| Symptom | Infrared Temp | Root Cause | | :--- | :--- | :--- | | Single hot spot at joint | 120°C+ | Loose bolt or missing inhibitor | | Uniformly hot entire length | 95-105°C | Undersized bar or high ambient | | Hot edges, cooler center | 100°C edges | Skin effect (normal but near limit) | | Cyclic heating/cooling | Spikes to 140°C | Loose connection arcing | | Phase-to-phase temperature delta >15°C | N/A | Unbalanced load or proximity effect |
Because aluminium expands and contracts significantly when cycling between cold (ambient) and hot (full load) states, rigid bolting can cause (permanent deformation). When the system cools down, the joint becomes loose, leading to higher resistance and ultimate thermal runaway. indal handbook for aluminium busbar hot