Hi, I haven't looked at cable calculations for a few years, and wondering if anyone can point me in the right direction. I want to size the neutral cable on a 3600kW three-phase generator. Preliminary calculations from a supplier have indicated that each phase circuit would require 4x1000mm2 cables and the neutral would be 1x800mm2 cable. I would like to know the formula required to arrive at this conclusion. As background, the generator operates at 725V, with the neutral solidly earthed at the star point. Any help would be appreciated! Thanks.
3.6MW on 3 phase is 1.2MW phase, so each line needs to be rated for 1.2M/750 or about 1600A.
If you really did mean a 690/400 installation then 1.2M/400 means line current of 300A
If divided over 4 cores each carrying 400A each then either the run is long and you are voltage drop limited, or something closer to 300mm2 cores would be OK for the 690 to ground case, or perhaps 400-500mm2 if we mean 440 to ground. You do not mention ducting, grouping or or spacings so there is scope for some variation.
3.6MW on 3 phase is 1.2MW phase, so each line needs to be rated for 1.2M/750 or about 1600A.
If you really did mean a 690/400 installation then 1.2M/400 means line current of 300A
If divided over 4 cores each carrying 400A each then either the run is long and you are voltage drop limited, or something closer to 300mm2 cores would be OK for the 690 to ground case, or perhaps 400-500mm2 if we mean 440 to ground. You do not mention ducting, grouping or or spacings so there is scope for some variation.
