Feels like it's both to me. 3 phase, 3 wires is optimal for the amount of conductor material needed to distribute it. But it's also optimal for motors for a f

Feels like it's both to me. 3 phase, 3 wires is optimal for the amount of conductor material needed to distribute it. But it's also optimal for motors for a few reasons. Easy to reverse direction of the motor, self starting without a capacitor, and higher overall power and efficiency.