Search results

This paper aims to introduce a computationally efficient hybrid analytical–finite element (FE) methodology for loss evaluation in electric vehicle (EV) permanent magnet (PM) traction motor applications. In this class of problems, eddy current losses in PMs and iron laminations constitute an important part of overall drive losses, representing a key design target.

Both surface mounted permanent magnet (SMPM) and double-layer interior permanent magnet (IPM) motor topologies are considered. The PM eddy losses are calculated by using analytical solutions and Fourier harmonic decomposition. The boundary conditions are based on slot opening magnetic field strength tangential component in the air gap in the SMPM topology case, whereas the numerically evaluated normal flux density variation on the surface of the outer PM is implemented in the IPM case. Combined analytical–loss evaluation technique has been verified by comparing its results to a transient magnetodynamic two-dimensional FE model ones.

The proposed loss evaluation technique calculated the total power losses for various operating conditions with low computational cost, illustrating the relative advantages and drawbacks of each motor topology along a typical EV operating cycle. The accuracy of the method was comparable to transient FE loss evaluation models, particularly around nominal speed.

The originality of this paper is based on the development of a fast and accurate PM eddy loss model for both SMPM and IPM motor topologies for traction applications, combining effectively both analytical and FE techniques.

Several formulations have been developed solving 3D eddy current problems by the Finite element method based on vector quantities. Scalars, involving only one unknown per node of the mesh seem to be, however, more efficient. A particular scalar potential formulation has already been developed which is able to handle 3D magnetostatics,. This technique has been extended for cases involving eddy currents developed at low frequencies, where the skin effect can be neglected.

The design of several electromagnetic devices, such as magnets and transformers, leads to a 3D magnetostatic field analysis. Although such problems can be solved by using vector potential formulations, scalar potential techniques seem to be more efficient because of the reduced number of unknowns they introduce. Even these methods, however, present certain drawbacks, depending on the way the scalar potential is defined: considerable cancellation errors in iron parts, difficulties to simulate multiply connected iron cores, a complicated way to compute a source field distribution.

Some problems involve eddy currents developed in thin skin effect depths and a numerical analysis, based on the classical finite element method, is extremely laborious and expensive. Although such situations lead to operations concerning the linear part of the material characteristics, the related geometries are not, usually, simple enough to permit an analytical solution. The present work is based on a new type of element enabling efficient modeling in such cases. It combines the increased accuracy and speed of analytical solutions for large subdomains, a reduced number of unknowns and the advantages of functional minimization procedures.

This paper aims to present an accurate representation of laminated wound cores with a low computational cost using 2D and 3D finite element (FE) method.

The authors developed an anisotropy model in order to model laminated wound cores. The anisotropy model was integrated to the 2D and 3D FE method. A comparison between 2D and 3D FE techniques was carried out. FE techniques were validated by experimental analysis.

In the case of no‐load operation of wound core transformers both 2D and 3D FE techniques yield the same results. Computed and experimental local flux density distribution and no‐load loss agree within 2 per cent to 6 per cent.

The originality of the paper consists in the development of an anisotropy model specifically formulated for laminated wound cores, and in the effective representation of electrical steels using a composite single‐valued function. By using the aforementioned techniques, the FE computational cost is minimised and the 3D FE analysis of wound cores is rendered practical.

The paper presents a procedure for the design of claw pole alternators for small scale wind power applications. The method involves a preliminary design stage by means of the classical magnetic circuit analysis and a detailed design stage involving a 3D finite element model. This technique has been implemented in the design of a multiple generation for a small scale gearless autonomous system. The developed model can be implemented for the optimization of the rotor claw geometry through a minimization algorithm.

This paper aims to the improvement of permanent magnet shape in the popular permanent magnet synchronous machine (PMSM) is proposed in this paper in view to mitigate cogging torque magnitude and torque ripple.

A two-dimensional exact analytical approach of magnetic field distribution is established for the PMSM considering magnet shape and slot opening. The optimal magnet shape is constituted of small number of layers stacked radially. The thickness of each magnet layer is considered equal to about one mm or more; however, a parametric study was performed to determine pole pitch ratio value. The finite element method is used to validate the analytical results.

Cogging torque peaks and torque ripples can be mitigated significantly more than 90 per cent compared to results issued from machine having classical magnet shape. Raising the number of magnet layers can give better results. The results of this paper are compared also with those issued from the machine having sinusoidal magnet shape and give a good solution.

A new technique for cogging torque and torque ripple mitigation is proposed in this paper by changing permanent magnet shape. The proposed final magnet shape is constituted of a set of stacked and well-dimensioned layers relative to the opening angle.

The purpose of this paper is to present the application of the loss approximation method for non-oriented electrical steel developed by the authors. A new model of a toroidal sample with dimensions ensuring high uniformity of the field was presented.

A critical analysis of the methods used was carried out. Based on these considerations, the authors proposed their own loss approximation method, which allows obtaining high accuracy in a wide range of induction and frequency. The proposed method is based on the assumption that for a certain frequency range losses can be describe by two terms formula. For a fixed value of the peak flux density Bm, the graph of specific loss divided by the frequency should have the form of a straight line. Then, the obtained coefficients for different Bm are the basis for approximation with the power function.

The comparison of measurement and approximation results shows that the method allows to obtain very good accuracy in a wide range of induction and frequency.

More detailed studies on the impact of cutting on a larger number of samples with different geometrical dimensions are needed.

Application of the new method provides a better approximation of the curve of the loss and thus a more accurate calculation of the core loss in the electrical machines.

The paper presents the application of the loss approximation method for non-oriented electrical steel developed by the authors. A new model of a toroidal sample with dimensions ensuring high uniformity of the field was presented. It is shown that the approximation introduced allows for high accuracy in a wide range of frequency and magnetic flux density.

This paper aims to provide a new method of generating relatively accurate and smooth saturated B-H curves based on reliable measurement data to improve the accuracy and efficiency of electromagnetic simulation.

The characteristics of different B-H curve extrapolation models are summarized, and an improved method is proposed. The fitting procedure in low fields and extrapolation procedure in high fields are presented in detail. The saturated B-H curves generated by various methods are compared and discussed. Finally, a simulation case study proved the advantages of the new method in terms of simulation accuracy and efficiency.

The B-H curve created by the new method avoids extrapolation from a single point and simultaneously smoothens the entire B-H curve, thereby improving the simulation accuracy and efficiency. The low magnetic potential requirements for closed measurements and the small deviation with open measurements indicate that this method is well-suited for implementation.

The results are applicable for materials subject to such excitation levels that saturation has to be taken into account.

While some extrapolation models of B-H curves have been investigated in reference papers, there is still room for improvement in accuracy and smoothness. The new method processes low fields and high fields magnetization data and then connects them based on third-order boundary equations for the first time. This method can generate saturated B-H curves with good accuracy and smoothness while retaining outstanding operability.

This paper aims to propose a novel direct method for indefinite algebraic linear systems. It is well adapted for sparse linear systems, such as those of two-dimensional (2-D) finite elements problems, especially for coupled systems.

The proposed method is developed on an example of an indefinite symmetric matrix. The algorithm of the method is given next, and a comparison between the numbers of operations required by the method and the Cholesky method is also given. Finally, an application on a magnetostatic problem for classical methods (Gauss and Cholesky) shows the relative efficiency of the proposed method.

The proposed method can be used advantageously for 2-D finite elements in stepping methods without using a block decomposition of matrices.

This method is advantageous for direct linear solving for 2-D problems, but it is not recommended at this time for three-dimensional problems.

The proposed method is the first direct solver for algebraic linear systems proposed since more than a half century. It is not limited for symmetric positive systems such as many of direct and iterative methods.