Re: 3-phase current - you don't need caps or ider motors!

Date forwarded: 	Tue, 8 Dec 1998 14:01:11 -0700
Date sent:      	Tue, 08 Dec 1998 12:05:12 -0700
To:             	tesla-at-pupman-dot-com
Subject:        	Re: 3-phase current
Forwarded by:   	tesla-at-pupman-dot-com
From:           	Tesla List <tesla-at-pupman-dot-com>

> Original Poster: "mike" <mike-at-gmx-dot-com> 
> Hi Ed, all:
> I believe that some of these designs include an idler motor, as suggested
> in another post, to actually generate a third phase. This method produces
> more power than simply running a three phase motor on 1 phase, although
> probably not as much as true three phase power. The available power depends
> on the size of the idler.
> - Mike
> > 	These are just capacitor starting devices, and can't supply a
> > significant load.  The three phase motor runs single phase when started,
> > with a large loss in output power.  I run both my milling machine and my
> > lathe with such devices, and the torque "ain't what it used to be", but
> > still useful for light machining cuts.
> > 
> > Ed

I knew I had this somewhere, but it took me a while to find it.  There is a
to change 2 phase power to 3 phase using only two transformers!  It is 
called a Scott transformer, and was used by power companies to go from 2 
phase to 3 phase or 3 phase to 2 phase power.  You do not have the puny 
power limitations of capacitor systems, nor do you have to use a large 
motor/generator setup.  I found this in my 1939 Coyne home electrial 
course.  One transformer is centertapped, the other transformer has a tap 
placed at the 86.6% point.  I will place the schematic and text on my web 
page in the next day or two and I will notify the list when it's there.
This is 
such a handy thing for high-power coilers to know how to do.

Bert Pool