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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 inclu...
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... along the radial direction decreases, while the resistance along the thickness increases. Therefore, the reduced electromotive force with the approximately constant overall resistance results in a lower current density, and the eddycurrent losses reduce. The distribution of current density for the samples A and E at 5 Hz, 1.5 T is given in Fig. 8 for illustration. A 1-D eddy-current loss model would assume the sheet to be infinitely long in the radial direction, making it impossible to account for the above-mentioned ...
Citations
... The second approach to FE simulation involves the calculation of the distance to the cut edge, which is then used to obtain the local magnetization characteristics for each integration point in a continuous manner. To achieve enough accuracy, very fine meshes were used near the deteriorated edges with first-order elements in [11] and secondorder elements in [14], without further details on how the integration points and weights were selected. Due to the computational burden of using very fine meshes near the cut edge for certain geometries, the use of higher order elements with coarser meshes was proposed in [15] to reduce the computational time of the FE simulation of an induction motor with the inclusion of exponential deterioration profile. ...
... Due to the symmetry reasons, it is sufficient to solve (14) only for the positive region of the geometry (0 < < ), for which the analytical solution can be expressed as ...
This article proposes a novel methodology for incorporating electrical sheet cutting deterioration in electromagnetic finite-element simulations of energy conversion devices. While the existing methods account for the deterioration in the numerical integration either by increasing the mesh refinement or boosting the Gaussian quadrature order, the proposed method is based on the re-computation of quadrature weights and coordinates for a modeled deterioration, taking its explicit dependency into account. To validate the proposed method, numerical solutions are compared with electromagnetic analytical solutions in a beam geometry. A comprehensive analysis is then performed to evaluate the relative error, considering various model parameters. This analysis leads to a systematic procedure for selecting the optimal element size to achieve desired error levels. The procedure is successfully applied to a transformer geometry, and the computational performance of the proposed method is compared with the existing approaches through a time-stepping analysis. The results show that the proposed method is computationally more efficient than the existing approaches, and it eliminates the need to increase the mesh refinement or boost the order of the quadrature. It can be easily adapted for any type of deterioration profile.
... In [4], [5], the return path of the eddy currents were included and the eddy currents were modeled in 2D. In [6], a 2D axisymmetric finiteelement (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 2D FE modeling of the eddy currents provides highly accurate results and enables proper segregation of the losses. ...
... In this paper, we present a new analytical method to compute the eddy-current loss in thick laminations with a 2D 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 2D FE model presented in [7]. Afterwards, a time-domain eddy-current loss model is derived based on the analytical solution of 2D field problem. ...
... 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. ...
In this paper, 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 2D 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. Afterwards, a 2D analytical time-domain model is proposed for the eddy currents based on the solution of the 2D 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.
Eddy-current (EC) testing is one of the contactless nondestructive testing techniques for the physical property measurement (
e.g
. thickness, electrical conductivity and magnetic permeability) of steel plates in various industrial applications. In this study, an estimation method of plate thickness and permeability is proposed using the triple-frequency coil inductance with probe lift-off. The functional relationship between the plate properties, probe lift-off and characteristics of coil inductance is indicated by the simplified analytical model, which is employed for the initial guesses of optimisation. The proposed method can decrease the influence of the local minimum on property estimation. Numerical simulations and experiments have been performed to evaluate the proposed method with various plate properties and probe lift-off. Compared with the estimation results without the appropriate initial guesses, the proposed method is more robust and accurate for various cases, with a relative estimation error smaller than 8 %.
