Dries Vanoost

Removing the Spectral Leakage in Time-Domain Based Near-Field Scanning Measurements

This paper describes the application of a new and easy to implement algorithm to EMI near-field scanning measurement results obtained with a time-domain-based measurement system. The algorithm aims to reduce the effect of spectral leakage on amplitude and phase of the measured field components. The proposed algorithm significantly increases the accuracy of the measured electromagnetic near field with a limited extra computational cost. The versatility and effectiveness of the proposed algorithm is shown on both simulated and measured data. It is shown that for situations with one single frequency component or with several well-separated frequency components, the algorithm is as performant as the application of a flat top window and outperforms other types of windows. However, as soon as the frequency components approach each other implying their spectral leakage patterns overlap, the proposed algorithm outperforms the application of a flat top window.

Two-Dimensional Magnetostatic Finite-Element Simulation for Devices With a Radial Symmetry

This paper proposes a 2-D magnetostatic finite-element solver for radially symmetric devices, complementary to the standard Cartesian and axisymmetric solvers, which are typically used for translatory and cylindrically symmetric configurations. In contrast to the Cartesian and axisymmetric cases, a specific difficulty is encountered due to the particular dependence of the magnetic vector potential on the radial coordinate caused by the requirement for radial symmetry. Dedicated finite-element shape functions are developed such that the partition-of-unity property, consistency, and convergence of the formulation are guaranteed. Implementation aspects and modeling peculiarities are discussed. The new solver is validated for models in which analytical solutions exist. The modeling accuracy of the new 2-D solver is compared with a 3-D model for the calculation of the electromotive force and the electromagnetic torque of a twin-rotor axial-flux permanent magnet synchronous machine.

Embedding a Magnetoelastic Material Model in a Coupled Magnetomechanical Finite-Element Solver

This paper proposes a magnetomechanical 2-D finite-element solver embedding an energy-based material model. The energy-based material model determines the value of the permeability tensor in each material point of the computational grid based on the material data, the magnetic field strength, and the mechanical stress. The simulation results are compared with the measurement data for a nickel I-beam benchmark.

Grain scale hysteresis model embedded in a multi-scale material model

Reliable and accurate models of ferromagnetic materials are essential for designers of electrical machines and transformers to maximize the efficiency and power density, as well as for material-science engineers engaged in the optimization of morphological properties of electrical steels such as texture and grain size. These models have to consider magnetic as well as mechanical influences and their interdependence.

Nonlinear Magnetostatic Finite-Element Formulation for Models With Radial Symmetry

This paper discusses the implementation of nonlinear material properties in a 2-D magnetostatic finite-element solver for radially symmetric models. It is shown that, when saturation occurs, the particular dependence of the magnetic vector potential on the radial coordinate as required for radial symmetry is lost. Despite the 2-D geometrical symmetry, the weighted residual approach requires numerical quadrature points to be distributed along the direction of symmetry. The 2-D solver with radial symmetry is shown by calculating the performance of a dual-rotor permanent-magnet axial-flux machine.

An Iterative Interpolated DFT to Remove Spectral Leakage in Time-Domain Near-Field Scanning

Time-domain near-field scanning is gaining more and more interest within EMC engineering to analyze electromagnetic near-fields of, e.g., quasi-stationar devices. When using a digital oscilloscope to scan the near-fields of an electronic device, the oscilloscope measures time-domain signals that comprise in most cases a large number of frequency components. For many of these components, noncoherent sampling occurs, resulting in spectral leakage when calculating the frequency spectrum of the time-domain signals with the discrete Fourier transform. This paper proposes an improved method to detect the presence of such noncoherently sampled signals as well as an iterative algorithm to obtain accurate approximations of all the frequency components with their accompanying amplitudes and phase angles. The algorithm excels over existing algorithms in obtaining these values especially in situations where several sinusoidal components are close to each other in the spectrum. This is achieved, thanks to an iterative process of removing the influence of the multiple sinusoidal components on each other. This paper contains the mathematical description of the algorithm and a numerical example evaluating the accuracy of the algorithm. The algorithm has a higher accuracy than the existing approaches, e.g., multipoint Interpolated Discrete Fourier Transform (IpDFTs), with only a slight increase of the computational cost.

Influence of sample shape and size on the shielding effectiveness of EMI when characterized with the stripline test method

This paper studies the influence of a gaskets shape and size on its high-frequency shielding-effectiveness as measured with the stripline test method. Based on full-wave simulations it is shown that the main influencing parameter for the shielding-effectiveness is the gaskets conductivity. Through a comparison with the reverberation room method, it is shown that differences due to shape and size of the gasket are not related to the stripline set-up, but are a reflection of the true shielding effectiveness of the gasket.

Design, simulation and use of an energy harvester based on a permanent magnet synchronous generator

A wind energy harvester, containing a synchronous radial flux generator, has been designed and tested. The energy harvester, which feeds a decentralized control unit of a ventilation system, has been simulated using MATLAB and FEMM software. A prototype has been built and voltage, power and efficiency measurements have been performed. In order to increase the efficiency and to obtain a cheap and (almost) maintenance free generator, a dual rotor containing permanent magnets and an ironless stator has been used.