Electromechanical machine, comprising at least one part consisting of a winding made of a material that becomes electrically superconductive when its temperature is lower than a critical temperature Tc, a functional part of said electromechanical machine being contained in an internal volume delimited by a wall of a thermally insulating and fluid-tight enclosure, characterized in that the internal volume comprises a tank intended to store cryogenic fluid, in the liquid state when the temperature is lower than the critical temperature Tc, not insulated with respect to the internal volume in terms of thermal conduction, the tank being formed by an internal separator determining, between said internal separator and a more outer separator of the wall, a volume of the tank, and determining, on the side of an inner face, a smaller volume in which the functional part is located and in that the internal volume comprises: - for a temperature range between an initial temperature Tmin, equal to the temperature of a cryogenic fluid and a maximum operating temperature Tmax, at most equal to the critical temperature Tc, - a capacity for storing thermal energy in static form and - a capacity for storing energy by latent heat from vaporization of a quantity of cryogenic fluid filling the tank, the capacity for storing thermal energy in static form plus said capacity for storing energy by latent heat from vaporization of the cryogenic fluid representing at least the quantity of heat Emax introduced into said internal volume, when the electromechanical machine is used for a duration and in operating conditions corresponding to those of an uninterrupted mission the most detrimental with respect to said quantity of heat out of a set of missions in which said electromechanical machine is likely to be used. characterized in that the internal volume comprises a tank intended to store cryogenic fluid, in the liquid state when the temperature is lower than the critical temperature Tc, not insulated with respect to the internal volume in terms of thermal conduction, the tank being formed by an internal separator determining, between said internal separator and a more outer separator of the wall, a volume of the tank, and determining, on the side of an inner face, a smaller volume in which the functional part is located and in that the internal volume comprises: - for a temperature range between an initial temperature Tmin, equal to the temperature of a cryogenic fluid and a maximum operating temperature Tmax, at most equal to the critical temperature Tc, - a capacity for storing thermal energy in static form and - a capacity for storing energy by latent heat from vaporization of a quantity of cryogenic fluid filling the tank, - for a temperature range between an initial temperature Tmin, equal to the temperature of a cryogenic fluid and a maximum operating temperature Tmax, at most equal to the critical temperature Tc, - a capacity for storing thermal energy in static form and - a capacity for storing energy by latent heat from vaporization of a quantity of cryogenic fluid filling the tank, the capacity for storing thermal energy in static form plus said capacity for storing energy by latent heat from vaporization of the cryogenic fluid representing at least the quantity of heat Emax introduced into said internal volume, when the electromechanical machine is used for a duration and in operating conditions corresponding to those of an uninterrupted mission the most detrimental with respect to said quantity of heat out of a set of missions in which said electromechanical machine is likely to be used.