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Two approaches are commonly used for modelling and control of nine-phase (triple star) fault-tolerant machines with symmetrical and asymmetrical star winding configurations: The Vector Space Decomposition (VSD) and the decentralized d-q modelling. In this paper, it will be shown how the VSD approach used for machines with an Asymmetrical Star Winding Configuration (ASWC), unlike the decentralized d-q one used for machines with a Symmetrical Star Winding Configuration (SSWC), can be helpful for non-intrusive Fault Detection and Diagnosis (FDD) purposes. Supporting MATLAB/Simulink simulations are discussed.

This paper deals with the analysis of the magnetic properties degradation following an industrial impregnation process of electrical steels employed in stators of large generators. First, the impregnation process is studied directly on industrial stators to emphasize the significance of the process effect. Then, to have a controlled approach of the impregnation conditions, laminated ring cores were subjected to the same process but for different configurations. The ring cores were magnetically characterized to highlight the influence of the resin on the magnetic properties. Also, in order to distinguish the effect of the resin from potential other phenomena during the curing phase (i.e. the ageing effect), an experimental protocol is proposed: the results allow to emphasize the impact of such process on the magnetic properties.

The manufacturing processes of electrical machines may lead to significant degradation of the magnetic properties of their magnetic core (stator, rotor) performances and, as a consequence, to a decrease of their energy efficiency. While the effects of some processes (cutting, welding …) are widely discussed in the literature, this is not the case with the compaction process although it is systematically used to maintain the assembly of electrical steel sheets that compose the magnetic circuits. In addition to the conventional one, a specific compaction process exists for high-power electrical machines. After an introduction, the paper firstly deals with the two studied processes (conventional, specific). Then, an experimental mock-up to study the impact of the two configurations on the magnetic properties (iron losses, normal magnetization curve) is presented. This mock-up is the first, in the literature, that allows to study the effect of a controlled compaction mechanical stress on magnetic properties. Obtained results in both configurations highlight a magneto-mechanical effect that is not reported in the literature where these effects are commonly considered following in-plane mechanical stresses. This paper presents a magneto-mechanical model, taking into account the compaction stress effect, as well as a modelling protocol to model the effect of 3D mechanical stress on magnetic properties, which has never been done in the literature.

This paper deals with the experimental investigation of the effect of impregnation process on the normal magnetization curve and iron losses of electrical steels. To address this issue, several laminated toroidal magnetic circuits have been designed to characterize the magnetic properties with the flux metric method. The first configuration considers magnetic circuits wrapped with adhesive tape so that the dielectric resin will be deposited only on the outer surface of the magnetic circuit. In the second configuration, the magnetic circuits are unwrapped, which will allow the resin to diffuse within the inter-laminar spaces of the magnetic circuit. The obtained experimental results show significant effects on the magnetic properties in both cases. However, depending on the considered configuration, the resin diffusion also has an influence on the changes in magnetic properties.

This paper presents a novel method for demagnetization fault detection in permanent magnet synchronous machine (PMSM). Demagnetization fault is a common problem existing in PMSM which deteriorates the machine performance and can lead to serious subsequential machine damages. Unlike the most popular method based on the analysis of the machine currents for detecting this type of fault, the approach proposed in this paper analyzes the voltage signal of a non-invasive search coil by means of Hilbert Huang transform. Simulations are carried out with a two dimensional finite element analysis (FEA) for different demagnetization levels to test the capability of the proposed method to detect PM demagnetization faults.

This paper shows the influence of the shift phase angle ψ between phase currents and back-electromotive forces on magnetic radial forces and torque ripple for a specific low power permanent magnet synchronous machine. This influence is firstly demonstrated through analytical development considering only the first harmonic values. Then, magnetic pressure harmonics versus space and frequency as well as torque ripple are evaluated on the studied motor for different angles using finite element approach. The aim is to establish a good compromise between consumed current, torque and radial force harmonics at the origin of the electromagnetic noise. Experimental measurements with a sensorless field-oriented control are detailed.

Purpose This paper deals with the study of the influence of the phase shift between currents and back-electromotive forces (back-EMF) on torque ripple and radial magnetic forces for a low power synchronous machine supplied with 120 degrees square-wave currents. This paper aims to establish a good compromise between efficiency, harmonics of torque and harmonics of radial forces at the origin of the electromagnetic noise. Design/methodology/approach Based on a finite element approach, torque and magnetic pressure harmonics versus space and frequency are evaluated for different angle values. The evolutions of the different harmonics against the load angle are analyzed and compared to those of experimental measurements. Findings Depending on the load torque, field-weakening or field-boosting can be used to reduce current harmonics contributing the most to the radial magnetic forces responsible for the noise. Besides, a compromise can be found to avoid deteriorating too much the performances of the machine, thus being suitable with an industrial application. Research limitations/implications This study concerns low power permanent magnet synchronous machines with concentrated windings and driven with a trapezoidal control, while having sinusoidal back-EMF. Originality/value The use of a simple mean and suitable with a large-scale manufacturing industry to reduce the identified electromagnetic-borne noise of a specific electric drive makes the originality.

The manufacturing processes of electrical machines may lead to significant degradation of magnetic core properties and therefore of the machine performance. Laminations are usually stacked and pressed which affects the magnetic properties and the iron losses. However, the influence of this step must be still investigated when large generators are considered. Indeed, in that case, the stator and rotor stacking process consists in assembling several stacks of electrical steel sheets separated by airvents. The surface of the airvent spacers represents about ten percent of the lamination surface of the magnetic circuit, implying, during the compaction process, an inhomogeneous stress distribution with significant local stresses. The present work deals with the experimental characterization of a lamination stack, including airvents, under compressive stress in the thickness direction. A mock-up has been designed and built-up to study magnetic properties of lamination stacks under pressing conditions corresponding to the industrial process.

This paper deals with the calculation of iron losses in a turgenerator using a magnetodynamic Finite Element (F.E.) Analysis accounting for the eddy currents in the damper bars. Two iron loss models, based on the Berttoti’s decomposition approach, are compared in the post-processing step of a F.E. calculation. The numerical model of the studied system is validated by comparing the calculation and the experiment for no-load conditions.

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, a methodology using the 3-D finite-element (FE) modeling approach and a posteriori loss calculation is presented for the estimation of the stray load losses. The case of a cage induction motor is investigated, and results are compared with the experiment. The simulation is performed at different load conditions using a 3-D FE model with external circuit coupling.

The stray load losses (SLLs) in electrical machines represent a non-negligible contribution of the total losses and a key point for an accurate evaluation of the energy efficiency of considered device. In this paper, one aspect of these SLLs, the end-region leakage fluxes and losses, is investigated and considered for the case of a high-power cage induction motor. The study is performed at locked rotor, no-load, and rated load conditions using a 3-D finite-element modeling approach. The influence of the leakage flux on the end-region conductive parts of the motor is analyzed together with the eddy current loss calculation. Finally, the SLLs are calculated and compared with the experimental measurements based on the IEEE standard 112-method B test.

NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the eddy current loss of PMs, but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are then compared with those of a 3D FE model.

Permanent magnets are commonly used in electromechanical energy conversion devices, especially in permanent magnet synchronous machines (PMSM). When designing such devices, it is necessary to take account for the operating conditions of the permanent magnets. Ideally, the operating point of the magnet lies on a linear reversible demagnetization characteristic. Nevertheless, the operating conditions (temperature, demagnetization field, etc.) may have great influence on the magnetic characteristic that becomes strongly nonlinear and may lead to magnetization loss in the magnet. Consequently, the impact is also observed on the electrical machine performances. This paper presents a nonlinear model accounting for magnetization loss of permanent magnets which magnetic characteristic presents knee points in the demagnetization curve. The presented model is applied to analyze the local magnetization loss in magnets of a PMSM.

This paper deals with a stochastic approach to model the pull-in voltage in a microelectromechanical system (MEMS) beam structure. Two nonintrusive stochastic techniques are used: a sampling method, based on Monte-Carlo simulations and a polynomial chaos expansion (PCE) approach. The deterministic model solves an electro-mechanical problem using a coupled 2-D finite element (FE) electrostatic and Euler–Bernoulli beam equation mechanical model. The influence on the pull-in voltage of three parameters subjected to uncertainty (material properties and shape) was investigated. Also, the advantage of the PCE method, compared to Monte-Carlo sampling method, was emphasized.

The perturbation method is a simple way to study local details while avoiding a fine mesh of the whole system. In this paper, we present the influence of the extracted region size, i.e. the region including the perturbation, when performing iterative calculations with the perturbation technique. This influence is illustrated using a simple example.

This paper deals with the study of static and dynamic rotor eccentricities of a synchronous generator using 3D FEM. First, both eccentricity cases are introduced as well as the used approach. Then the models of the structure, based on the magnetic scalar potential formulation and on the magnetic vector potential formulation, are presented. Two eccentricity modeling methods are introduced, the 2D eccentricity and the 3D eccentricity. Results obtained for magnetostatic and magnetodynamic cases related to both defects and their combination are presented and discussed.

Closed form expressions for the computation of the pull-in voltage, can provide fast results within reliable accuracy, except when treating cases of extreme fringing fields. Finite Element based models come handy when high accuracy is needed. In the first model presented in this paper the FEM is used to solve the electrostatic problem, while the mechanical problem is solved using a simplified Euler-Bernoulli beam equation. The second model is a pure FEM model coupling the electrostatic and mechanical problems iteratively through the electrical force. Results for both scalar potential and vector potential formulations for the FEM models are presented.

Purpose – The purpose of this paper is to present an analysis of the force ripples of an open slot permanent magnet linear synchronous motor (PMLSM). A calculation procedure using 2D finite elements method (2D-FEM) is then evaluated with experimentations. Design/methodology/approach – First, the studied PMLSM and its main features are introduced. Then, the 2D-FEM model used to study the motor is presented. The methods used to calculate the force and the meshing procedures are also highlighted. The calculated no-load force is compared to measurements. Lastly, the validated model is used to study the influence of the current magnitude on the force ripples at load. Findings – In addition to the no-load case, the influence of the current magnitude on these forces is presented. Originality/value – The paper is orientated with a sound industrial background. For that reason, the impact of the current saturation on the thrust generation is presented via the evolution of the thrust coefficient, which is the force to the RMS currents ratio.

In an advanced micro-lithographic system, it is of critical importance that components are resiliently isolated from external vibrations. In this paper, a passive/active electromagnetic solution is discussed, where passive permanent magnets (PM) provide the gravity compensation and active electromagnets accurate positioning. Focus is on PM modelling, as an accurate model is inevitable to achieve the high accuracy required for such application. This paper describes a study on interaction force along three degrees of freedom (DoF), between permanent magnets (PMs) having an unaligned magnetization direction for use in a PM-based suspension application. Feasibility of finite element modeling (FEM) and analytical modelling for such structures is discussed, implemented and verified with experimental measurements.

In this paper, we propose to study an electromagnetic actuator which involves linear and /or rotary movements. The studied device is constituted of permanent magnets, iron teethed armature and concentrated coils with a simplified design. The aim of this paper is to study the main electromagnetic features of the actuator using 3D finite element method. First, the actuator is described and the design choices are given and discussed. Then, the electric and magnetic behaviors (fluxes, forces,…) are studied thanks to 3D-FEM analyses. The formulation used is introduced. Finally, results are given and compared to measurements.

We describe in this paper the design of a permanent magnet actuator for linear and rotary movement. The actuator can make linear and rotary movements and special attention has been placed on the simplicity and the swiftness behavior. At first, we compare the different approaches to perform a linked movement and a structure is adopted. Then, we detail the adopted magnetic conversion through a rotary machine and a linear actuator. In a last part, the studied actuator is presented and results concerning the flux linkages and forces are given using 3D finite element simulations.

Nowadays, the electromagnetic actuators for industrial processes have to present very specific features which can not always be obtained by classical machines. Hence, to reach the wanted features, one has to design the actuator and to quantify its performance with a good accuracy and reasonable computation time. The purpose of this paper is to present the design and the study of a linear actuator. First, we present the design of the chosen actuator structure. The second part is devoted to describe the approaches used (permeance network model and the 3D Finite element model) to study the behaviour of the actuator. Lastly, we give the results of the study, obtained by both models, and we compare them to experimental data obtained from the prototype build up.

An accurate thrust control of permanent magnet linear synchronous motors (PMLSM) is more efficient with a fine knowledge of the harmonics value of the electromotive force (EMF). This is often difficult to obtain experimentally for a PMLSM. As a consequence, this paper deals with the study of the non-sinusoidal EMF of a PMLSM using the 3D Finite-Element Method (FEM). Two potential formulations are used to consider several cases. Afterwards, for the same accuracy, the computation times are examined. The results of the FEM are compared to those given by the measurements from a test bench composed of a Siemens LIMES400/120 linear motor and a dSPACE DS1005 real-time controller board. Finally, the advantages and the limitations of the FE Analysis will be discussed.

The control of a wind energy conversion system can be decomposed in two parts: a local control depending on the power structure and a global control (strategy) deduced from global considerations. The local part ensures an efficient energy management of each component of the system. The local control structure can be deduced from the Energetic Macroscopic Representation, which is a graphical description of the system according to action and reaction principle. Using inversion rules, the deduced control structure is composed of a maximum of control operations and measurements. The global control part is independent of the power structure. This strategy part leads to achieve power objectives (active and reactive power targets) and system constraints (machine efficiency and DC bus limitation). Several strategies can be defined for the same system. These control decomposition is applied to a wind generation system composed of a permanent magnet synchronous generator and two three-phase converters. Simulation results are provided for a 600 kW wind energy conversion system.

For some specific industrial applications, such as large generators, once the magnetic circuits are built and wound, they are usually impregnated with a dielectric resin, which is polymerized under heat treatment, to ensure insulation, thermal and mechanical properties. This talk is about the experimental study of the effect of such impregnation process on the magnetic properties of electrical steels used for the manufacture large generator stators.

In this work, we propose to characterize and analyze the phenomena involved by an industrial impregnation process that degrades the magnetic properties (B-H curve, iron losses) of electrical steels. Two main aspects are considered: the thermal effect as well as the dielectric resin deposition and diffusion within the magnetic circuit.

This paper presents a combined experimental/numerical approach to identify the degradation profile of the magnetic characteristics regarding the distance from the cut edge of punched electrical steels. Using a dedicated magnetic measurement device and mechanical hardness measurements, the impacted cutting-edge (I.C-E) distance has been experimentally identified. In association with a magneto-plastic model, the numerical model allows to determine the I.C-E distance and its associated degradation profile by an inverse optimization method.

To design and study an electrical machine, Finite Element Model (FEM) is nowadays the most accurate approach as it takes into account different phenomenon. However, it is also time-consuming which does not always make it suitable for an optimization process. Analytical model can then be used but it has to be as accurate as possible in order to obtain valid and relevant results. In case of squirrel cage induction machines, several analytical models have been proposed under different simplifying hypothesis [1]–[3] The well adapted one is the approach involving winding function to determine the armature Magneto Motive Forces (MMF) along with the air gap permeance. These two quantities can be expressed in a relatively accurate way [4]. The problem then remains in taking into account the rotor part in order to determine the currents which circulate in the bars of the squirrel cage. Indeed, in addition to the well estimate of the magnetic flux through the rotor surfaces, the determining of the elements of the equivalent electrical circuit which makes it possible to precisely calculate the currents of the bars in the most accurate way is required. In the present paper, an analytical model of the squirrel cage based on an equivalent electrical circuit along with the approach to accurately identify its parameters is proposed. This model that enables to determine the rotor bar currents can be generalized to any structure and thus be used either for design or optimization purposes. Results obtained in the case of an induction machine prototype are compared to the ones given by FEM.

Magneto Motive Force is an important quantity to analyze electrical machine performances. Indeed, the latter is directly linked to that of the air gap magnetic flux density and thus to the torque ripples, vibration and then noise. This paper proposes to reduce the MMF harmonic content by means of optimization process using mono-objective or multi-objective algorithms with discrete and continuous variables. For this aim, optimization algorithm is coupled with an analytical tool which enables calculating quickly the MMF harmonic content from winding parameters. A winding optimization of three different windings with the same number of pole pairs is proposed to show the suitability of this process.

This paper deals with the study of the influence of the phase shift between currents and back-electromotive forces on torque ripple and radial magnetic forces for a low power synchronous machine supplied with 120 degrees square-wave currents. Based on a finite element approach, torque and magnetic pressure harmonics versus space and frequency are evaluated for different angle values. The aim is to establish a good compromise between efficiency, harmonics of torque and harmonics of radial forces at the origin of the electromagnetic noise. The evolutions of the different harmonics against the load angle are analyzed and compared to those of experimental measurements.

Study of the impact of stator MMF from different winding distributions using FEM can be tedious when taking into account the stator slots as it introduces mesh constraint and reluctance variation of the air gap. To avoid this fact, a current sheet spread all around the inner stator surface is used. In the proposed approach, the MMF is modelled by the equivalent current sheet of the real stator MMF in the air gap. This current sheet is coupled with an analytical tool that allows obtaining the spatio-temporal stator MMF of any winding considered. Compared to an analytical model, the proposed approach enables taking into account the non linear behaviour of magnetic material in the yoke and thus testing different combinations of stator windings in more realistic conditions.

This paper shows the impact of the shift phase angle ψ between phase currents and back-electromotive forces (back-EMFs) on torque and radial forces for a low power synchronous machine (20 W). Pressure harmonics versus space and frequency on our motor and torque are evaluated with different angles with finite element approach. The aim is to establish a good compromise between consumed current, harmonics of torque and harmonics of radial forces linked to the electromagnetic noise for two strategies: maximum torque per ampere (MTPA) control and field weakening (FW) control. The evolution of each harmonic versus ψ are compared for both strategies. Experimental measurements in sinusoidal case are detailed.

Permanent magnet brushed DC motors are used in several applications such as home automation or automotive industry. This is mainly due to their lightweight, low cost and compact structure. Thus, the importance to study the sources of noise and vibration in these motors, which is often complicated and can be attributed to many factors. In this paper, the cogging torque and electromagnetic forces are studied in the case of a small permanent magnet brushed DC motor with 2 poles and 3 slots. Addition of dummy slots on the rotor side is described with its effect on the evolution of both aspects. The aim of this study is to give the quantitative effect about torque ripple and radial forces for each harmonic in relation with these dummy slots.

This paper presents a novel method for demagnetization fault detection of per-manent magnet synchronous machine (PMSM). Demagnetization fault is a common problem existing in PMSM which deteriorates the machine performance and can lead to serious secondary machine damages. Unlike the most popular method for detecting this fault which is based on the analysis of the machine current, the approach proposed in this paper analyses the voltage signal of a non-invasive search coil by means of Hilbert Huang transform. Simulations are carried out with a two dimensional finite element anal-ysis (FEA) for different demagnetization levels to verify the proposed method.

The magneto motive force is an important physical quantity for electrical machines. Indeed its harmonic content leads to that of the air gap flux density. This paper presents an optimisation of the winding distribution for three phase fractional slot concentrated winding (FSCW) and distributed winding (DW) in order to reduce the magneto motive force harmonic content. This have an important effect on torque ripples, vibration and then noise. The optimization will be done on continue and discrete variables linked to the winding distribution.

Magneto motive force is a key quantity of the energy conversion in the electrical machines. Its harmonic content is important as it leads to the one of the magnetic flux density in the air gap. To analyze it, a first step consists to study the winding function. Many tools already exist to tackle this point but generally they use some methods like Star of slots or matrix representation and the harmonic content is obtained by a Fast Fourier Transform of the total winding function. In the present paper, we propose to build up the winding function using elementary patterns whose harmonic contents are used to reach the one of the whole function using a geometrical construction. This approach is quite fast and allows easy analyzing in order to reduce or cancel a magnetic harmonic.

The aim of this paper concerns the design with these targets for low power motors that offer a good compromise in terms of performance: speed, torque, current, and noise linked to the radial forces. Different low power machines and topologies are studied with the same constraints in term of volume for the same value of the torque. The study is carried out on a PMSM with surface permanent magnet ‘SPM’ and with insert permanent magnet ‘IPM’. In order to reduce the cost, a synchronous reluctance machine ‘SynRM’ is also designed and studied. 2D and 3D Finite Element modeling are used to compare the performance of the three different topologies. In addition, the best solutions are realized and tested.

Shaft voltage is present in all electrical machines and can be useful as a diagnosis variable but first, it is important to quantify the effect of some defects. 2D numerical models have already been used to tackle this point. However, 3D effects due to end windings can have a significant influence on this voltage. This paper deals with the study of a turbo-generator using a 3D finite element model in order to investigate this task.

This paper studies different low power machines and topologies with the same constraints in term of volume for the same value of the torque. The aim of this paper concerns the design with these targets for low power motors that offer a good compromise in terms of performance: speed, torque, current, and noise linked to the radial forces. The study is carried out on a PMSM with surface permanent magnet ‘SPM’ and with insert permanent magnet ‘IPM’. In order to reduce the cost, a synchronous reluctance machine ‘SynRM’ is also designed and studied. 2D and 3D Finite Element modeling are used to compare the performance of the three different topologies.

In large turbo-generators, the analysis of the shaft voltage can be useful to diagnose some defects such as eccentricities or rotor short circuit. To do that, the first step is to quantify the inherent effect of each defect on that voltage. This paper deals with the study of a simplified synchronous generator with a smooth slotless stator using a numerical model in order to well understand the effect of each defect.

Abstract—The presented paper proposes a topology optimisation methodology based on the density-based method SIMP, and applied to a numerical example to validate the former. The approach and methodology are detailed, and the results for a 3D basic electromagnetic example are presented. The non-linear B(H) curve is also taken into account. Index Terms—gradient-based algorithm, relaxation of variables, SIMP density method, weighted objective sum

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, a methodology using the 3-D finite element (FE) modeling approach and a posteriori loss calculation is presented for the estimation of the stray load losses. The case of a cage induction motor is investigated and results are compared with the experiment. The simulation is performed at different load conditions using a 3-D FE model with external circuit coupling.

Abstract. This paper presents different approaches while using the SIMP density-based method for the Topology Optimisation (TO) of a 3D electromagnetic device. The methodology used for TO is also detailed in this paper. The initial model and the formulation of the problem are presented, and the results for two approaches are analysed. A Finite Element calculation code is coupled with a gradient-based algorithm to numerically execute the proposed methodology for TO. Keywords: 3D Finite Element Model, gradient-based fmincon SQP algorithm, SIMP density-based method, Topology Optimisation

In the case of high power synchronous machines, shaft voltage can induce high currents yielding to bearing damages but it can also constitutes a variable to be used to diagnosis some machine defects. Therefore, it is important to well model the phenomenon in order to use it in further diagnosis tool.

The goal of this paper is to identify rotor inter-turn short-circuits of an alternator. The detection method is based on the analysis of a ux probe signal located in the air gap of the machine. Previous works have shown that pattern recognition can be applied to detect such a fault by using the experimental data as prototypes. A new method is developed here by considering a learning step based on simulation. Therefore the machine is modeled and validated. A feature selection is made by considering feature correlation and disparity. Finally, k nearest neighbors is used to classied experimental test data.

Electromagnetic losses in permanent magnet synchronous motors (PMSM) occur in the laminated core as well as in the permanent magnets (PM). These losses can lead to an overheating of the PMs that are subject to magnetization loss. Due to the difficulty of distinguishing experimentally the iron losses in the laminations from the eddy current losses in the PM, it is necessary to resort to the simulation. In this work, the losses of a PMSM, fed by a PWM inverter, are investigated using the 3-D FEM. The PWM measured signal is imposed, using a linear interpolation and respecting the harmonic content, as an input of the simulation.

This paper presents a methodology to optimise the topology of a 3D electromagnetic model to maximise Energy while constraining the Material Quantity. Variants of the material distribution method SIMP (Solid Isotropic Material with Penalisation) are discussed to enhance convergence of variables. The aim is to improve the results by analysing the behaviour of the design variables w.r.t the objectives. This allows correct parameter tweaking and finding the best variant for the SIMP Method respective to our methodology. This would help reduce the time consumed to find the best solution and therefore enhance the accuracy of the results.

The goal of this paper is to identify the real parameter set of a given machine. The identification method is based on data assimilation coupled with a FEM model. Data assimilation method is an optimization approach that limit the space of candidate parameter sets by centering it to the ideal machine. An application to an electrical machine is presented based on the analysis of flux probe signals.

The stray load losses represent a non-negligible contribution to the total losses in electrical machines. This paper investigates a contribution to these losses in the case of a non-skewed squirrel cage induction motor, namely the zig-zag flux. The study is performed at no-load, locked-rotor and load conditions for an induction machine with different rotor slot openings, using a time stepping 3-D finite element modeling approach. The discrete Fourier transform is used to analyze the magnetic flux density waveforms in the air gap and deduce the main harmonics related to the zig-zag flux. The influence of the rotor slot opening on the zig-zag flux and core losses, in both rotor and stator, are discussed.

Vibration and acoustic noise can constitute a serious problem for Switched Reluctance Motors (SRMs). They are mainly caused by the deformation of the stator lamination stack due to its magnetic attraction to the rotor. This paper presents a 2D multi-physic methodology which permits to predict electromagnetic acoustic noise generated by SRMs, since the early design phase. In order to achieve the best compromise between accuracy and computational time, a hybrid methodology was adopted. It is based on a Finite Element (FE) magnetic model to take into account magnetic nonlinearities, especially for SRMs which are usually highly saturated. The vibration and acoustic models are based on analytic approaches and are integrated in an in-house tool we developed: GRIMM (Generic Ring Model for Magnetic Noise). This tool has been validated by a full FE approach for an 8/6 SRM at each step and good agreements are obtained. Its accuracy was improved by taking into account the stator teeth effect in terms of mass correction and by means of quasi-axisymmetry hypothesis.

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, one aspect of these stray load losses, the end-region leakage fluxes and losses, is investigated for the case of a high power cage induction motor. The study is performed at locked rotor condition using a 3-D finite element (FE) modeling approach. The influence of the leakage flux on the end-region conductive parts of the motor is analyzed together with the eddy current loss calculation.

NdFeB permanent magnets (PM) are widely used in high performance electrical machines but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. Finite Element (FE) method is generally used to quantify the eddy current loss of PM but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are compared with those of a 3D FE model.

The main advantages of the Switched Reluctance Motor (SRM) are its robust construction and its low cost which makes this technology an attractive solution for traction applications. However, one of its major drawbacks is the high mechanical vibrations and acoustic noise. These vibrations and acoustic noise are mainly caused by the deformation of the stator lamination stack due to its magnetic attraction to the rotor. The aim of this study is to build a complete coupled multi-physic tool allowing the prediction of electromagnetic acoustic noise in an 8/6 SRM. The goal of such a tool is to be integrated in an optimization process. This tool is based on 2D electromagnetic, vibration and acoustic models which are calculated through analytical approaches. The vibro-acoustic analytical results are compared to those of a FE approach and good agreements are obtained.

This paper presents a study on iron loss estimation for a solid rotor induction motor fed by Pulse Width Modulated (PWM) supply. The iron losses are often determined using an a posteriori method that can lead to more or less important deviations, compared with measurements, depending on the used models and implementation techniques. The methodology proposed here consists in computing the iron loss with an analytical method implemented in a post-processing of a 2D finite-element analysis. Different implementation techniques are used in order to investigate the impact of the model on the total iron loss.

NdFeB permanent magnets are widely used in electromechanical energy conversion devices, especially in high performance electrical machines. When designing such devices, it is necessary to take account of the operating conditions of the permanent magnets. Ideally, the operating point of the magnet lies on a linear reversible demagnetization characteristic. Nevertheless, the operating conditions (temperature, demagnetization field …) may have great influence on the magnetic characteristic that becomes strongly non-linear and lead to irreversible magnetization loss. To study such effect, the Finite Element (FE) method can be used in order to describe with accuracy the local demagnetization loss of a permanent magnet (PM). Therefore, the present work deals with the nonlinear modeling of a PM implemented in a 3D FE model that takes into account the partial demagnetization effects with temperature dependencies.

Vibration and acoustic noise can constitute a serious problem in electric machines. They are mainly caused by the deformation of the stator lamination stack due to its magnetic attraction to the rotor. This paper presents a 2D multi-physic tool which permits to predict electromagnetic acoustic noise generated by electric motors, since the early design phase. This tool is based on 2D magnetic, vibration and acoustic models and the final goal is to find the best compromise between accuracy and calculation time. The magnetic model is based on the Finite Element (FE) method in order to take into account nonlinearities, especially for SRMs which are usually highly saturated. The vibration and acoustic models are calculated through analytic approaches. The analytical results are then compared to those of a full FE approach for an 8/6 SRM and good agreements are obtained.

The goal of this paper consists in applying pattern recognition methods to turbo-generators. Previous works have shown that a monitor, thanks to pattern recognition, is practical on asynchronous machines. This procedure has rarely taken advantage of these methods for turbogenerator. The statistical model has been obtained from harmonics extracted from flux probes and from stator current and voltage. For this purpose, the main way is to build a learning matrix to predict the functional state of a new measurement. Finally, three classifiers have been compared: k Nearest Neighbors, Linear Discriminant Analysis and Support Vector Machines. The best classification result is obtained by Linear Discriminant Analysis combined with Factorial Discriminant Analysis achieving a score of 84.6%.

This communication addresses the modelling of the parameter known as the pull-in voltage in electrostatic MEMS (Micro Electro Mechanical System). As this parameter is sensitive to the physical parameters of the MEMS device, a stochastic modelling approach may be required. Two non-intrusive stochastic techniques are used: a sampling method based on Monte-Carlo simulations and a Polynomial Chaos Expansion (PCE) approach. The electro-mechanical problem is solved using the coupling between a 2D Finite Element (2D-FE) electrostatic model and the Euler-Bernoulli beam equation for the mechanical model. The influence on the pull-in voltage of three parameters subjected to uncertainty (material property and geometry) is investigated.

This paper investigates the stochastic post-processing calculation of iron losses. Twenty eight slinky stator samples are investigated in term of iron losses variability, and stochastic model is then developed to take account of this variability. The Multivariate Gaussian distribution (MG) of the iron losses parameters is thereafter used for stochastic post-processing calculation of the density of iron losses of a PMSM, with Monte Carlo simulation method. This approach allows one to take in consideration the magnetic core variability from the iron loss point of view, for the design of electrical machine.

Pulse width modulated (PWM) inverters are widely used to feed induction motors for variable speed applications. The use of PWM power supplies induces additional magnetic losses in the magnetic circuit of the electrical machine. In this paper a novel analytical approach is presented to account for these losses. The methodology proposed here consists in identifying the analytical method with a static Preisach hysteresis model. The Preisach model was validated by comparing it with measurements obtained from an Epstein frame. Then, the results obtained with this approach were compared with a basic analytical method that is widely used.

Permanent magnets (PM) are widely used in various types of electrical machines and devices. However, they can be subjected to magnetization loss depending on the operating conditions. Therefore, when modeling devices involving PM, it can be useful to use an accurate description of the magnetic behavior law of the PM in order to predict any demagnetization that will impact their performances. Usually, the Finite Elements (FE) approach is used in order to describe with accuracy the magnetic operational conditions of the PM devices. These conditions depend of the magnet temperature and also of the spatial and temporal harmonics of the magnetic field developed in the PM [1]. The magnetic behavior law of PM is generally assumed to be linear. The real demagnetization curve can also be taken into account by implementing a non-linear behavior law. Nevertheless, the magnetization loss is not always taken into account, especially when the operating point of the PM reaches the knee point. Therefore, in this communication, a model describing the modification of the behavior law of a PM is described in this condition. The model is implemented in a FE calculation code with an example of application.

Iron losses during electromechanical energy conversion devices are crucial in electrical machine design. They are often determined using an a posteriori method that can lead to more or less important deviations with regard to the experiment. These deviations can be explained both by the lack of accuracy of the iron loss model but also by the numerical modeling procedure and hypothesis. This paper investigates the impact of the numerical error on the evaluation of iron losses in an electrical machine stator.

This paper deals with the study of the effects of the eddy current induced in the damper bars of a synchronous machine at steady state. A non-salient pole synchronous machine, with damper bars, is modelled in magnetostatic and magnetodynamic cases taking into account the end rings. The time variation of the no load back emf is calculated in both cases and the results are compared to measurements to highlight the effects of the induced currents.

When ferromagnetic materials are subject to a time varying magnetic flux, energy dissipation, known as iron loss, occurs within the material. These losses are often determined using an a posteriori method that can lead to more or less important deviations depending on the used method. In electrical machines, one has to take into account the vectorial behavior of the magnetic field that can lead to additional losses. In this work, two iron loss calculation approaches, implemented in a post processing of a 3D finite-element analysis, are used in order to investigate the impact of rotational losses in a three-phase transformer.

This paper deals with the study of rotor turbogenerator eccentricities using an analytical approach and FEM. First, we present the cases of eccentricities and the method, based on the measure of the flux density in the air-gap, used to detect the faults. Both models, the analytical approach and the numerical one are then introduced. Using these models, static, dynamic and combined eccentricities are studied at no load. The results obtained by both approaches are compared and the limits of the analytical model are underlined relatively to the effect of the non linearity of the magnetic material characteristic and the induced eddy currents.

This paper deals with the study of interturn short circuits in rotor windings of a synchronous generator using FEM. Results obtained for magnetostatic and magnetodynamic cases are presented and discussed.

The paper deals with the study of static and dynamic rotor eccentricities of a synchronous generator using 3D FEM. First, both eccentricity cases are introduced as well as the used approach. Then, the model of the structure, based on the vector potential formulation is presented. Results obtained for magnetostatic case related to both defects and their combination are presented and discussed. The saturation effect is highlighted.

The perturbation method is a simple way to study local details while avoiding a fine mesh of the whole system. In this paper, we present the influence of the extracted region size, i.e. the region including the perturbation, when performing iterative calculations with the perturbation technique. This influence is illustrated using a simple example.

Specific electromagnetic actuators are now widely used. Several designs exist and depend on the aimed application. The goal of this paper is to present a general overview of the integrated linear and rotary actuators (called also Z-Theta actuators). First, the different ways to achieve this movement are given. Then, we present the design of the actuators actually studied or constructed. At last, a summary table of the actuators is drawn up.

This paper focuses on the design of a new type of linear electromagnetic MEMS. High thrust density is generated using the current/magnet/iron interaction. The proposed innovation is based on flexible beams, serving as a guidance system and as a closing magnetic circuit. The fabrication process is defined and 2D-Finite Element Analysis is performed in order to maximize the thrust generation under low current values and small actuator sizes.

In this paper, movement strategy, using the overlapping method, is studied. Non-conforming tetrahedral meshes and planar displacements are considered. The first part of this paper is devoted to the presentation of the FEM formulation. In the second part, the overlapping method is described in the case of planar movements. At last, results are given and discussed.

This paper presents an analysis of the force ripples of a permanent magnet linear synchronous motor (PMLSM) with regards to the current magnitude. This approach takes into account the influence of the currents in the generation of the force ripples. A 2D-Finite Element Analysis is developed, and experimental results on a test bench validate the proposed model.

The analysis of micro-electro-mechanical systems (MEMS) requires to take into account both electric and mechanical phenomena. An iterative FEM approach, which involves the computation of the electrostatic field and the displacement of the moving part, is presented. The maximum displacement allows computing the pull-in voltage.

Recently, magnetic gearboxes know a real interest and have been the subject of many studies due to their high performances. However, their principle is often issue from the mechanical gearbox one and then they do not offer any degree of freedom. In this paper, we propose a magnetic gearbox constituted of two electromagnetic structures. This introduces two degrees of freedom and then the system can also insure clutch operating. First, the operating of the system is described. Then, its behavior is studied using a numerical model based on 3DFEM. Different results given by 3D analysis are presented.

Due to industrial needs, small stroke actuators present a growing interest. Generally, high acceleration, robustness and low manufacturing costs are frequently required. Today, improvements in the magnetic material as rare earth magnets or iron powder permit to design very compact actuators. To reach high performances, the actuator has to be controlled. This can be achieved using the last control capabilities (dsp, fpga...).However, this often needs sensors which increase the costs. In this paper, we deal with the simulation of the control of a PM linear small stroke actuator with non mechanical sensors. First, we present the actuator features. Then we introduce the simulation model based on the reluctance network model. To reach the information related to the position of the moving part, we use Hall effect sensors. In a third part, we show the placements of the sensors. Lastly, we introduce the control strategy and give some simulation results.

Analytical models of Surface Mounted Permanent Magnet Linear Synchronous Motors are generally presented with constant inductances. However, the impact of powerful rare-earth PMs in the saturation phenomena cannot be neglected anymore. In this paper, a new non-linear model of PMLSM inductances is suggested. This model is defined as a function of the current value as well as of the magnet position. So, an analytical study, a finite-element analysis and experimental results are presented and confronted.

Nowadays, numerical approaches are widely used to model electrical machines. Among them, the 2D-finite-element method (2D-FEM) is the most frequently encountered to study the behaviour of electromagnetic devices. Indeed, it takes into account both the geometry of the system and the non linearity ofthe magnetic material. Then, it offers accurate results with regard to the real system. To obtain fast optimizations of electric machine designs, a low number of mesh elements is required in order to limit the computation time. However, this generally undermines the accuracy of the results. In the case of global electrical characteristics such as fluxes or electromotive forces, the quality of the mesh does not affect the result greatly. This is not the case of the no-load torque or force. Indeed, accurate calculations are highly dependent on the method used to perform them and on the mesh quality of the modelled part of the device. Hence, one has to take care of these parameters to reach useful results, especially given that the no-load torque or force are generally very difficult to obtain from measurements. These difficulties are increased in the case of the permanent magnet linear synchronous machines (PMLSM) as the no load force is composed of two parts, the cogging and the extremity ones. In this paper, in order to accurately calculate the no-load force using the FEM, we propose a meshing procedure of a PMLSM and a comparison of force formulations. In the first part, we introduce the formulations that are generally used to calculate the forces in the FEM codes. The problem of the force accuracy calculation induced by the meshing size is considered. The second part of the paper is devoted to the mesh design of a PMLSM. We define an elementary part of the PMLSM to be modelled and the main geometrical characteristics are explained. The results obtained from different meshes are analyzed. Some comparisons are carried out on the effectiveness of force formulations, the accuracy of the results and the time calculations. In the last part, the simulation results are compared to those obtained on an experimental bench

Linear machines are more and more studied and used in industry applications. Nowadays, such machines are available with synchronous, asynchronous and variable reluctance electromechanical conversion. Following the aimed application, Permanent Magnet Linear Synchronous Motors (ironcore PMLSM) are widely used in applications which need very high performances in terms of dynamics, high speed and accurate positioning. This is especially due to the utilisation of rare earth permanent magnets. Hence, these structures have a high power to weight ratio, which makes them attractive in the case of embarked applications. However, as for their rotary counterparts, the use of permanent magnets, and even more rare earth ones, induces drawbacks. Indeed, they suffer from cogging forces due to the presence of slots in the primary. Furthermore, the extremities of the short primary induce end-effect forces. Both forces compose the detent force and lead to vibrations and issues in achieving efficient control at low speeds without specific compensations. Today, the finite-element method (FEM) is widely used to design electrical machines. This numerical approach takes account of the real geometry and the non linearity of the magnetic material, which leads to accurate results with regard to the real system. It can be helpful to shape the no-load PMSLM forces and then to constitute a prevailing tool to optimize such PMSLM design. The studies of the cogging force for electrical machines (rotary and linear) are numerous. But the investigations on the study and the minimization of the end-effect forces are limited. Besides, their physical origin is not well known and the solutions given to limit it are often issued from experimental tests. In this paper, we propose to use the finite-element method to study the cogging forces and the end-effect forces that compose the no-load detent forces. Influent geometrical parameters of a particular PMLSM are considered. Hence, once the geometrical parameters inducing the end-effect force are well known, it would be easier to adapt them to reduce it. In the first part, we present the studied PMLSM and introduce the geometries utilised to reach both forces. A special meshing technique is introduced. The second part is devoted to analyse the no-load forces. As a consequence, the ripple force due only to the reluctance variation of the air-gap is studied first. Then, identically, we analyse the force introduced by the extremities. These results are compared to measurements on an experimental bench. In the last part, the influence of geometrical variables on both forces is presented and discussed.

Permanent magnet actuators, widely used, often suffer from torque or force ripples. In this paper, we intend to reduce the cogging force of a PM linear actuator using two approaches. The first one consists on an optimisation of the teeth and magnet sizes. The second deals with the use of a supplementary steel piece in order create an opposite cogging force. The first calculations are achieved using 2D-FEM. Then 3D-FEM is used to validate the results.

The electromagnetic actuators for industrial processes have nowadays to present very specific features. To lead to a prototype and to study it with high accuracy, we use today partially or completely numerical methods. The purpose of this paper is to present the design and the study of a linear actuator. First, we present the structure of the actuator and its characteristics. The second part is devoted to describe the numerical approach. Lastly, we give the main results of the study and compare them to experimental data obtained from a prototype.

In the field of numerical modeling, applications with complex displacements are more and more met. The present paper deals with a procedure which permits to take into account two movements in the finite element method. Using the locked step method, it is possible perform both X-Y and X-q displacements. The procedure developed is explained and a 3D simple example is studied, both in magnetostatic and magnetodynamic, to show the validity of the proposed method.

Specific actuators are now widely used. The design and study of such a converter must be carried out using specific models. This paper deals with the study of a permanent magnet planar actuator with Multiple Degrees of Freedom (MdoF). A 3D permeance network model is used to design the actuator and study its performance. The 3D-FEM is also used to investigate more accurately the prototype behavior. A prototype of the actuator has been built. Results, given by both models are shown and compared with those obtained experimentally.

In the case of permanent magnet linear synchronous motors (PMLSM), knowledge of the electromotive force (emf) is necessary to achieve accurate control. However, it is often difficult to obtain it experimentally. As a consequence, this paper deals with the study of the non-sinusoidal emf of a PMLSM using the Finite-Element Method (FEM). Two potential formulations are used to consider several cases. Then, for the same accuracy, the computation times are compared. The results of the FEM are compared to those given by the measurements from a test bench composed of a Siemens LIMES400/120 linear motor and of a dSPACE DS1005 real-time controller board. Finally, the effectiveness and the limits of the FE Analysis will be discussed.

Specific actuators are now widely used. The design and study of such a converter must be carried out using specific models. This paper deals with the study of a permanent magnet planar actuator with Multiple Degrees of Freedom (MdoF). A 3D permeance network model is used to design the actuator and study its performance. The 3D-FEM is also used to investigate more accurately the prototype behavior. A prototype of the actuator has been built. Results, given by both models are shown and compared with those obtained experimentally.

L’objectif de ce papier concerne la problématique de dimensionnement de machines synchrones de faible puissance sous contraintes de diamètre extérieur, de couple et vitesse, de courant et de bruit émis. Une machine synchrone à aimants en surface avec un bobinage sur dents est comparée à deux machines synchro-réluctantes avec ou sans assistance d’aimants avec le même type de bobinage. L’objectif visé est de réduire le cout en essayant de conserver les mêmes performances sous contraintes. Des simulations éléments finis 3D permettent d’évaluer et de comparer les différentes structures proposées ainsi que des résultats expérimentaux. Mots-clefs : machine synchrone à aimants, machine synchro-réluctante, harmoniques de couple, harmoniques de forces radiales.

L’ajout d’aimants de compensation dans les espaces interpolaires de machines synchrones à pôles saillants permet d’atténuer les flux de fuites inducteur. Un prototype utilisant cette technique, dimensionné et construit, est étudié dans cette communication. L’effet de la compensation est d’abord illustré. Ensuite, le prototype est étudié en utilisant un modèle numérique. Différents points de fonctionnements sont simulés et les résultats sont comparés a des mesures expérimentales tant en grandeurs globales que locales.

Cet article brosse un panorama de la CAO en génie électrique. Une vision globale de la conception est d’abord introduite avant de présenter le processus itératif du prototypage virtuel avec quelques-unes des approches de modélisation classiquement utilisées pour évaluer les performances des convertisseurs électriques. L’accent est mis sur la nécessité de tenir compte de l’environnement d’utilisation du dispositif à concevoir et des différentes physiques mises en jeu ainsi que sur les stratégies d’optimisation types dans le processus de conception. Un éclairage est apporté sur les effets des procédés de fabrication, notamment pour distinguer le prototype virtuel du prototype réel. Enfin, la présentation de quelques axes de développements futurs dans le domaine de la CAO clôture l’article.