Cooling device for an electronic power system

In a cooling device including an electronic power system, said system being connected at an inlet to an electrical supply cable (24) and at an outlet to a conductive cable (17) connected to a system (8) for transmission of current, the device being adapted to be buried in the ground in a concrete box (1) such that the current transmission system will be adapted to transmit a current into an external electrical machine;

• the improvement comprising:
• a sealed metallic receptacle (2) filled with heat transfer liquid;
• a hollow chimney extending vertically from a bottom of the receptacle;
• a sealed compartment (19) located below the bottom (2a) of the receptacle, the sealed compartment opening to the hollow chimney;
• wherein the electronic power system is disposed within the sealed compartment, at least one electronic power component of the electronic power system being directly fixed to a lower surface of the bottom of the receptacle, in a predetermined position so as to give rise in the receptacle (2) to an agitation of the heat transfer liquid by a thermosiphon effect without causing evaporation of the heat transfer liquid.