1. What is Cable Voltage Drop?

Voltage drop refers to the reduction in voltage in an electrical circuit between the source and load. In cable systems, it occurs due to the resistance of the conductors. The UK standards typically recommend keeping voltage drop below 3% for lighting circuits and 5% for other circuits.

2. How Does the Calculator Work?

The calculator uses the standard voltage drop formula:

Where:

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

Explanation: The formula calculates the voltage drop based on the cable's resistance per unit length, the current flowing through it, and the total length of the run.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical equipment receives adequate voltage to operate correctly. Excessive voltage drop can lead to equipment malfunction, reduced efficiency, and potential safety hazards.

4. Using the Calculator

Tips: Enter the cable's mV/A/m value (available from manufacturer specifications), 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 a typical mV/A/m value for cables?
A: For example, 1.5mm² twin and earth cable is about 29 mV/A/m, while 2.5mm² is about 18 mV/A/m. Always check manufacturer specifications.

Q2: Why divide by 1000 in the formula?
A: The division converts millivolts (mV) to volts (V) for the final result.

Q3: What's the maximum acceptable voltage drop?
A: In the UK, BS 7671 recommends max 3% drop for lighting and 5% for other circuits from the supply origin to the load.

Q4: Does voltage drop affect power consumption?
A: Yes, voltage drop represents power lost as heat in the cables, which affects overall system efficiency.

Q5: How can I reduce voltage drop?
A: Use larger cable size, reduce cable length, or decrease the load current where possible.