Voltage Drop With Reactance
Single- or three-phase voltage drop using NEC Chapter 9 Table 9 R and X per 1000 ft and the load power factor, with the 3% / 5% advisory band.
Formula and source
Vd = k * I * (R*cos(theta) + X*sin(theta)) * L / 1000, with k = 2 single-phase or sqrt(3) three-phase and theta = arccos(PF). R and X per 1000 ft are selected by conductor size and conduit material.
NEC 2023 (NFPA 70). Chapter 9 Table 9 (R and X per 1000 ft); 210.19(A) Note 4 (3% branch) and 215.2(A)(1) Note 2 (5% total) advisory bands.
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