aNerdyEngineer
Member
- Location
- Menomonee Falls, WI, USA
I have a multiple VFDs set up powered from a common DC bus. Each has DC branch fuse protection (though not required in UL508A 31.3.2 exception#2). How would you size these conductors that connect the DC bus to the VFD? 430.122 mentions 125% of drive input (assuming AC input). The drives have rated drive input currents in AC, but not input into the DC bus. Would you calculate off 430.250, or nameplate and convert to DC, or off the DC fuse size?