Transformer Running Hot Under Normal Load
Transformer case temperature is noticeably higher than usual, sometimes with a faint burning smell, even though load appears within nameplate rating.
Cooling fan/radiator obstruction, overloading beyond actual nameplate due to harmonics, low oil level (oil-filled units), or degraded insulation increasing losses.
Allow the transformer to cool before physical inspection. Follow arc-flash PPE requirements when working near energized bushings.
1) Check actual load current on all three phases against nameplate FLA.\n2) Inspect cooling fins/fans for dust, blockage, or fan failure.\n3) Check oil level and oil dielectric strength if oil-filled.\n4) Measure harmonic content if the load is largely non-linear (VFDs, rectifiers).
Clamp meter, infrared thermometer, oil test kit (if applicable), power quality analyzer
1. Confirm loading is genuinely within nameplate — true RMS current, not just a rough estimate.\n2. Clean or repair any blocked cooling path; replace failed cooling fans.\n3. If oil-filled, test and top up or replace degraded oil.\n4. If harmonics are high, address at the source (drive filters) rather than just the transformer.
Add cooling fin cleaning and thermal imaging to the annual maintenance checklist.
A transformer that's hot but not tripping any protection is often a cooling problem, not an electrical fault — check airflow before assuming an internal winding issue.