New Subdomain Technique for Electromagnetic Performances Calculation in Radial-Flux Electrical Machines Considering Finite Soft-Magnetic Material Permeability

The most significant assumption in the subdomain technique (i.e., based on the formal resolution of Maxwell's equations applied in subdomain) is that the iron parts are considered to be infinitely permeable, so that the saturation effect is neglected. In this paper, we present a novel contribution on improving this 2-D technique in polar coordinates by focusing on the consideration of iron relative permeability. In non-periodic regions, magnetostatic Maxwell's equations are solved considering non-homogeneous Neumann boundary conditions, and the general solution is obtained by applying the interfaces conditions in both directions (i.e., r- and theta-edges ICs). The proposed model is relevant for different types of radial-flux electrical machines with(out) permanent magnets (PMs) supplied by a direct or alternate current (with any waveforms). For example, the semi-analytical model has been implemented for spoke-type PM machines. The magnetic field calculations have been performed for two different values of iron core relative permeability (viz, 100 and 600), and compared with those obtained by the 2-D finite-element method. The semi-analytical results are in a very good agreement with those obtained numerically, considering both amplitude and waveform.