Why Cables get hot even below Rated Current?
Have you ever observed your wires heating up even if the current is well inside the rated limit.
This is a concealed hazard that diminishes efficiency, increases energy loss & can even lead to insulation failure.
Ambient Temperature and Derating
Cables are rated at 30°C ambient, however in industries or cable tunnels, temperatures frequently exceed 45-50°C.
Bigger resistance leads to bigger losses and more heat.
Cable Grouping
When several cables are put side by side, heat dissipation decreases.
So, while if each carries “rated current,” they trap heat together, resulting in concentrated hot areas.
Poor Ventilation (or) Conduit Design
Cables are frequently routed through narrow ducts in steel factories or MCC panels.
No airflow means no cooling, which leads to rising temperatures and insulation breakdown.
Skin Effect (AC Systems)
At greater currents, current tends to flow along the outside surface of conductors.
As the effective area decreases, the resistance increases, leading to further heating.
Use derating factors for ambient, grouping & laying method when choosing cable size.
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