MCCB in high frequencies (400hz) application
LS Electric MCCBs are suitable for use at 400hz.
Due to higher frequency, the breakers are required to be derated as the increased resistance of the copper sections resulting from the skin effect produced by eddy currents at 400hz.
This is an image from IEC catalog.
UTE/UTS - UL Breakers
Since, IEC Breakers and UL Breakers are identical in structure, the derate will be the same.