Arrangement and method for cooling an electrical machine

In the arrangement according to the invention for cooling an electrical machine, the electrical machine (1) comprises an external rotor (2) rotating around its rotation axis and a stator (5) comprising sheet packs (4), located inside the rotor at the end of an air gap (3). In the arrangement, the first part of the coolant flow (6a) is conductable from both ends of the stator (5) through axial cooling channels (7a-b) into the stator sheet pack (4). The second part of the coolant flow (6b) is conductable from both ends of the stator (5) into the air gap (3) and from the air gap (3) through at least one radial cooling channel (8) into the stator sheet pack (4). Both parts of the coolant flow (6a-b) are conductable into at least one heat exchanger (9) within the stator sheet pack. In the heat exchanger (9), the heat-exchanging surface (10) forms a closed channel for the external coolant flow, and, on the other side of the heat-exchanging surface (10), the first (6a) and the second (6b) parts of the coolant flow are allowed to flow freely. Inside the heat exchanger (9) in the radial direction (R), there is at least one fan (11) for the purpose of sending the first and second parts of the coolant flow (6a-b) to the stator (5) ends.