The end plate can have a central through-opening for guiding through the shaft. The collar can be formed radially outwardly in the circumferential direction, wherein the elevations and the collar axially delimit the second and fourth cooling channel, wherein the cooling channel portions of the cooling channel are delimited by an elevation at each of the two ends, wherein two elevations delimiting a cooling channel portion are distanced from one another by a first arc length in a first radial position between the through-opening and the collar and are distanced from one another by a second arc length, which is greater than the first arc length, in a second radial position delimited by collars. Each cooling channel portion typically extends as far as the through-opening.

A cooling channel portion advantageously has at least one fluid-guiding element between the first radial portion and second radial portion. A fluidically improved distribution of the cooling fluid within the magnet pockets thus can be achieved within the magnet pockets, which makes possible a greater cooling performance of the electric machine. At the same time, an inhibition, in particular a prevention, of the axial movement of the permanent magnet can be achieved by the at least one fluid-guiding element without additional structural elements, which results in a greater mechanical stability of the rotor assembly.

For example, a fluid-guiding element can be provided which is formed by a protuberance of an elevation. The fluid-guiding element, which is also referred to hereinafter as a first fluid-guiding element, consequently provides a bulging that narrows the cooling channel portion. The first fluid-guiding element is used preferably to support a permanent magnet, in particular a radially inner permanent magnet.