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RE: Three phase electrons

To: "shop-talk@Autox.Team.Net" <shop-talk@Autox.Team.Net>
Subject: RE: Three phase electrons
From: Mark Miller <markm@tutsys.com>
Date: Mon, 10 Mar 1997 11:28:51 -0800
>>From:         Dunst, Mordecai[SMTP:mdunst@smtplink.coh.org]
>>Can someone give me a simple clear explanation of 3phase electricity?

It's easier with a graph but bear with me.  Imagine single phase AC as a 
sine wave, centered around 0 volts.  It climbs up to a maximum, then 
returns to 0 volts and drops to its most negative.  The peaks are at +/-177 
Volts giving an average of 110 VAC (more or less).
2 phase AC (in most houses with 220 service) consists of two such sine 
waves, 180 degrees out of phase with each other.  Each wave referenced to 
ground would be at 177V max (110 VAC average), but they are 'mirror' images 
of each other and if you look between the two the average would be 220 VAC 
(both are zero V at the same time, then one climbs to its maximum while the 
other climbs down to its most negative). It looks like a bunch of ellipses, 
peaks and troughs each at 177 V, and double that if you were to measure 
from a peak to a trough.
3 phase is three such sine waves, each 120 degrees out of phase with the 
others.  Because they are out of phase they don't add directly or cancel 
each other out; the result is something in between.  In this case, a 208 
VAC wave.
I have a simple excel graph that shows this, but don't want to post it to 
the list as it is 40Kb.  Anyone who wants it, let me know.

Mark Miller


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