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From: grege@gold.gvg.tek.com (Greg Ebert)
Newsgroups: sci.electronics
Subject: Re: 1 phase to 3 phase conversion
Keywords: phase conversion
Message-ID: <2158@gold.gvg.tek.com>
Date: 8 Apr 91 18:55:05 GMT
References: <1991Mar28.191005.1653@rodan.acs.syr.edu> <3613@polari.UUCP> <4725@osc.COM>
Distribution: na
Organization: Grass Valley Group, Grass Valley, CA
Lines: 15

You can build a trivially simple 3 phase converter *IF*  (and that's a
very big IF) the building was improperly wired.

I used to live in a condo, and the '220' plug was actually two 120 VRMS
lines which were 120 degrees out-of-phase (which is why the votage was
208 VRMS and not 230-240 VRMS). This is easily determined with a
crummy voltmeter. Nope, you don't even need a scope.

The third phase can be reconstructed by using two 1:1 isolation transformers.
Basically you 'add' the two phases which you do have, then invert this sum.
Now you have 3 phase AC. I got 2 transformers at a surplus store which
were rated at 120V 20A / 240V 10A [now way dude, they aint for sale].

I gave my solid-state inverter a few years rest with the above setup, except
when I wanted to run 60 Hz motors at 330 Hz [boy do they scream !]