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
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.
such a handy thing for high-power coilers to know how to do.