2 etc are provided in all the cooling ducts in the center of the gas outlet 4 provided on both sides of the separating wall 16 i located in a radial plane are two first radial ducts 17 1 which lead through the recesses in the winding conductors 2 3 8 9 and 10 to the cooling duct 6 1 in the lowest winding conductor 1 these radial ducts are closed against the rest of the cooling ducts 6 2 6 3 by second separating walls 18 2 18 3 the second separating walls 18 2 18 3 in turn form the boundary for two second radial cooling ducts 19 2 which are in free connection with the cooling ducts 6 2 in the second winding conductor 2 the second radial cooling ducts 18 2 are closed by third separating walls 20 3 20 8 towards the ends of the rotor the third separating walls 20 3 20 8 form the boundary for two third radial ducts 21 3 which are connected to cooling ducts 6 3 in the third winding conductor 3 towards the ends of the rotor the third radial cooling ducts 21 3 are closed by fourth separating walls 22 8 22 9 22 10 this is continued in an analogous manner through fourth radial cooling ducts 23 8 which are bounded by the fourth separating walls 22 8 22 9 22 10 and fifth separating walls.