Iron losses in laser-cut toroidal samples of 12 mm thick steel laminations used in large synchronous motors are studied. Eddy currents in the lamination cross-section are solved with the 2-D finite element method while applying a constitutive law based on the Jiles-Atherton hysteresis model. The effect of cutting on the material properties is included by a continuous local material model approach, which enables to express the material properties as a function of distance from the cutting edge. The accuracy of the model is validated by comparing the simulations and experimental measurements of five toroidal samples assembled from concentric rings with different widths. Highly accurate results are obtained in terms of both the matching of B-H loops and the total loss values with an average relative error less than 2.9%. The results show that the hysteresis loss under quasi-static excitation increases up to 20.4% due to the effect of cutting. It is observed that the eddy-current loss becomes dominant over the hysteresis loss even at 5 Hz, and this eddy-current loss decreases up to 72.5% as the number of concentric rings increases. The presented model and the results accurately show how iron losses occur in thick materials and how they are affected by the cutting process.INDEX TERMS Cutting, eddy currents, hysteresis, iron loss, skin effect, thick materials.

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In this work, we study how the deterioration caused by electrical steel sheet cutting can be implemented in finiteelement simulation of electrical machines in an effective manner. We use exponential decay as the degradation profile and propose a new method for the numerical integration using Gauss-Jacobi quadratures. The method is tested for 1-D case, and highly accurate results are obtained.

Finite element analysis of transformers with stranded conductors can be computationally heavy due to the fine mesh required for winding domains. In this paper, a domain decomposition method with subdomain pre-processing is proposed to overcome with this problem. In order to solve the field-circuit problem with finite element analysis, the winding domain is modelled initially. Next, the reduced matrix system is obtained from the winding domain formulation. The solution of the entire problem is obtained by solving the winding domain formulation and the reduced matrix system separately. The method is tested on a transformer model in no load operation. Accurate solutions are obtained in both frequency and time domains 7-9 times faster than when using brute-force method.

In this article, we propose an analytical method to compute the eddy-current loss in nonlinear thick steel laminations (3-12 mm) by considering the return path of the eddy currents. Initially, a 2-D finite-element (FE) model is applied to segregate losses measured from toroidal material samples into hysteresis and eddy-current loss components to use them as reference. Afterward, a 2-D analytical time-domain model is proposed for the eddy currents based on the solution of the 2-D field problem. The time-domain model is then used to derive a simple frequency-domain eddy-current loss formulation for the sinusoidal flux density case with the inclusion of a skin-effect correction factor, which accounts for the nonlinearity of the material. Highly accurate results are obtained from the proposed model compared to FE reference results with a mean relative error of 5.1% in the nonlinear region.