Development of an Axial-Flux Permanent Magnet Machine with Directly Cooled Windings for a 48V-Mild-Hybrid Powertrain

Authors

Dipl.-Ing. C. Schwella, Assoc. Prof. Dr. techn. P. Hofmann, Institute of Powertrains and Automotive Technology (IFA), Vienna University of Technology; Dipl.-Ing. R. Morawetz, Dipl.-Ing. Dr. techn. D. Andessner, Dipl.-Ing. C. Sandner, Miba eMobility GmbH, Vorchdorf:

Year

2023

Print Info

Production/Publication ÖVK

Summary

The 48V electrical system allows to hybridise existing vehicle platforms at low cost, using e-machines with up to 30 kW power. At the Institute of Powertrains and Automotive Technology of the Vienna University of Technology, together with Miba eMobility, a compact axial flux machine (PMSM) with high torque density was developed, which was designed to be used as a traction motor in a P2-Mild-Hybrid System. The main focus was on the realisation of a stator cooling system in which the copper windings are directly immersed in the cooling medium water-glycol. This enables the integration into the cooling circuit of the combustion engine as well as a significantly higher performance and overload capability compared to conventional electric machines with jacket cooling.

To determine the e-motor specifications, in the vehicle simulation model e-motor parameters and cooling variants as well as the hybrid topology were varied and evaluated for their effects on the fuel consumption. During the development of the cooling concept, the flow of the coolant within the stator was defined and ageing tests were carried out, especially for the selection of a water-glycol resistant winding wire.

The direct winding cooling was investigated in stationary measurements and in dynamic driving cycles (WLTC, RTS95) on the electric motor test bench. It could be shown that the novel liquid cooling has a superior cooling performance compared to a conventional jacket cooling. Due to the outstanding heat dissipation properties of the direct water-glycol cooling, a compact machine design can be realised and in terms of fuel consumption reduction, the thermally unrestricted potential of the 48V-Mild-Hybrid System can be used.

ISBN

978-3-9504969-2-5