Yes, odd harmonic currents are additive on a shared neutral when more than one phase is involved. I have read that on 3-phase feeders supplying HID lighting with say 100 amps on each leg, the neutral current may be as high as 140 amps!Now I know what the say about harmonics theoreticaly but I would like some input practically
I have heard rumors that it buned holes in cabinets in ny state and elswhere I have also heard that if you put a neutral with each circuit that this will eliminate them
Mabe we can get some input from overseas. GB Nor etc.
This occurs with fluorescent as well, and computer equipment. Pretty much anything with an electronic switching power supply. You can either over-size the neutral, so called "super neutrals", or use a separate neutral for each leg. As far as pipe fill goes, whether you use a super neutral or three individual neutrals, they are considered current carrying.