The only real way to get 3 phase power from your single phase power source is to use a phase converter. The only ones that I am aware of that are efficient enough, and large enough to handle the power requirements of a Powermax1650 are rotary phase converters. Here is a link to a website that sells them and seems to offer advice and a lot of info about how they operate.
3 Phase Converter Info- Sales- rotary phase converter, static 3 phase rotary converters.
From my exerience with larger industrial plasma systems..the Phase converter needs to be sized to handle approximately 150 to 200% of the power requirements listed on the nameplate for the plasma system. This means the phase converter would have to be pretty large, and probably quite expensive...
You may be better off selling the 1650 and getting a a plasma system that will operate on your single phase power. The Powermax1250 or Powermax85 are both capable of heavy cutting (the 85 has almost the same capability as the 1650) on single phase power.
Jim Colt Hypertherm