Closed-circuit rotor cooling arrangement and electric machine having same

A rotor cooling arrangement for an electric machine used in a drive train of a work vehicle, the electric machine having a housing containing a stator disposed within the housing in a fixed position about a rotation axis, the rotor cooling arrangement including:

• a rotor disposed within the housing about the rotation axis, the rotor having a series of rotor discs with pockets in which magnets are disposed, the rotor discs being separated from each other along the rotation axis by a dielectric;
• and
• a rotor shaft extending along the rotation axis and coupled to the rotor to corotate relative to the stator about the rotation axis, the rotor shaft having a multi-sided cross section with multiple facets at which are defined, in part, a cooling circuit through which flows a coolant for cooling the rotor, the cooling circuit includes a feed passage internal to the rotor shaft communicating with a cooling passage, in the form of an open groove in an outer surface of the rotor shaft, communicating with an outlet opening spaced along the rotation axis from the rotor;
• wherein the rotor closes off the open groove such that the cooling circuit is a closed loop circuit in which the coolant circulates through the rotor shaft from the feed passage to the cooling passage to the outlet opening.