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Enter the design current, cable length, cross-section, power factor and voltage to get the voltage drop in volts and percent, checked against the common IEC 60364-5-52 limits. Defaults are the benchmark for a 230/400 V three-phase circuit with 150 m of 35 mm² copper.
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Inputs: I_B = 100 A, L = 150 m, S = 35 mm², copper ρ₁ = 0.0225 Ω·mm²/m, λ = 0.08 mΩ/m, cos φ = 0.85, U₀ = 230 V, three-phase
| Relative voltage drop Δu | 3.839 % |
|---|---|
| Voltage drop u (IEC Annex G) | 8.829 V |
| Circuit voltage drop ΔU (line-to-line for three-phase) | 15.29 V |
| Conductor resistance R | 0.09643 Ω |
The example matches industry benchmark GC-IND-EL-VD-001 in our repository (expected values derived independently with 50-digit decimals and checked by automated tests).
IEC 60364-5-52 recommends 3 % for lighting and 5 % for other uses when supplied directly from a public LV network, and 6 % / 8 % from a private supply. Local rules may differ; check your national code.
In a single-phase circuit the current flows through both the line and neutral conductors, so b = 2; in a balanced three-phase circuit the neutral carries no current and b = 1. Percentages are relative to the phase voltage U₀.
IEC Annex G uses the resistivity at normal operating temperature, about 1.25 times the 20 °C value: 0.0225 for copper and 0.036 for aluminium.
Without manufacturer data IEC uses 0.08 mΩ/m. Large single-core cables laid apart have higher reactance; use the manufacturer's value.
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