1. What is a Cable Voltage Drop Calculator (UK)?

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

Purpose: It helps electricians and engineers ensure proper voltage levels at the load end of electrical circuits.

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 equipment receives sufficient voltage to operate correctly and meets UK wiring regulations (BS 7671).

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What's the maximum allowed voltage drop in the UK?
A: For lighting circuits, 3% of supply voltage; for other uses, 5% (BS 7671 regulations).

Q2: What resistivity value should I use for copper?
A: 1.68×10⁻⁸ ohm-m for copper at 20°C (1.72×10⁻⁸ at 25°C).

Q3: Does this calculator work for three-phase systems?
A: No, this is for single-phase. Three-phase uses a different formula (replace 2 with √3).

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

Q5: What affects voltage drop most significantly?
A: Cable length and current have the greatest impact on voltage drop.