Development and comparison of various continuous duty cooling concepts for the stator of an SSDR Axial-flux motor

The automotive industry is facing a disruptive revolution. Automobile manufacturers as well as the fleet operators for heavy-duty vehicles are affected by the change from conventional to electric drivetrains and the resulting shift in the value chain. Among many available electrical vehicle technologies, the in-wheel drive topology offers a host of advantages. The vehicle manufacturers have been trying various options for this scenario and the axial-flux permanent magnet motors (AFPM) offer the most viable solution, suitable for being used as wheel hub motors. AFPMs in general promise higher power density and efficiency to their radial counterparts. This results in lower system weight for the same power requirement and in turn reduces the vehicle weight and total energy consumption. However, the technology has still not matured enough and is used sparingly for traction applications. Some major challenges faced by the AFPMs are the cooling of the stator/rotor unit, which limits the motor performance and the functional safety issues due to a large diameter leading to griding problems at higher rotational speeds. This paper discusses a novel approach for the active cooling of the stator unit of a single stator double rotor AFPM (SSDR-AFPM). For this purpose, various cooling concepts for the stator unit have been analyzed and constructed. Furthermore, the concepts were validated using a series of finite element simulations. The result was finally presented in a form of comparison matrix, based on different analyzed parameters. The results were derived from a research project currently being undertaken at the Chair of Production Engineering of E-Mobility Components at the RWTH Aachen University and is supported by the German Federal Ministry for Economic Affairs and Climate Action.