Donaldson R F Voltage Drop Calculator
Estimate the voltage drop over a cable run, from its length, cross-sectional area, current and conductor material.
How it is worked out
Cable resistance R = ρ × L ÷ A, where ρ is the conductor's resistivity, L is the length run and A is the cross-sectional area. For a single-phase circuit the current flows out and back, so the voltage drop uses twice the one-way length: Vdrop = 2 × I × R. For a three-phase circuit, Vdrop = √3 × I × R (using the one-way length).
Source: standard conductor resistivity values at normal operating temperature — copper 0.0175 Ω·mm²/m, aluminium 0.0282 Ω·mm²/m — e.g. Engineering ToolBox: Resistivity of conductors.
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