Voltage Drop Calculation Method
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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 / Line-to-Neutral 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 (acos(Power Factor)) (NEC Table 9 Note 2)
R = Resistance set in the command.
X = Reactance set in the command.
Power Factor = 0.85
Line-to-Neutral Voltage is used based upon NEC Table 9 Note 2: "Multiplying current by effective impedance gives a good approximation for line-to-neutral voltage drop."
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.
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