic, since a supply of  3 phases, 120 degrees apart is the minimum
acceptable to start and run polyphase AC motors with constant torque.

Jolyon.


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, January 10, 2004 7:15 PM
Subject: Re: IS 240VAC two-phase - NO


 > Original poster: robert & june heidlebaugh <rheidlebaugh-at-desertgate-dot-com>
 >
 > While it is quite rare this day some rural power companies such as Wells
 > Nevada rural power co. still has 220 volt 2 phase supplied to the public.
It
 > causes no problems except with phase sensitive laboratory equipment. When
I
 > used  thier power I was more than willing to put up with the small problem
 > with the low cost of power as compaired to power cost of 3x in utah.
 >             Robert   H
 > --
 >
 >
 >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  > Date: Fri, 09 Jan 2004 20:15:32 -0700
 >  > To: tesla-at-pupman-dot-com
 >  > Subject: Re: IS 240VAC two-phase - NO
 >  > Resent-From: tesla-at-pupman-dot-com
 >  > Resent-Date: Fri, 9 Jan 2004 20:37:59 -0700
 >  >
 >  > Original poster: dave pierson <davep-at-quik-dot-com>
 >  >
 >  >
 >  >> I was quite amazed that quadrature phasing was not
 >  >> developed.
 >  >
 >  > Three phase/120 moves more power for less copper andless
 >  > loss than 2phase 90.
 >  >
 >  > Or so the textbooks demonstrated in school.   That was
 >  > 40 odd years ago:  the texts (and maths details) are long
 >  > since lost.  The prevalence of the three phase/120 system
 >  > demonstrates its benefits...
 >  >
 >  > I dunno if current texts go into the benefits...
 >  >
 >  > best
 >  > dwp
 >  >
 >  >
 >  >
 >
 >
 >