When to use: Use this when sizing the output power conductors and conduit between a variable-frequency drive and its motor. Per NEC 430.122, VFD output conductors must be rated at 125% of the drive's rated input current. The required ampacity is further adjusted for high carrier (switching) frequency, long cable runs, and elevated ambient temperature, then matched to the smallest THHN conductor that meets it. Always use VFD-rated symmetrical shielded cable for EMC.