1. What is an SWA Cable Voltage Drop Calculator?

Definition: This calculator estimates the voltage drop in Steel Wire Armored (SWA) cables based on resistivity, cable length, current, and cross-sectional area.

Purpose: It helps electrical engineers and electricians ensure proper voltage levels are maintained in cable runs.

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 formula accounts for both the outgoing and return paths (hence the factor of 2) of the current in the cable.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop estimation ensures electrical equipment receives adequate voltage and prevents excessive power loss in cables.

4. Using the Calculator

Tips: Enter the conductor resistivity (default 1.72×10⁻⁸ 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: Why is there a factor of 2 in the formula?
A: The factor accounts for both the outgoing and return paths in single-phase AC or DC circuits.

Q2: What's the typical resistivity for copper?
A: Copper has ρ ≈ 1.72×10⁻⁸ ohm-m at 20°C. For aluminum, use 2.82×10⁻⁸ ohm-m.

Q3: How does temperature affect the calculation?
A: Resistivity increases with temperature. For precise calculations, adjust ρ based on operating temperature.

Q4: What's an acceptable voltage drop?
A: Typically 3% for lighting circuits and 5% for other circuits, but check local regulations.

Q5: How do I convert mm² to m² for cable area?
A: Divide mm² by 1,000,000 (e.g., 10 mm² = 0.00001 m²).