Axial flux electric motor with rotor cooling

A method of cooling an axial flux electric motor, the method comprising:

• obtaining, via an electronic controller, data indicative of an operating point of the axial flux electric motor, wherein the axial flux electric motor includes:
• a rotationally-fixed stator defining a rotational axis and having a plurality of conductive stator magnetic poles arranged radially about the rotational axis;
• a rotor spaced axially from one side from the stator and rotatably mounted coaxially with the rotational axis, defined by an inside diameter and an outside diameter, and having a rotor first exterior surface facing the stator and a rotor second exterior surface arranged opposite the rotor first exterior surface, wherein:
• the rotor includes a ferromagnetic rotor core defining the rotor second exterior surface and a plurality of alternating south and north pole permanent magnets (PMs) arranged on the ferromagnetic rotor core symmetrically around the rotational axis and facing the stator;
• the ferromagnetic rotor core includes a plurality of core saliencies extending to the rotor first exterior surface;
• each pair of alternating south and north pole PMs of the rotor includes one of the core saliencies arranged therebetween;
• at least one of the plurality of channels extends on the rotor first exterior surface between one of the PMs and one of the saliencies;
• a plurality of channels extending radially outwardly across the rotor and configured to direct a coolant, via centrifugal force, from the inside diameter toward the outside diameter as the rotor rotates about the rotational axis;
• and
• the obtained data includes a phase current, rotational speed, temperature, and a flow rate of the coolant in the axial flux electric motor;
• identifying, via the electronic controller, the operating point on an operation map of the axial flux electric motor;
• comparing, via the electronic controller, the obtained temperature to a predicted temperature corresponding to the operating point;
• and
• commanding, via the electronic controller, a predetermined coolant flow rate through the plurality of channels when the obtained temperature is greater than the predicted temperature to cool the axial flux electric motor.

A cooled axial flux electric motor comprising:

• a rotationally-fixed stator defining a rotational axis and having a plurality of conductive stator magnetic poles arranged radially about the rotational axis;
• a rotor spaced axially from one side of the stator and rotatably mounted coaxially with the rotational axis, defined by an inside diameter and an outside diameter, and having a rotor first exterior surface facing the stator and a rotor second exterior surface arranged opposite the rotor first exterior surface, wherein the rotor includes:
• a ferromagnetic rotor core defining the rotor second exterior surface and a plurality of alternating south and north pole permanent magnets (PMs) arranged on the ferromagnetic rotor core symmetrically around the rotational axis and facing the stator;
• and
• a plurality of channels extending radially outwardly across the rotor and configured to direct a coolant, via centrifugal force, from the inside diameter toward the outside diameter as the rotor rotates about the rotational axis;
• and
• wherein:
• the ferromagnetic rotor core includes a plurality of core saliencies extending to the rotor first exterior surface;
• each pair of alternating south and north pole PMs of the rotor includes one of the core saliencies arranged therebetween;
• and
• at least one of the plurality of channels extends on the rotor first exterior surface between one of the PMs and one of the saliencies;
• a rotor shaft fixed to the rotor and mounted rotationally inside the stator coaxially with the rotational axis, wherein the rotor shaft defines a fluid passage configured to supply the coolant to the plurality of channels;
• and
• a housing defining a fluid sump configured to collect the coolant after the coolant has passed through the plurality of channels and return the coolant to the fluid sump via gravity.