Marco, The formulas I learned in school are:
Single-Phase Vd = (2 * d * k * I) / cm where: d = distance; the constant k = 12.9 Ohms for Cu & 21.2 Ohms for AL; I = current; cm = circular mils 3-Phase Vd = (1.73 * d * k * I) / cm My note are failing me, but I believe d is actually the one-way distance. This is multiplied by 2, in the single-phase calculation, to account for the round trip distance. In the 3-phase calculation 1.73 is used instead. Table 8 in the NEC has the conductor properties. This is where I always look up circular mils. In the past I¹ve run these calculations against my ElectriCalc & had things check out. > > I feel kinda foolish in asking this.....but when calculating voltage drop in a > conductor over distance, do I use the one-way or round-trip distance? thanks, > marco Marco Mangelsdorf, Ph.D., President > Electrical Contractor License C-26351 > 69 Railroad Avenue, Suite A-7 > Hilo, Hawaii 96720 USA > (808) 969-3281, fax 934-7462 www.provisiontechnologies.com > <http://www.provisiontechnologies.com/> > > > > > David Brearley, Technical Editor > SolarPro magazine > NABCEP Certified PV Installer > [EMAIL PROTECTED] > Direct: 541.261.6545 > Fax: 541.512.0343 > > Visit our Web site at solarprofessional.com
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