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Voltage Drop

Receiving voltage for AC or DC circuits.

Calculation inputs

Illustrative example values — replace them before any engineering decision.

Engineering results

Voltage drop5 V
Voltage drop1.25 %
Receiving-end voltage395 V

Method and traceability

R=ρ₂₀·[1+α·(T−20)]/S. AC drop includes entered reactance and cosφ; length is one way. DC and single phase include the return path; balanced three phase uses √3.

Visible assumptions: copper ρ₂₀ 0.0175 and aluminium 0.0282 Ω·mm²/m; copper α 0.00393 and aluminium 0.00403/°C. Reactance, density, factors and thresholds remain editable.

Screening lists — sections: 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500, 630 mm²; breakers: 2, 4, 6, 10, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600 A; transformers: 25, 50, 100, 160, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150 kVA.

Final design must verify applicable IEC 60364 requirements, actual thermal conditions, short circuit, shock protection, selectivity, starting, harmonics and local rules.

IEC 60364-5-52 ↗Guide — voltage drop ↗

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Engineering reference

Voltage Drop Calculator

Calculate conductor voltage loss, percentage drop and receiving voltage for AC or DC circuits.

Calculation method

Resistance is corrected from 20 °C to the entered conductor temperature. AC calculations combine resistance, reactance and power factor; DC uses the resistive two-conductor path.

Formulas used

  • Three phase: ΔV = √3 × I × (R cosφ + X sinφ) × L
  • Single phase: ΔV = 2 × I × (R cosφ + X sinφ) × L
  • Drop percentage: 100 × ΔV / V

Worked example

Example: a calculated 12 V drop on a 400 V circuit represents 3%; the receiving voltage is about 388 V.

How to interpret the result

Compare the percentage with the project limit and the equipment’s required terminal voltage, not with an assumed universal limit.

Common mistakes

  • Using total route length instead of one-way length.
  • Ignoring conductor operating temperature.
  • Using conductor size without confirming its actual material.

Scope and limitations

  • The calculation does not replace harmonic, starting-transient or detailed network studies.

Frequently asked questions

What does a 3% voltage drop mean?

The load receives 97% of the entered nominal sending voltage under the modeled current and conditions.

Why is cable temperature included?

Conductor resistance rises with temperature, increasing voltage drop for the same current.

Is reactance relevant in DC?

No. This engine uses the resistive two-way path for DC.