The electromagnetic performance of the soft magnetic core in manufactured electric machines is known to deviate significantly from datasheet values for the material used in the core. We quantify the discrepancy in permeability and losses between datasheet and physical units by calculating build factors for a typical hairpin IPM traction machine design. The derived build factors for losses are typically 1.5 at high frequency below 1 T, while approaching unity at flux densities approaching 2 T for all tested frequencies. At low frequency and low flux density, the loss build factor is peaking at 4. Permeability build factor starts at 0.6 at low flux density, dips to 0.35 at 1 T, and reaches unity at 1.5 T. All data used for this research is made available in the public domain.
Fyhr et al. (Wed,) studied this question.