Y nutral wire size for unbalanced loads.
Y nutral wire size for unbalanced loads.
(OP)
I have been told that in a 3 phase Y lighting panel that the nutral must be larger than the phase wires because of the possible imbalance of the loads. The worst unbalance I can think of would be to have one phase to nutral loaded and the other phases with no load!? That would provide the same current in the nutral as the phase. It seemes any other combination would be less in the nutral!? What am I missing?






RE: Y nutral wire size for unbalanced loads.
RE: Y nutral wire size for unbalanced loads.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Y nutral wire size for unbalanced loads.
In theory, if you have 100% 3rd harmonic load, the N current could approach 1.73 times the phase current in a balanced three phase system.
On the other hand, if the lighting panel is oversized to begin with you may not need to oversize the neutral of the panel or its feeder neutral.
For example, you have a 200A panel which feeds 80A of lighting load it may be a non-issue. I am yet to see a fully loaded lighting panel. But again, you need to make the decision based on your system conditions.
RE: Y nutral wire size for unbalanced loads.
Now it makes more sense. Thanks for the insight!