Search results

Finite element discretizations of low‐frequency, time‐harmonic magnetic problems lead to sparse, complex symmetric systems of linear equations. The question arises which Krylov subspace methods are appropriate to solve such systems. The quasi minimal residual method combines a constant amount of work and storage per iteration step with a smooth convergence history. These advantages are obtained by building a quasi minimal residual approach on top of a Lanczos process to construct the search space. Solving the complex systems by transforming them to equivalent real ones of double dimension has to be avoided as such real systems have spectra that are less favourable for the convergence of Krylov‐based methods. Numerical experiments are performed on electromagnetic engineering problems to compare the quasi minimal residual method to the bi‐conjugate gradient method and the generalized minimal residual method.

The electromagnetic excited audible noise of electrical machines can be mostly attributed to radial forces on stator tooth‐heads. The methodology proposed in this paper uses numerical field simulation to obtain the magnetic air gap field of electrical machines and an analytical‐based post‐processing approach to reveal the relationship between air gap field harmonics and the resulting force wave.

The simulated air gap field is sampled in space and time and a two‐dimensional Fourier transform is performed. The convolution of the Fourier transformed air gap field by itself represents a multiplication in space time domain. During the convolution process, all relevant combinations of field waves are stored and displayed using space vectors.

The effectiveness of the proposed approach is shown on an example machine. Particular examples of individual force waves demonstrate how the approach can be used for practical application in analysis of noise and vibration problems in electrical machines. The proposed method is compared to the result of a Maxwell stress tensor calculation. It shows that the deviation is small enough to justify the approach for analysis purposes.

The combination of analytically understood force waves and the use of numerical simulation by means of air gap field convolution has not been proposed before.

To retain small models, electrostatic and electrokinetic finite element formulations are linked with several field‐circuit couplings and floating potential constraints. The approaches enable convenient simulations of a condenser bushing and a dielectric heating device.

Disturbing vibrations and noise of electrical machines are gaining impact. The paper aims to focus on the necessity of estimating the electromagnetic, structure‐dynamical, and acoustic behaviour of the machine during designing and before proto‐typing.

An adequate tool is numerical simulation applying the finite‐element method (FEM) and the boundary‐element method (BEM) allowing for the structured analysis and evaluation of audible noise also caused by manufacturing tolerances.

The simulated results show good accordance to measurement results. The methods and simulation tools allow the analysis and evaluation of every type of energy converter with respect to its electromagnetic, structure‐dynamical and acoustic behaviour.

The methods developed and proved can be applied to any electromagnetic device in general.

The purpose of this paper is to present a method for analyzing higher magnetic force harmonics in electrical machines based on electromagnetic finite element simulation.

Sampling of air gap field solution data allows for a Fourier decomposition of magnetic forces and flux densities. A two‐dimensional convolution gives insight into the spectral decomposition of forces responsible for acoustic noise, vibration and higher torque harmonics.

The proposed approach seems especially suitable for synchronous machine models. The influence of magnetic circuit design parameters that are difficult to calculate analytically on the harmonic air gap content can be analyzed and the spectral force decomposition illustrated by means of space vectors.

The approach is generalized to the convolution and analysis of arbitrarily sampled two‐dimensional data in this paper.

This paper presents a methodology to achieve a global dynamic model of an electrical system that consists of a battery, an inverter, a permanent magnet servo motor and a turbine. The stress is placed on the fact that a classical finite element model would not be able to provide a satisfactory representation of the transient behaviour of the whole system. A staged modelling is proposed instead, which succeeds in providing a complete picture of the system and relies on numerous finite element computations.

The purpose of this paper is to analyse the accuracy of the thrust force of a linear actuator computed with different finite elements models.

A series of 2D and 3D models corresponding to different levels of approximation of the original problem are considered. A reliable error estimator based on dual magnetostatic formulations is used.

A 3D model does not necessarily ensure more accurate results than a 2D model. Because of limitations on the number of mesh elements, the discretisation error in 3D can be of the same order of magnitude as the error introduced by the 2D approximation.

The results emphasise the need to consider errors arising from different simplifications with respect to one another, in order to avoid improvements of the model increasing the complexity but not improving the accuracy of the results.

A finite element analysis of a permanent magnet transverse flux linear actuator is presented. In this application where we need a small model (for optimisation purposes) as well as a high accuracy on the computed force, we propose to combine several models with different levels of size and complexity, in order to progressively elaborate an accurate, but nevertheless tractable, model of the system.

The purpose of this paper is to present an experimental setup for the verification of coupled electromagnetic field‐circuit simulation, called TESTCASE. By means of simple and well‐defined geometries, the comparison of different coupling approaches among each other and with measurements should be possible.

The physical setup consists of a C‐core in conjunction with a reluctance rotor. The TESTCASE is designed to work in static operation and with motion induced voltage.

Simulation results using different approaches as well as measurement results are presented. Practical issues in measurement and simulation are discussed. It was found that particular care has to be taken concerning the modeling of the air around the TESTCASE structure.

With the proposed approach, it is possible to evaluate the coupled field circuit problem on a defined and well‐known geometry. Simulation results can be compared to measurements.

The magnetic and mechanical finite element systems are combined into one magnetomechanical system. Investigating the coupling terms results in a finite element expression for the magnetic forces (Lorentz force and reluctance force) for both the linear and nonlinear case. The material deformation caused by magnetostriction is represented by an equivalent set of mechanical forces, giving the same strain to the material as magnetostriction does. The resulting magnetostriction force distribution is superposed onto other force distributions (external mechanical forces, magnetic forces) before starting the mechanical deformation or vibration analysis. This procedure is incorporated into a weakly‐coupled cascade solving of the magnetomechanical problem.