Voltage Drop Calculator
Short answer
Voltage drop = k × ρ × length × current ÷ area (k = 2 single-phase, √3 three-phase).
Voltage drop3.79V
Voltage drop0.91%
Vd = k·ρ·L·I / A (k = 2 single-phase, √3 three-phase). Indicative; verify against cable data and standards.
Formula
Vd = k × ρ × L × I ÷ A · %drop = Vd ÷ V × 100
How it works
ρ is the conductor resistivity (≈ 0.0175 Ω·mm²/m copper, ≈ 0.028 aluminium). k is 2 for single-phase and √3 for three-phase. Keep drop within limits (commonly a few percent).
Worked example
Three-phase, 50 m, 40 A, 16 mm² copper: Vd ≈ √3 × 0.0175 × 50 × 40 ÷ 16 ≈ 3.79 V (≈ 0.9% of 415 V).
Frequently asked questions
- What voltage drop is acceptable?
- Design limits are commonly a few percent of nominal voltage; always verify against the applicable standard and cable data.
Related resources
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