AC power alternates between positive and negative in regular 50Hz or 60Hz frequency. 3-phase 220v takes that concept and superimposes 3 sine waves on top of each other with a phase difference of 120 degrees. When you measure voltage on an AC line you are getting average or root mean square depending on how you measure it so voltage is actually higher than you measure and lower than you measure. This isn't always good for systems that need lots of power. Superimposing three sine waves keeps the voltage and current at a more constant level.
I'm impressed that GG made artificial 3 phase from a dryer plug. That is a trick and needs big components to do it.
If you have a big 1:1 transformer, you might be able to make a "wild leg" power source.
We cheated, this "dryer-outlet" is 3-phase with up to 200Amps behind-it @ 208V, (although we were using a 50amp-breaker).
But I have built a couple of phase convertors that would handle this, mostly just need a 3-phase "idler-motor" and some capacitor to make the "extra-leg".