Voltage Drop Calculation Method

Three-Phase % Voltage Drop = Load in Amps * Effective Z * (Wire Length / 1,000) * 100 / Line-to-Neutral Voltage

Single-Phase % Voltage Drop = Load in Amps * Effective Z * (Wire Length / 1,000) * 100 * 2 / Voltage

Load in Amps 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.

Effective Z = R * Power Factor + X sin(arccos(Power Factor)) (See NEC Table 9 Note 2)

R = Resistance set in the Wire Sizing command.

X = Reactance set in the Wire Sizing command.

Power Factor = 0.85

Line-to-Neutral Voltage 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 by the user.

The transformer impedance values are for dry-type indoor transformers. These values can be modified by the user.