Cables and wires

Cable voltage drop

Calculate the voltage drop of a single- or three-phase circuit and find the smallest cross-section within the limit.

CalculatorVisualisationMethod: ΔU% = √3·100·I·R·cos φ / U (Warsaw University of Technology, eSezam 4.3–4.8)
01 / CIRCUIT

Circuit and cable

Enter the load, line length and cable. The result updates as you type.

Supply
Conductor material
The designer sets the limit (for example from the connection conditions or HD 60364-5-52).
VOLTAGE DROP
1.96 %
Within 3.0%
Load current35.3 ADrop in volts7.9 VVoltage at the end392.1 VSmallest section within the limit10 mm²
VOLTAGE DROP BY CROSS-SECTION
13.1
1.5
7.9
2.5
4.9
4.0
3.3
6.0
2.0
10
1.2
16
0.8
25
0.6
35
0.4
50
0.3
70
0.2
95
0.2
120
ΔU [%] by cross-section [mm²] · other inputs unchanged · limit 3.0%
i

The model ignores cable reactance, which understates the result above about 50 mm² Cu (70 mm² Al). Conductivity is taken at about 20°C; at operating temperature the resistance is higher. Voltage drop is one sizing criterion: also check current-carrying capacity and shock protection. The result is for preliminary calculations and must be checked in the design and by measurement. It does not confirm that the installation complies with standards.

Method and assumptions

1f: ΔU% = 200 / U_f · I · R · cos φ
3f: ΔU% = √3 · 100 / U_N · I · R · cos φ
R = l / (γ · S)

I: load current from active power and cos φ; l: line length in metres; S: cross-section in mm²; γ: conductivity, 56 m/(Ω·mm²) for copper and 33 for aluminium. Source: Warsaw University of Technology, eSezam, “Voltage drop calculations”, formulas 4.3–4.8.