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Permanent magnet passive magnetic bearings (PMBs) are used for suspension of rotating shafts in one direction. PMBs with alternating radially magnetized rings having back iron is one of the most optimum configurations among all configurations of PMBs. This paper aims to investigate the effect of the conductivity and permeability of these back irons on the stiffness and damping of the configuration.

The stiffness and damping of the configuration will be calculated through a 2D dynamic analytical method and validated by FEM simulations.

The results of the paper show how the permeability and conductivity of the back irons can affect stiffness and damping of PMB. Furthermore, the size of the magnets and the air intervals between them are optimized for maximum stiffness and damping.

The results show that these bearings can have some intrinsic damping without any loss of stiffness, which can be useful for many applications.

A new type of variable damping viscous damper is developed to meet the settings of different damping parameter values at different working stages. Its main principle and design structure are introduced, and the two-stage and multi-stage controllable damping methods are proposed.

The theoretical calculation formulas of the damping force of power-law fluid variable damping viscous damper at elongated holes are derived, aiming to provide a theoretical basis for the development and application of variable damping viscous dampers. For the newly developed variable damping viscous damper, the dynamic equations for the seismic reduction system with variable damping viscous dampers under a multi-degree-of-freedom system are established. A feasible calculation and analysis method is proposed to derive the solution process of time history analysis. At the same time, a program is also developed using Matlab. The dynamic full-scale test of a two-stage variable damping viscous damper was conducted, demonstrating that the hysteresis curve is complete and the working condition is stable.

Through the calculation and analysis of examples, the results show that the seismic reduction effect of high and flexible buildings using the seismic reduction system with variable damping viscous dampers is significant. The program developed is used to analyze the seismic response of a broadcasting tower using a variable damping TMD system under large earthquakes. The results indicate that the installation of variable damping viscous dampers can effectively control the maximum inter-story displacement response of TMD water tanks and can effectively consume seismic energy.

This method can provide a guarantee for the safe and effective operation of TMD in wind and vibration control.

An overview is given on design features, numerical modelling and testing of a novel electromagnetic actuator to achieve a controllable stiffness to be used as a device for parametric stiffness excitation.

In principle, the actuator consists of a current driven coil placed between two permanent magnets. Repellent forces are generated between the coil and the magnets, centering the coil between the two magnets. The 2D finite element analyses are carried out to predict the forces generated by this arrangement depending on coil current and coil position. Force measurements are also made using the actual device.

Actuator forces as predicted by the finite element analyses are in excellent agreement with the measured data, confirming the validity of the numerical model. Stiffness of the actuator is defined as the increase of force per unit of coil displacement. Actuator stiffness depends linearly on the coil current but in a nonlinear manner on the coil displacement. The performance of the actuator is sufficient to demonstrate the effect of a so‐called parametric anti‐resonance on a test stand.

Although the performance of the actuator is satisfactory, there is potential for further improvement of the actuator design.

This paper reports for the first time on an electromechanical device to create a time‐periodic stiffness variation to be used for research in the field of parametrically excited mechanical systems. The device is used to prove experimentally an effect to suppress mechanical vibrations which has been studied so far only in theoretical studies.

The purpose of this paper is to implement and test a 1D eddy‐current model for laminated iron core of electrical machines and investigate the possibility of incorporating it in a 2D FE analysis.

The 1D eddy‐current model of laminated core is extended to handle rotating‐field problems and coupling between the x‐ and y‐components of the magnetic field. Explicit coupling terms are introduced in the Jacobean matrix to ensure convergence and time efficiency. The procedure is computationally tested for both the case where there is no feedback to the 2D FE and the case where the results of the eddy‐current model were fed‐back to the 2D analysis.

The coupling terms ensured fast and robust convergence. The incorporation of the eddy‐current model in the 2D FE analysis is possible, provided some under‐relaxation is used to ensure the convergence of the overall 1D‐2D procedure.

The method has been computationally tested with 2D like procedure corresponding to a 2D model with only one element. The behaviour of the model in actual 2D computation presents some problems related to the convergence of the overall procedure and they have been dealt with in another publication.

The paper is of practical value for designers of electrical machines. On one hand, the model can be used a posteriori to estimate eddy‐current losses in iron stacks, and on the other hand it can be incorporated into 2D FE analysis including the losses in the field solution and enhancing its power and energy balance.

The theory is presented of the increase in damping that can be obtained when a damping compound is added to a simple structure vibrating in a bending mode. Consideration has been given to the use of ‘Aquaplas’ damping compound on a vibrating stringer‐skin combination, and it has been shown that the maximum damping ratio is obtained when the material is applied to the stringer flange over the centre 40 per cent of the pin‐ended length of the beam. A preliminary experimental investigation is described, in which damping measurements were made on a simple structural specimen treated with Aquaplas. A new method was used successfully to determine the damping ratio of a heavily damped system. The damping properties of Aquaplas were evaluated, and some of the theoretical conclusions were verified. Some of the results obtained indicate that a more accurate mathematical representation must be sought for the visco‐elastic behaviour of Aquaplas than is provided by the ‘complex stiffness’ method.

This paper aims to give a perspective about the variety of techniques which are available and are being further developed in the area of coupled field formulations, with selective bibliography and practical examples, to help postgraduate students, researchers and designers working in design or analysis of electrical machinery.

This paper reviews the recent trends in coupled field formulations. The use of these formulations for designing and non‐destructive testing of electrical machinery is described, followed by their classifications, solutions and applications. Their advantages and shortcomings are discussed.

The paper gives an overview of research, development and applications of coupled field formulations for electrical machinery based on more than 160 references. All landmark papers are classified. Practical engineering case studies are given which illustrate wide applicability of coupled field formulations.

Problems which continue to pose challenges to researchers are enumerated and the advantages of using the coupled‐field formulation are pointed out.

This paper gives a detailed description of the application of the coupled field formulation method to the analysis of problems that are present in different electrical machines. Examples of analysis of generators and transformers with this formulation are presented. The application examples give guidelines for its use in other analyses.

The coupled‐field formulation is used in the analysis of rotational machines and transformers where reference data are available and comparisons with other methods are performed and the advantages are justified. This paper serves as a guide for the ongoing research on coupled problems in electrical machinery.

This paper aims to propose a new 3D electromagnetic model to compute translational motion eddy current in the conducting plate of a novel linear permanent magnet (PM) induction heater. The movement of the plate in a DC magnetic field created by a PM inductor generates induced currents that are at the origin of a heating power by Joule effect. These topologies have strong magnetic end effects. The analytical model developed in this work takes into account the finite length extremity effects of the conducting plate and the reaction field because of induced currents.

The developed model is based on the combination of the sub-domain’s method and the image’s theory. First, the magnetic field expressions because of the PMs are obtained by solving the three-dimensional Maxwell equations by the method of separation of variables, using a magnetic scalar potential formulation and a magnetic field strength formulation. Then, the motional eddy currents are computed using the Ampere law, and the finite length extremity effects of the conducting plate are taken into account using the image’s method. To analyze the accuracy of the proposed model, the obtained results are compared to those obtained from 3D finite element model (FEM) and from experimental tests performed on a prototype.

The results show that the developed analytical model is very accurate, even for geometries where the edge effects are very strong. It allows directly taking into account the finite length extremity effects (the transverse edge effects) of the conducting plate and the reaction field because of induced currents without the need of any correction factor. The proposed model also presents an important reduction in computation time compared to 3D finite element simulation, allowing fast analysis of linear PM induction heater.

The proposed electromagnetic analytical model can be used as a quick and accurate design tool for translational motion PM induction heater devices.

A new 3D analytical electromagnetic model, to find the induced power in the conducting plate of a novel translational motion induction heater has been developed. The studied heating device has a finite length and a finite width, which create edge effects that are not easily considered in calculation. The novelty of the presented method is the accurate 3D analytical model, which allows finding the real power heating and real distribution of the induced currents in the conducting plate without the need to use correction factor. The proposed model also takes into account the reaction field because of induced currents. In addition, the developed model improves an important reduction in the computation time compared with 3D FEM simulation.

The purpose of this paper is the development of a new numerical method for the calculation of the air-gap magnetic flux harmonics in synchronous machines with permanent magnet (PM) excitation. The harmonic analysis results are used as input data for the eddy-current loss calculation and for the rotor heating evaluation.

The method is based on the finite element analysis (FEA). The model takes into account toothed stator design, rotor asymmetrical magnetic reluctance and saturation. At first, a series of static DC magnetic (magnetostatic) simulations is run. Each problem corresponds to specific rotor position and the momentary stator winding currents. The Fourier analysis performed for each problem yields the harmonic spectrum variation in time. Then, a series of AC magnetic (time-harmonic) simulations is run. Each problem corresponds to a specific harmonic. The result is the eddy-current losses distribution. After total loss is calculated, the heat transfer analysis is conducted.

The analysis reveals that 90 per cent of losses are located in the sleeve that holds PMs together. Rotor eccentricity brings even harmonics of low magnitude that have little impact on heating.

In general, the study requires transient electromagnetic analysis with motion. The purposed method allows to simplify the problem. The method is based on static and quasi-static (time-harmonic) problems simulation. It is fast and highly automated. The method allows simultaneous taking into account of tooth-order harmonics, stator winding harmonics and eccentricity for heating calculation.

The purpose of this paper is to investigate the lateral forces during the fall of a magnet in a conducting pipe, when the direction of magnetization of the magnet is fixed. If the direction of magnetization is not parallel to the axis of the pipe, lateral forces occur and a decentration of the magnet happens.

The problem is studied numerically, with a T − h 3D FE formulation well‐suited for the problem. Computational results are compared with experimental results.

The physical model is given and the main force coefficients analyzed. The lateral forces and the decentration phenomenon are studied as a function of the main parameters (thickness and radius of the pipe).

The direction of magnetization is a key parameter to analyze the dynamics of a magnet motion inside a conducting pipe, when the radii of the pipe and the magnet are not so close. This analysis with a fixed direction of magnetization allows one to quantify the lateral forces and the decentration, and is a first step to understand the complete motion which includes the rotation which can be linked to the decentration.

The purpose of this paper is to introduce the dynamic hysteresis and losses of soft magnetic materials in numerical computation of high‐sensitive devices.

So as to do this, the authors propose to lump all the microscopic dynamic effects due to averaging and smoothing techniques that lead to the definition of a dynamic field as proposed by other contributions. In this paper, the method to implement the modified field diffusion process in finite element computations is investigated, explained, detailed and put to the test.

In order to take microscopic magnetization reversal processes and eddy currents that damp the field at the mesoscopic scale, the authors have been led to define a new dynamic property Λ representative of the magnetic structure and its easiness to change. It is involved in an additional term in both the magnetic behaviour law and the bulk and surface coupling formulations describing the physical problem in iron and at the borders.

This model can only be used for macroscopic pieces for which each dimension is bigger than at least four times the characteristic length of magnetic domains.

The originality of the paper comes from the need to investigate the possibility to predict iron losses and the corresponding dynamic hysteresis during the processing computation of power electrical devices such as accurate sensors and high‐sensitive actuators of earth leakage circuit breaker for example.