I encountered a passive harmonic filter, PHF with highly non linear loads, i.e. variable frequency drive, VFD (most of the time running 50Hz) serving an induction motor.
I believe that it is a commonly used resonant shunt filter to eliminate the 5th harmonic.
The enclosure housing the PHF has a ventilation fan, but still always (the reason why I am writing here) very HOT! Up to the extent that the contactors, wires have melted/discolorated/burnt mark etc
I suspect of the over saturation of the 3 phase transformer (V_phase2phase=415V), I believe acts as an isolation transformer-cum-line reactor. The capacitors are still in good condition (not bulging of the caps), but the winding insulation of the transformer is discoloured.
Any help to do further diagnostic is welcomed. I will conduct a harmonic assessment with a Fluke power analyser next week.