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To provide a discrete‐time nonlinear model for surface permanent‐magnet synchronous machines (SPMSMs) in order to discuss the stability of such machines.

Through differencing the co‐energy, obtained from a finite element method, the main flux path can be described by a complex reluctance. Furthermore, for a SPMSM, an equivalent circuit is presented that includes the eddy‐current losses and the voltage drops across stator resistance and leakage inductance. The model is transformed to a discrete‐time state‐space model by using a forward rectangular rule. By using a root locus technique, the stability of the new model is discussed.

From the calculated root locus it is concluded that the stability of a SPMSM is only guaranteed for certain values of the open loop gain. Moreover, by using the forward rectangular rule, it is concluded that a well‐considered time step has to be chosen.

The model considers the fundamental space harmonic components only. Moreover, the saturation of the leakage flux path is neglected.

As the model is formulated in discrete time, it can be used in modern drives where a digital controller is used.

This paper presents an equivalent electrical circuit for SPMSMs that takes into account the saturation of the magnetizing flux paths as well as the magnetic interaction between the two orthogonal magnetic axes.

Vibrations and acoustic noise are some of the fundamental problems in the design and exploitation of switched reluctance motors (SRMs). Adequate experimental and analysis methods may help to resolve these problems. This paper presents a theoretical analysis of the magnetic force distribution in SRM and a procedure for calculating the magnetic forces and the resulting vibrations based on the 2D finite element method. Magnetic field and force computations and a structural analysis of the stator have been carried out in order to compute the frequency spectrum of the generalized forces and displacements of the most relevant vibration modes. It is shown that for these vibration modes, the frequency spectrum can be predicted analytically. The theoretical and the numerical analyses have been applied to a 6/4 SRM and an experimental validation is presented.

To study the magnetic shielding of buried high‐voltage (HV) cables by adding conductive metal plates on the ground surface above the cables.

The field is calculated with eight rectangular conductive plates above the cables, positioned with their long edge either parallel to the cables or transversal to the cables. Here, the circuit method is used. In this method, the shield is replaced by a grid of straight filaments in which the unknown currents are searched by solving an electrical circuit.

It is observed from the calculation results that it is important to have a perfect electrical connection between adjacent plates. In the area above the shield, an “infinite” contact resistance between neighbouring plates results roughly in double field amplitude compared to the situation with contact resistance zero. The positioning of the rectangular plates (parallel or transversal to the cables) has not much influence on the shielding. The shielding efficiency as a function of the shield size is studied as well. The circuit method is validated by measurements on an experimental setup at reduced scale.

The circuit method is applied to conductive objects and not to ferromagnetic objects.

As the circuit method is rather fast also for 3D geometries with thin plates, the shielding of HV cables can be evaluated in a computationally more efficient way than by using, e.g. finite elements.

The circuit method is already described in the literature. The originality of this paper is the study – by this circuit method – of the effect of several parameters (size of the shield, contact resistance, orientation of the plates) on the shielding efficiency.

To study the magnetic shielding and the losses of non‐linear, hysteretic multilayered shields by using fast to evaluate analytical expressions.

In order to evaluate the shield in the frequency domain, the non‐linear shield is divided into a sufficient number of piecewise linear sublayers. Each sublayer has a permeability that is constant (space independent) and complex (to model hysteresis). This expression for the permeability is found from the Preisach model by a Fourier transform. Once H is known in the entire shield, analytical expressions calculate the eddy current losses and hysteresis losses in the material. The validity of the analytical expressions is verified by numerical experiments.

In the Rayleigh region, the shielding factor of perfectly linear material is better than the one of non‐linear metal sheets, but also the eddy current losses are higher. The results of the optimization show that steel is only a useful shielding material at low frequencies.

The analytical method is valid for infinitely long shields and for weak imposed fields in the Rayleigh region.

As the analytical expressions can be evaluated very fast (in comparison with slow finite elements models), many magnetic shields can be compared in parametric studies.

Analytical expressions exist for the shielding factor and the losses of linear materials. In this paper, the method is extended for non‐linear hysteretic materials. The effects of several parameters (material parameters, incident fields parameters) on the shielding and the losses are shown.

Flying‐capacitor multilevel converters (FCC) need a passive or active regulation of the capacitor voltages. Recently the trend is towards active control, often implemented separately from the current control. The advantages of a true multi‐variable control sparked the interest to apply Model Based Predictive Control (MBPC) for FCC. In this paper an objective analysis method to evaluate the effects of several design choices is presented. The effects of the weight factor selection, model simplification, and prediction horizon expansion for MBPC of a 3‐level FCC are analyzed in a systematical way.

The analysis is mainly based on the mean square error (MSE) of current and capacitor voltage. The results are analysed for different lengths of the prediction horizon and for a wide range of weight factor values. Similarly the effect of a model simplification, neglecting the neutral point voltage, is studied when implementing MBPC for FCCs while considering the computational aspects. Validation of the simulation results is done by experiments on an FPGA‐based setup.

Including the effect of the neutral point voltage considerably increases the current control quality and a much wider range of good values for the weight factor exists. As this good range is not critically dependent on the current amplitude it is possible to select one weight factor value for all operating points. Furthermore, it is concluded that increasing the prediction horizon increases the computational load without improving the control quality.

The effects of increasing the prediction horizon when including other controlled variables is to be investigated, as well as the robustness to modeling errors. The MSE analysis methodology is very suitable for this further research.

For practitioners of MBPC in power electronics the paper proves that by means of simulations and the MSE one value for weight factor can be chosen for all operating points. The paper clearly shows that a practical implementation is feasible and demonstrates that neglecting the neutral point voltage is not good practice.

The MSE‐based analysis is shown to be a systematical and unbiased methodology to evaluate the effects of design choices. The results from this analysis can be directly applied in practical setups.

To design an optimal active shield for the mitigation of the magnetic stray field around an induction heating device.

The active shield consists of several compensation coils in series and generates a counter field opposite to the main field. One extra compensation winding – the “generating compensation winding” (GCW) – is positioned close to the excitation coil and works as the secondary winding of a transformer. The power in this winding is used to drive the other compensation coils (the active shield), which are the load of the transformer. A circuit with passive components is inserted between the GCW and the other compensation coils. The shield is optimal if it achieves a high field reduction, while the energy dissipation is low. By using a genetic algorithm (GA) that minimizes an objective function, the optimization algorithm finds the optimal geometry and the optimal current for the GCW and the other compensation coils. The objective function uses time harmonic and axisymmetric finite element calculations.

The transformer driven active shield reduces the magnetic field effectively. It is cheap and easy to build, but it works well only for one frequency.

The shield is sensitive to tuning of the passive circuit and to changes in the frequency of the induction heater.

This transformer driven shield is an alternative for the classical active shield with external power supply.

An active shield that does not need an external power supply is a cheap solution for the shielding of magnetic fields.

In this paper a continuum description of deformable magnetized material including long‐range magnetic forces and magnetostriction is presented. Herein, magnetostriction and long‐range forces on the one hand, and magnetization and deformation on the other hand are considered simultaneously. Therefore, neither a strict distinction between the deformation due to magnetic forces and due to magnetostriction, nor a separation of the total free energy into magnetic and elastic energy is involved.

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.

The aim of the paper is to present a simple approach to modelling minor hysteresis loops in grain‐oriented steel sheets under quasi‐static and dynamic conditions. The hysteresis phenomenon is described with a recently developed hybrid model, which combines ideas inherent in the product Preisach model and the Jiles‐Atherton description. The dynamic effects due to eddy currents are taken into account in the description using a lagged response with respect to the input.

It is assumed that some model parameters might be dependent on the level of relative magnetization within the material. Their dependencies could be given as power laws. The values of scaling coefficients in power laws are determined.

A satisfactory agreement of experimental and modelled quasi‐static and dynamic hysteresis loops is obtained.

The present study provides a starting point for further verification of the approach for other classes of soft magnetic materials, which could be described with the developed model. At present, the approach to model minor loops by the update of model parameters is verified for the B‐sine excitation case.

The “branch‐and‐bound” optimization algorithm is a useful tool for recovery of the values of both model parameters and scaling coefficients as well.

The recently developed hybrid description of hysteresis phenomenon can be successfully extended to take into account symmetric minor loops. The developed approach could be a framework to develop a comprehensive description of magnetization phenomena in the future.

Due to the increasing amount of high power density high-speed electrical machines, a detailed understanding of the consequences for the machine’s operational behaviour and efficiency is necessary. Magnetic materials are prone to mechanical stress. Therefore, this paper aims to study the relation between the local mechanical stress distribution and magnetic properties such as magnetic flux density and iron losses.

In this paper, different approaches for equivalent mechanical stress criteria are analysed with focus on their applicability in electrical machines. Resulting machine characteristics such as magnetic flux density distribution or iron are compared.

The study shows a strong influence on the magnetic flux density distribution when considering the magneto-elastic effect for all analysed models. The influence on the iron loss is smaller due to a high amount of stress-independent eddy current loss component.

The understanding of the influence of mechanical stress on dimensions of electrical machines is important to obtain an accurate machine design. In this paper, the discussion on different equivalent stress approaches allows a new perspective for considering the magneto-elastic effect.