by JonR10 on Wed Jun 01, 2011 2:26 pm
Single phase 220V generally uses three wires (two "hot" and one ground).
Three-phase power requires 4 wires (three "hot" and one ground)
A three-phase connection may actually have 5 wires (three "hot", one ground, and one neutral).
The neutral wire is optional...
See this :
http://www.3phasepower.org/3phasewiring.htm
Jon Rosenthal
Houston, Texas