Application of a Hybrid Modeling Approach for Eddy Current Estimation in Hairpin Windings

For traction motor applications, the hairpin winding technology with relatively large conductor cross section area is widely used. Compared to conventional stranded wire windings, increased eddy current losses may occur in the hairpin winding when the conductors are exposed to time varying magnetic fields. Although the additional losses due to the induced eddy currents are a well known phenomenon, classical calculation approaches reach their limits as soon as ferromagnetic material with nonlinear properties and complex shapes need to be considered. An accurate but time-consuming estimation consists of time-transient quasi-stationary finite element analysis (FEA). More efficiently, the induced eddy currents can be calculated by separating the conductors into parallel filaments following the partial equivalent electrical circuit (PEEC)approach. As long as linear material characteristics are prevailing; thus the problem can be solved in the frequency domain. In this paper, we propose the application of an hybrid FEA-PEEC modeling approach to estimate the eddy current losses in the conductors of a hairpin winding traction motor. For the proposed approach, the resulting linear system is solved in the frequency domain by direct solvers. To emphasize the benefit and the strength of the approach, a study case motor model is analysed and the results are assessed regarding the accuracy and the calculation time.