Conductor Cross-Section
Cable cross-section is the measure in mm² of the current-carrying copper area of the conductor, and it is sold in steps such as 0.75, 1.5, 2.5, 4, 6, 10 and 16 mm². The cross-section is the common input to two separate calculations: current carrying capacity and voltage drop. The larger of the two results is the one that applies.
The cross-section is the area of the copper inside, not the outer diameter of the sheath; a 4 mm² cable can look thinner than a 2.5 mm² cable with a thick sheath. When choosing, ask two questions separately.
- The heating question: can this cross-section carry this current continuously without damaging the insulation? For copper, figures of around 18 A for 1.5 mm², 26 A for 2.5 mm² and 44 A for 6 mm² are typically used; the installation method, bundling and ambient temperature pull these numbers down.
- The distance question: how many volts are left at the load end? On long runs at a low voltage such as 12 V this is usually the deciding factor.
Because most AXI remote controls and drivers are supplied with 12 V or 24 V DC, looking only at the ampacity table when choosing a cross-section is a frequent mistake. If you take a driver drawing 20 A over 5 m with 2.5 mm², the cable will not overheat but you will lose about 1.4 V at the device input; with 10 mm² on the same run this loss falls to 0.35 V.
The context in which this term is used: Installation, redundancy and field continuity