"Bill" wrote in message
...
Also when you have a building which has a 3 phase service, a lot of the
stuff is not 3 phase - lighting, 120 V outlets, etc. So you want to
balance
the load in the panel. Some circuits will be on one phase, others on the
next, and the rest on the third.

So this is why you might see three big huge wires and a little teeny tiny
4th wire for a 3 phase business electrical service. Most of the load is
balanced between the 3 phases.

Same as with a house where you want half on one leg and the other half on
the other leg.

I doubt that you would see a building that has 120 V outlets and a tiny
return. Too much of a chance of loading one phase.

But when the loads are hard wired to 3 phase the return can be small or not
in existance. I remember one military application where the power was a
grounded delta.



FYI - Connecting the wires on an electric motor for 3 phase can be complex
to say the least, as there are different types of 3 phase service. Scroll
down to "Three Phase Motors-Single Speed" on the following link...
http://www.patchn.com/motor_connections.htm