Electrical machine, in particular AC generator, having a stator (16) and a rotor (20), wherein the rotor (20) has a conductor arrangement for exciting an electromagnetic field, having a device for transmitting electrical energy to the conductor arrangement, wherein the device for transmitting electrical energy comprises at least one sliding contact and at least one mating contact (66) which is fixed to the rotor, having a fitting sleeve (63) in which a roller bearing (28) for supporting a shaft (27) is preferably arranged, said shaft for the most part encasing the at least one mating contact (66) which is fixed to the rotor, wherein a fan (70) is arranged in the fitting sleeve (63).