Originally Posted By: BRZED
Originally Posted By: CT8
They are grounded.
What does the pole ground wire connect to if there is no static wire?
Tesla worked out that with polyphase, the sum of the three phases, 120 degrees out of phase was zero.
So a balanced three phase system needs no return. If it's not balanced, the imaginary "zero" floats off in the direction.
But the imbalance is often returned to ground. Some have 4 pin 3 phase, some have 3 pin.
Allows some oddball things.
* motors can operate in "star" mode, phase to neutral (nominally 240 here)
* can be operated in "Delta mode", where it's phase to phase across the windings (nominally 415 volts here)...can have switching gear that starts "star", then moves to "delta"...like changing gears on runup.