1. What is a Cable Voltage Drop Calculator?

Definition: This calculator estimates the voltage drop in electrical cables based on resistivity, length, current, and cross-sectional area.

Purpose: It helps electricians and engineers ensure proper voltage levels at load points by accounting for cable resistance.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( VD \) — Voltage drop (volts)
• \( \rho \) — Resistivity of conductor material (ohm-m)
• \( L \) — Length of cable (meters)
• \( I \) — Current flowing through cable (amps)
• \( A \) — Cross-sectional area of conductor (m²)

Explanation: The factor of 2 accounts for the return path in single-phase systems. The formula calculates the voltage lost due to cable resistance.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical devices receive adequate voltage and helps prevent energy waste and overheating.

4. Using the Calculator

Tips: Enter the conductor resistivity (default 1.68×10⁻⁸ ohm-m for copper), cable length in meters, current in amps, and conductor area in m². All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the maximum acceptable voltage drop?
A: In the UK, BS 7671 recommends ≤ 3% for lighting and ≤ 5% for other circuits at full load.

Q2: What resistivity value should I use for copper?
A: 1.68×10⁻⁸ ohm-m for copper at 20°C. For aluminum, use 2.82×10⁻⁸ ohm-m.

Q3: Why is the length multiplied by 2?
A: This accounts for both the live and neutral conductors in single-phase AC circuits.

Q4: How do I convert mm² to m² for cable area?
A: Divide mm² by 1,000,000 (e.g., 2.5mm² = 2.5×10⁻⁶ m²).

Q5: Does this calculator work for DC systems?
A: Yes, but remove the factor of 2 for DC systems (VD = ρ × L × I / A).