The pump has a separate box that has an electronic 3 phase converter in it. The 3 "normal" 220v wires (2 hot & a grounded) get used/coverted to 3 hot wires in 3 phase. Of course, the motor is a 3 phase motor as well. The whole thing comes as a "system". The Pentair Intellipumps are based on the same prinicipal/engineering. One change is that you can't use a 220V GFI breaker anymore because the GFI always sees a differential to ground and pops.
The 220V single phase goes to the converter box, which changes it to 3-phase. Once it is 3 phase, you can control the motor speed easily by changing the cycle, anywhere from 0 (in theory) to 60Hz. All of this is done in a nice, pool ready package. The pump I have has 4 speed settings, but you can really only use 3 of them due to the controlling switch. The new models this year give you access to all 4 settings. I really only use 2 of the speeds - low speed for normal running (virtually silent) and "boost" for solar (runs at 55 hz, so about 90% of full speed for the pump). I have the "high" setting running at about 65% of full pump speed for when I want to get a little more circulation going (say after a party or heavy rain). According to the provided charts, low speed (as I have it set) uses about 1/4 of the electricity compared to high speed while providing about 1/2 of the flow.
The guy that installed my solar has a "real" job as a commercial power engineer (large backup generators and power systems for schools, mainly). He said the system was very similar, though much smaller, to commerical A/C and heating systems that he installs and inspects.
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