A traction box intended to be arranged on the roof of a railway vehicle, said box including: at least one upper cover panel, the or each upper cover panel being movable between an open position and a closed position; and an electric power module including: - an electric current conversion device and - a device for cooling the conversion device; said conversion device including a plurality of conversion units, each conversion unit comprising: a support, a plurality of semiconductor elements and an electronic board for controlling said semiconductor elements, the semiconductor elements and the electronic board being fastened to the support; said cooling device comprising a plurality of first heat exchangers such that, in an assembled position of a first heat exchanger with a conversion unit, the plurality of semiconductor elements is in thermal contact with said first heat exchanger so as to yield heat to said first heat exchanger; the module comprising means for removably assembling the support of each conversion unit with the corresponding first exchanger, said support being apt to be dissociated from said first exchanger and from the rest of the electric power module; the traction box being characterized in that: - the or each upper panel is intended, in the closed position, to be inclined at an angle comprised between 20° and 60° with respect to the horizontal; and - the traction box comprises an internal structure including at least one inclined plane, arranged under at least one upper panel and substantially parallel to said upper panel in the closed position; a space located between said upper panel and said inclined plane forming an internal compartment of the traction box each conversion unit being located in said inner compartment, facing said or one of said upper cover panels. - an electric current conversion device and - a device for cooling the conversion device; said conversion device including a plurality of conversion units, each conversion unit comprising: a support, a plurality of semiconductor elements and an electronic board for controlling said semiconductor elements, the semiconductor elements and the electronic board being fastened to the support; said cooling device comprising a plurality of first heat exchangers such that, in an assembled position of a first heat exchanger with a conversion unit, the plurality of semiconductor elements is in thermal contact with said first heat exchanger so as to yield heat to said first heat exchanger; the module comprising means for removably assembling the support of each conversion unit with the corresponding first exchanger, said support being apt to be dissociated from said first exchanger and from the rest of the electric power module; the traction box being characterized in that: - the or each upper panel is intended, in the closed position, to be inclined at an angle comprised between 20° and 60° with respect to the horizontal; and - the traction box comprises an internal structure including at least one inclined plane, arranged under at least one upper panel and substantially parallel to said upper panel in the closed position; a space located between said upper panel and said inclined plane forming an internal compartment of the traction box - the or each upper panel is intended, in the closed position, to be inclined at an angle comprised between 20° and 60° with respect to the horizontal; and - the traction box comprises an internal structure including at least one inclined plane, arranged under at least one upper panel and substantially parallel to said upper panel in the closed position; a space located between said upper panel and said inclined plane forming an internal compartment of the traction box each conversion unit being located in said inner compartment, facing said or one of said upper cover panels.