Finite-Element Modeling and Characterization of Iron Losses in 12 mm Thick Steel Laminations Including the Effect of Cutting

Abstract

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.

2-D Analytical Model for Computing Eddy-Current Loss in Nonlinear Thick Steel Laminations

“…Magnetic measurements were carried out in the range of 0.5-1.5 T magnetization levels, for the quasi-static and sinusoidal excitation cases at 5 and 10 Hz, and the iron loss density was calculated from the measured quantities. The measurement system is described in [7] in detail.…”

“…This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ The 2-D axisymmetric FE model presented in [7] is used for identification of material parameters and simulation of the total losses based on the measurement results. The model considers the cross section of the lamination in the r z plane, along which the current density J is aligned.…”

“…The defined problem is solved numerically in a MATLAB-based in-house code by using T formulation with a constitutive material law based on scalar Jiles-Atherton (JA) hysteresis model [11]. The details of the formulation of the model and the solution procedure is presented in [7]. The total losses p tot are simulated with a mean relative error of 4.1% against the measurements for the average magnetic flux density B m levels between 0.5 and 1.5 T as shown in Fig.…”

“…In [4] and [5], the return path of the eddy currents were included and the eddy currents were modeled in 2-D. In [6], a 2-D axisymmetric finite-element (FE) model along the lamination cross section with a hysteretic constitutive law was presented, and this model was developed further in [7] by including the effect of cutting for 12 mm thick laminations. These studies showed that 2-D FE modeling of the eddy currents provides highly accurate results and enables proper segregation of the losses.…”

“…In this article, we present a new analytical method to compute the eddy-current loss in thick laminations with a 2-D approach and accounting for the skin effect in the lamination cross section. For this purpose, the eddy-current loss for the studied samples is segregated using a 2-D FE model presented in [7]. Afterward, a time-domain eddy-current loss model is derived based on the analytical solution of 2-D field problem.…”