mikedionne
Member
- Location
- Carrollton, Texas
In NEC Article 430 Section X - Adjustable Speed Drives. They provide methods to size the conductors and the disconnects. My question here is what is the proper way to size the main feeder branch circuit protection to a system with a combination of loads that included VFD's & Full Voltage Motor Starters? What I have been doing is taking the largest overcurrent device and then adding all the other loads to it. I use the nameplate rating of the VFD (if it is the largest device I do not use the input fuse or circuit breaker) or the the largest Branch Circuit / Short Circuit device if it is a Full Voltage Starter and then add all the other loads to it. How has everyone else been doint it?