At a school, a single continuous-duty, low-speed, three-phase motor has a nameplate full-load current of 50 amperes. For this motor, 2026 NEC 430.6 requires use of the nameplate current rather than a table value. It is not part of an adjustable-speed drive system, and the general 125% motor-conductor requirement of 430.22 applies without exception. Its copper THWN-2 branch-circuit conductors are in a raceway with no more than three current-carrying conductors, a 30°C ambient temperature and equipment terminals listed for 75°C conductors. With no other condition requiring a larger size, what minimum conductor size is required?

Where to look it up

https://www.elightinformation.com/post/motor-and-welding-machine-calculation-steps-2026-nec

Why A is correct

50 A × 125% = 62.5 A. In the 75°C copper column of Table 310.16, 6 AWG is rated 65 A and 8 AWG only 50 A. Therefore 6 AWG, A, is the minimum; the smaller choices fail. Use the specified nameplate-current case, not an invented table lookup. This selects the branch conductors, not the overload or short-circuit protective device. Sources: E Light Electric, Motor and Welding Machine Calculation Steps 2026 NEC, current-basis rule and Step 1: https://www.elightinformation.com/post/motor-and-welding-machine-calculation-steps-2026-nec ; Mike Holt Enterprises, Understanding the 2026 NEC Volume 1, first printing January 2026, page 379, Table 310.16 and notes: https://www.mikeholt.com/instructor2/img/product/pdf/1769018196.pdf