Abstract: A cooling case for an electrical device, the case comprising:a thermally conductive inner ferrule for surrounding the electrical device;an outer enclosure adjacent to the outside surface of the inner ferrule and including a feed inlet and an exhaust outlet for a cooling fluid, the enclosure being in the form of a plurality of undulations; anda passage for the cooling fluid extending from the inlet to the outlet; the plurality of undulations cooperating with the inner ferrule to define said passage, the cooling fluid being suitable for coming into thermal contact with the inner ferrule.The undulations are formed in such a manner that the passage includes two substantially parallel sections that communicate with each other at one end such that the fluid inlet and the fluid outlet are located substantially towards the same free opposite ends of said sections.