A Method of Deriving an Equivalent Permeability Spectrum of Ferrous Materials Considering All Effects in Electrical Machines for 2-D Magneto-Dynamic Simulations

In this article, a method is developed to calculate an equivalent permeability spectrum of ferrous materials in the context of electrical machines. Compared with the complex permeability in the literature, the calculated equivalent permeability considers all practical effects in electrical machines besides eddy current influences in the electrical steel. The equivalent permeability is calculated using the phase inductance of electrical machines. However, due to parasitic capacitance's influence in electrical machines, the phase inductance spectrum cannot be directly measured. In order to solve the problem, a grey box method is applied to model electrical machines in a wide frequency range. Then, all electrical components related to the parasitic capacitors are removed from the grey box model, and the remaining electrical circuit is used to determine the phase inductance spectrum without the parasitic capacitors' influence. Finally, the phase inductance spectrum calculated from the grey box model is compared with the FEM-simulated inductance spectrum to search for the equivalent permeability in a wide frequency range. Since the phase inductance spectrum contains all practical effects in electrical machines, the calculated equivalent permeability also includes these effects. The searched equivalent permeability can be used for 2-D magneto-dynamic simulations, whose results are required for parametrizing the white box models.