Cable capacity reduction due to harmonics
Cable capacity reduction due to harmonics
(OP)
Hello,
We have a cable installation (separate conductors) feeding a VFD - 5.5 MVA. Converter is "6-pulse" type.
The feeding cables will run 98% full load (24-7), and we are not sure if the cable capacity should be upgraded due to the harmonics. Right now we have not the exact numbers for THD and frequency content, but can anyone give us general design hints and common practices. Also litterature recommendations are highly appreciated.
Best Regards
Petersen
We have a cable installation (separate conductors) feeding a VFD - 5.5 MVA. Converter is "6-pulse" type.
The feeding cables will run 98% full load (24-7), and we are not sure if the cable capacity should be upgraded due to the harmonics. Right now we have not the exact numbers for THD and frequency content, but can anyone give us general design hints and common practices. Also litterature recommendations are highly appreciated.
Best Regards
Petersen






RE: Cable capacity reduction due to harmonics
If you can get hold of a text by G. Anders on Cable Rating, I think you will find more detailed methods that account for some of the assumptions mentioned above.
RE: Cable capacity reduction due to harmonics
Is that 98% of the actual capacity? I hope not.
RE: Cable capacity reduction due to harmonics
And yes, the current in the cables will be 98% of the rated cable capacity (if we do not change the cables).
wereagle "hope not" why?
RE: Cable capacity reduction due to harmonics
You post "The feeding cables will run 98% full load (24-7)"
is the reason I asked the question. I may not understand you situation correctly but the NEC requires cable to have an ampacity of 125% of the continuous load which makes the cable 80% loaded.