Since Mulv has extensive experience with USA style power...
We have 60 cycle 110-120 - 115 v average single phase supply that covers about 90% of domestic items 2 or 3 wire ground dependant
We have 220-240v dual phase / neutral for things like welders and clothes dryers.. 3 wire
We have 220-240 3 phase / ground for large electric motors that are phase wound like in large computer discs and trolly cars 4 wire
We have 380 v Y connected for some office lamps
We have 415 delta connected for more efficient office lighting..
Just assume that any item of low current will be 115 and any item of high current will be 220
Now it is clear, yes?
Cheers
Mulv