Voltage Drop Calculation Method
Three−Phase%VoltageDrop=Line−to−NeutralVoltageLoadinAmps×EffectiveZ×1,000WireLength×100
Single−Phase%VoltageDrop=VoltageLoadinAmps×EffectiveZ×1,000WireLength×2×100
LoadinAmps is different for feeders and branch circuits. For feeders, it is the calculated load on the panel assuming a balanced load. For branch circuits, it is based upon the connected load.
EffectiveZ=(Resistance×PowerFactor)+(Reactance×sin(arccos(PowerFactor)))
(See NEC Table 9 Note 2)
Resistance and Reactance are set in the Wire Sizing command.
PowerFactor=0.85
Line−to−NeutralVoltage is used for three-phase calculations based upon NEC Table 9 Note 2: "Multiplying current by effective impedance gives a good approximation for line-to-neutral voltage drop."
Voltage is the line-to-neutral voltage for single-pole circuits and line-to-line voltage for two-pole circuits.
The feeder impedance values are based upon NEC Table 9. These values can be modified.
The transformer impedance values are for dry-type indoor transformers. These values can be modified.