Hello,
We have a 3kw offline battery charger which we bought and they keep stopping working.
We therefore took it apart, and we noticed a 3kW LLC converter using a transformer of Epcos PQ35/35 dimensions and shape. (yes, it was really THAT small!)
Anyway, this transformer is thermally coupled to a 5mm thick aluminium plate heatsink as in the attached diagram.
Surely having a metal plate close to the open side of a high frequency transformer (the PQ35/35 core is not shielded) is going to result in too much eddy current heating in the aluminium heatsink?