Cooling apparatus for cooling a multi-pole rotor

There is provided a cooling device for cooling a about a rotation axis 2 rotatably mounted rotor 1 of an electrical machine, the rotor 1 is carried by a central rotor shaft 3 and comprises a cavity 5 in the inside of the rotor shaft 3 for receiving refrigerant. 6 The cooling device has at least one radially extending from the cavity 5 to the outside first refrigerant line 7a and a through the first refrigerant line 7a with the cavity 5 fluidly connected annular first manifold 11a. Further, a rotor of an electrical machine with such a cooling device as well as such an electrical machine can be given.