Abstract: A rotor assembly for a dynamoelectric machine is characterized by incorporating three different sets of rotor laminations each of which is provided with punched apertures that respectively form conductor slots arcuately spaced around the periphery of the laminae, a plurality of axial coolant passageways extending through the assembly near its inner diameter, a plurality of arcuately spaced radial ducts at axial intervals along the rotor, and vent passageways connecting the radial ducts to the axial coolant passageways to enable cooling air to be forced through the coolant passageways and the vent apertures into the radial ducts and thence into the air gap of the machine when the rotor is assembled in operating position. The rotor of the invention is particularly characterized by incorporating radial cooling ducts that extend between each adjacent pair of conductor slots from the periphery of the rotor to points substantially below the bottoms of the conductor slots in the rotor laminae.