1. What is Volt Drop in SWA Cables?

Volt drop in SWA (Steel Wire Armored) cables refers to the reduction in voltage that occurs as current flows through the cable due to its resistance. It's important to calculate to ensure adequate voltage reaches the load.

2. How Does the Calculator Work?

The calculator uses the volt drop equation:

Where:

• \( mV/A/m \) — Millivolts per amp per meter (cable characteristic)
• \( I \) — Current in amps
• \( L \) — Length of cable in meters

Explanation: The equation calculates the voltage drop based on the cable's specific resistance (mV/A/m), the current flowing through it, and the length of the cable run.

3. Importance of Volt Drop Calculation

Details: Calculating volt drop is crucial for ensuring electrical equipment receives sufficient voltage to operate correctly and for compliance with electrical regulations.

4. Using the Calculator

Tips: Enter the cable's mV/A/m value (from manufacturer data), the expected current in amps, and the cable length in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is an acceptable volt drop?
A: Generally, volt drop should not exceed 3% for lighting circuits or 5% for other circuits from the supply to the load.

Q2: Where can I find mV/A/m values?
A: These values are provided in cable manufacturer datasheets or electrical reference books like the IET Wiring Regulations.

Q3: Does temperature affect volt drop?
A: Yes, cable resistance increases with temperature, which would increase volt drop slightly in warm conditions.

Q4: How does cable size affect volt drop?
A: Larger cables have lower mV/A/m values, resulting in less volt drop for the same current and length.

Q5: Should I include both live conductors in the calculation?
A: For single-phase AC, yes - the length should be the total out and back distance (2 × one-way length).