I have used this calculation for three phase E drop is it ok ? 2xKxDxI divided by allowable e drop=CM of wirex.866 note for three phase is this ok thanks ED
My Herman book describes this formula use for odd timing of current peaks in 3-phase systems, by multiplying wire length by 0.866. However, without engineering supervision NEC compliance restricts me to the properties listed in NEC Tbl.310-16(-86), & Tbl. 8 & 9, based on 1000 foot lengths.
Iduno if that 3-phase 0.866 factor was built into the 1000.ft figures on table 9, which deals with 3-phase XL, R, & Z values, but I'm not allowed to modify the conductor properties or lengths listed there. Maybe engineering supervision that uses NEC Appendix C formulas to develop specs. for prints, can also use other formulas?
One effort to develop a Target Voltage template based on these NEC tables was last discussed with this Unusual Power Distribution Setup.
Looking closer, Tbl.9 shows "Ohms to Neutral per 1000 Feet". Impedance doesn't change with current, but voltage does. VD calcs need this adjustment, and using 0.866 to adjust current is ok, since Tbl. 9 values of (Z) and (Lenth) are not modified by doing so.
