Percentage voltage drop, on a three-phase line. ΔU = √3·ρ·L·I·cosφ / A Calculated using (coefficient 2 in single phase) and divided by voltage to convert to a percentage. General rule: ≤ %3 for lighting circuits, ≤ %5 for other applications.
3F: ΔU = √3·ρ·L·I·cosφ / A 1F: ΔU = 2·ρ·L·I·cosφ / A
Example calculation: 3-phase 400 V line, 63 A, 45 m, 16 mm² copper, cosφ 0.9 → ΔU ≈ 4.9 V, i.e., below the limits of %1.23 → %3 and %5 (suitable).
Voltage Drop & Cable Cross-Section
Calculate the approximate percentage voltage drop of a line and compare it to the %3–5 reference limits.
Voltage drop
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Percentage
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Notes: 3F: ΔU=√3·ρ·L·I·cosφ/A · 1F: ΔU=2·ρ·L·I·cosφ/A. This is an ohmic approach; cable reactance and temperature correction are neglected. Reference limit: lighting ≤ %3, other uses ≤ %5 (TS EN 60364 / relevant regulation). The full method is applied for precise calculation.
How is it calculated?
- Select the system (1F/3F) and voltage.
- Enter the load current (A), line length (m), and cross-section (mm²).
- Select the conductive material and cosφ, then click Calculate.
Frequently Asked Questions
What percentage voltage drop should there be?
General reference: maximum %3 for lighting circuits, maximum %5 for other circuits (TS EN 60364 / relevant regulation).
How can voltage drop be reduced?
This can be reduced by increasing the cable cross-section, shortening the line, or moving the feed point closer to the center of the load.
Does this calculation include reactance?
This tool uses the ohmic (resistive) approach; cable reactance and temperature correction are excluded. The full method should be applied to long/high-current lines.
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