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This paper addresses the influence of the primary and secondary resistances on the behavior of minor hysteresis loops when the electromagnetic device is fed by three-level PWM (pulse width modulation) voltage. To study the device transferring energy to a load, the experimental approaches are different of traditional procedures to material characterization, where problems inherent to the process are added. Analytical, FEM and experimental analysis are performed on a toroidal transformer equipped with a flux sensing coil. The leakage fluxes related to the primary and secondary currents are shown to cause errors in the measurement of the core magnetization current. A solution to mitigate this problem is employed, consisting in twisting and winding together primary and secondary conductors. Experimental methodologies for obtaining the value of the iron losses when the device is transferring energy to a load are also performed. The study shown showed that supply voltage with three-level PWM waveform causes minor hysteresis loops and the greater the resistance value of the excitation winding, the larger the areas of the minor hysteresis loops. On the other hand, by increasing the energy transferring to a load the minor loops areas tend to decrease.

Compressors operating in refrigeration systems, typically with built-in induction motors, represent an important energy demand. The applicability of standard methods for efficiency determination of induction motors is limited in this context by the constructive characteristics of these motors, such as the shared compressor frame and the inaccessibility of the shaft. The main contributions of this paper are to provide an overview of standard and alternative methods for efficiency testing of single and polyphase motors, according to technical standards and to the state of the art, and to offer guidelines for the method selection. The options cover dynamometer tests, loss segregation and equivalent circuit methods, some even applicable without direct access to the motor. Experimental application examples in single and three- phase motors are presented. Beyond the context of compressors, the discussion is relevant for inaccessible motors in general.

The purpose of this paper is to describe the methodology adopted to design an electric motor applied to the traction of a single-seat high-performance electric vehicle. A comparative selection of topologies of electrical machines is made and then, an analytical model of the chosen layout is described. An evolutionary algorithm is used in order to find an optimized solution according to some selected performance criteria. Afterwards, the analysis of the selected design is made in a finite element simulation software. Finally, a comparison between the analytical and the finite element models results is performed.

In a previous article, the ferromagnetic hysteresis G model was proposed. One of the relevant advantages of the G model is its simplicity compared with classical methods. Here, we present the first steps to insert the model in a 3-D finite-element code. This model uses analytical curves to describe the hysteresis loop. Also, as a contribution, the Elliot transfer function is modified on the way it matches the experimental B(H) curves with good accuracy. Therefore, the main goal here is to investigate its robustness and accuracy when treating the benchmark case Testing Electromagnetic Analysis Methods (TEAM) Problem Number 32. Initially, the G model is presented in a succinct way. Then, the parameter characterization of the modified Elliot transfer function is explained and discussed. This modified Elliot function, coupled with a 3-D FE code, is compared with a similar implementation using the Jiles-Atherton method and experimental data.

In a previous work, a hysteresis modeling, called G model, was proposed with the goal of describing this phenomenon by simple equations. In that work, we developed the direct model which uses the magnetic field as the independent variable. However, with the magnetic vector potential 2-D classical formulation, the magnetic induction is the independent quantity. The main contribution of this work is to present the inverse version of the G model adapted to vector potential formulation. In addition, a Mayergoyz vector hysteresis generalization is applied in order to consider rotational fields and couple the model with a 2-D vector potential finite-element method (FEM) formulation. In this approach, the anisotropy is inserted with the orientation distribution function (ODF).

Based on multiscale modeling of the anhysteretic magnetization considering mechanical stress and crystallographic texture effects, an extension of the Jiles-Atherton (J-A) hysteresis model is proposed. The magnetization and the volume fractions given by the multiscale approach are advantageously used in the J-A model to modify the anhysteretic magnetization and the pinning parameter. The parameters of the proposed model are identified in order to fit with the characterization results under compressive stress using two sets of experimental data. Using the same optimized parameters, the model is tested for the representation of loops under other stress conditions to evaluate its prediction capabilities.

In this paper, we propose the G model, a new approach for modeling hysteresis based on simple equations and having its treatment more direct than, for instance, the well-known Preisach and Jiles–Atherton models. As main basis, the shape of the external hysteresis curves is strongly considered, allowing a correct behavior of magnetic induction evolution inside the hysteresis cycle. Minor loops can also be represented with good accuracy. Comparisons with the Jiles–Atherton model and experimental data are shown in order to validate the proposed methodology.

This work points out the origin of the convergence problem when the Jiles-Atherton hysteresis model is associated with the finite elements method (FEM) to analyze electromagnetic devices. To overcome this problem, a restriction is proposed and applied in the classical approach for the determination of the Jiles-Atherton hysteresis model parameters process. The presented methodology considers the inverse model, where the magnetic induction is the input variable and the magnetic field is the output variable.

This paper presents numerical procedures for the treatment of tensors related to the vector Jiles-Atherton (JA) model applied to the finite element method (FEM). The method is based on the 3-D differential permeability formulation. A more precise calculation implies the determination of the off-diagonal terms of tensor parameters. The main goal is to verify if such a change improves the convergence stability of the model coupled with FEM and if the use of the JA off-diagonal terms yields a more accurate hysteresis representation. We present results comparing experimental data of the Testing Electromagnetic Analysis Methods problem 32 with the proposed method.

Due to differences in the manufacturing process, centrifuged rotors have higher efficiency and interbar resistance than those produced by the high-pressure die-casting process. Therefore, the annealing applied to high-pressure die casted rotors to improve the insulation of the cage is not traditionally applied by manufacturers to centrifuged rotors. This study evaluates the effect of the traditional 450 °C heat treatment on centrifuged rotors, as well as the feasibility and effects of 520 oC rotor annealing, temperature not recommended for high-pressure die-casted rotors. The efficiency measurements were performed with a dynamometer, using small single-phase motors, usually applied in domestic refrigeration compressors, with a standard stator kept under controlled conditions. A structured test was performed to assess the effects in a mass production scenario, aiming to reflect the variation of the production parameters within the manufacturer specifications.

Magnetoelastic couplings in ferromagnetic materials can be modelled using multiscale approaches. Various degrees of sophistication are accessible depending on the foreseen material and application. Here, we present a set of models, built on this approach, which can be used for devices magnetic field analysis. The representation of combined crystal anisotropy and texture effects is analysed through the introduction of a simplified fiber texture. A method is also proposed for the computation of magnetostriction hysteresis together with magnetization by association with a Jiles-Atherton model. All the models are detailed with their main physical and numerical characteristics, and the whole set of features that are needed for their use in device simulation tools. A test structure is finally simulated using the finite element method in order to illustrate the possibilities offered by these multiscale approaches.

The Jiles-Atherton scalar hysteresis model presents five parameters used to represent the material tested and used to calculate the magnetic losses. This article presents a comparative analysis of the performance of two methods of identifying these parameters. In the first method, the equations of Jiles-Atherton were assembled into a single non-linear ordinary differential equation as a function of the variables of interest. An algebraic system of five equations with five unknowns is obtained by evaluating the non-linear ordinary differential equation in five points belonging to the branch of the experimental hysteresis loop. The parameters are obtained by solving this system of equations using the method of Non-Linear Least Squares (NLLS). In the second method, the inverse model of Jiles-Atherton is used to calculate the magnetic field H from the experimental values of magnetic induction B. Using the method of genetic algorithms (MGA), the objective function given by the sum of the relative error of calculated magnetic field and experimental magnetic field along the hysteresis loop is minimized. To validate methods the experimental curves were compared with calculated ones. When applying the methods, it was verified that NLLS besides providing more accurate results, it is faster when compared to MGA. In the MGA the convergence of the calculated magnitudes to the experimental magnitudes improves when one of the chromosomes of the initial population is the solution obtained applying NLLS.

International audience; A simulation model of an ironless Axial-Flux Permanent-Magnet (AFPM) machines is presented. Indeed as accurate analytical methods do not yet exist for ironless AFPM, 3D Finite Element Analysis (FEA) is required at each time of an operating point. The purpose of this article is to show that for any operating point of the motor, the torque can be calculated from the distribution of the axial magnetic flux density obtained from only one 3D FEA. The proposed simulation model is validated by using a prototype of an AFPM ironless whose non-active parts are additively manufactured. This first step through the 3D printing technology is simplified by the use of cylindrical magnets and plastic mechanical supports.

The magnetic losses behavior on electrical steels related to the magnetic aging is analyzed in this paper. Experimental procedures involving thermal, metallurgical, and electromagnetic measurements were performed. The evolution of the losses is modeled using a scalar hysteresis model, and the aging prediction on electrical motor steels is proposed using the Arrhenius formula. The proposed study brings relevant information to be considered on designing electrical motors.

This paper discusses the implementation of the inverse Jiles–Atherton vector hysteresis model with the 2-D Finite Element Method (FEM) for the analysis of an induction machine operating as self-excited generator. A differential reluctivity tensor couples the hysteresis model with the magnetic vector potential-based finite-element model. Experimental and simulated results (transient and steady state) are presented.

The finite-element calculations and experimental measurements are employed in this paper to detect faults in a two-pole synchronous generator. A special benchmark constructed for this study allows imposing short circuits in the rotor winding, and it is used to verify the numerical results. The air-gap magnetic field can be detected by means of sensors placed inside the machine, and it can be calculated by the finite-element method (FEM) as well.

This paper describes a new test device that allows a better evaluation of the magnetic losses generated in the ferromagnetic core of the stator of three-phase rotating electrical machines. One of the main advantages of this electromagnetic testing device—from here called “Tester”—is its ability to measure the magnetic losses in all parts of the sample (teeth and yoke), which is an advantage comparing with the Core Test. The magnetic flux generated by the proposed Tester has the same characteristics of the flux generated in induction motors, allowing a better assessment of magnetic losses in electrical steel sheets. Three different suppliers of the same electrical steel were evaluated with the aim to compare the results of three experimental methods: 1) Epstein frame; 2) electric motors tests (no-load tests); and 3) the tester here presented.

This paper presents a methodology based on genetic algorithms and heuristic relationships for the determination of all parameters of the equivalent circuit of induction motors from manufacturer catalog data. The approach employs the complete steady state model of the motor and aims at the calculation of efficiency, power factor, current, torque and other quantities at any load. The methodology consists of a first stage, in which a search space for the genetic algorithm is determined, and a second stage in which the circuit parameters and auxiliary slip values are determined. Three different types of motors were investigated, with pole number and power varying from 2 to 6 and from 10 hp to 100 hp, respectively. The accuracy is verified based on deviation from catalog data, reference parameter values obtained experimentally and experimental data. Results indicate that the proposed methodology is capable of finding parameter values which fit the catalog data, although the inaccuracy of these data causes deviation from reference parameter values. The used heuristics is shown to reduce the deviation of less sensitive parameters.

Statics and Quasi-Statics Electromagnetics - Brief Presentation Introduction The Maxwell Equations The Maxwell Equations: Local Form The Maxwell Equations: Integral Form The Maxwell Equations in Low Frequency The Electrostatics Magnetostatic Fields Magnetic Materials Inductance and Mutual Inductance Magnetodynamic Fields Fields Defined by Potentials Final Considerations References Ferromagnetic Materials and Iron Losses Introduction Basic Concepts Losses Components Iron Losses under Alternating, Rotating and DC Biased Inductions Final Considerations References Scalar Hysteresis Modeling Introduction The Preisach's Scalar Model The Jiles-Atherton Scalar Model Final Considerations References Vector Hysteresis Modeling Introduction Vector Model Obtained with the Superposition of Scalar Models Vector Generalizations of the Jiles-Atherton Scalar Models Some Remarks Concerning the Vector Behavior of Hysteresis Final Considerations References Brief Presentation of the Finite Element Method Introduction The Galerkin Method: Basic Concepts using Real Coordinates Generalization of the FEM: Using Reference Coordinates Numerical Integration Some Finite Elements Using Edge Elements References Using Nodal Elements with Magnetic Vector Potential Introduction Main Equations Applying Galerkin Method Uniqueness of the Solution the Coulomb's Gauge Implementation Example and Comparisons Final Considerations References The Source-Field Method for 3D Magnetostatic Fields Introduction The Magnetostatic Case - Scalar Potential The Magnetostatic Case - Vector Potential Implementation Aspects and Conventions Computational Implementation Example and Results References The Source-Field Method for 3D Magnetodynamic Fields Introduction Formulation Considering Eddy Currents - Time Stepping Formulation Considering Eddy Currents - Complex Formulation Field-Circuit Coupling Computational Implementation The Differential Permeability Method Example and Results References A Matrix-Free Iterative Solution Procedure for Finite Element Problems Introduction The Classical FEM: T-Scheme The Proposed Technique: N-Scheme Implementation Convergence Implementation of N-Scheme with SOR Applying Non-Stationary Iterative Solver to the N-Scheme CG Algorithm Implementation Examples and Results Results and Discussion References

An accurate modeling of materials is essential to obtain reliable results in fields calculation. The Jiles-Atherton approach is widely used for modeling the magnetic hysteresis and depends on its set of five parameters to properly represent material. In this article is proposed an original methodology for obtaining this set of parameters avoiding the derivatives rough calculation and using the calculation of integrals. From the model equations, a new methodology with two nonlinear algebraic systems of five equations in five unknowns is obtained. The initial magnetization curve, the anhysteretic curve and filtering data are not necessary. The proposed methodology also does not restrict the search space of parameters. The parameters assume values in the interval (0,∞). Calculated data were compared with experimental data to validate the methodology. The simulations showed that the proposed method can obtain an accurate set of parameters from a single experimental hysteresis loop and with low computational effort.

This paper presents an equipment dedicated to the monitoring of synchronous generator through the measurements of the external magnetic field time derivative. The equipment uses a methodology which can be an additional technique to those applied currently on the faults detection, mainly when monitoring the incipient faults type. Based on frequency spectra (magnetic signatures), the faults detection is performed by the analysis of the components evolution. As it is not possible to test the ability of the equipment in detecting several types of faults of generators faults in a power plant, a testbench was constructed for this purpose. Faults inserted deliberately in the generators of the testbench are detected by the equipment, showing its capacity. This equipment has been also installed in power plants.

International audience; In the previous work, we introduced a formulation joining two concepts: 1) the source-field technique and 2) the differential permeability method. It was shown that the resulting procedure produces accurate results for non-linear cases and it was favorably compared with the more classical approach considering the actual permeability. Here, we extend this formulation for vector hysteresis cases that are modeled by the Jiles-Atherton approach. It considers the magnetic anisotropy of the ferromagnetic sheets.

This original proposed method is based on rewiriting the equations of the inverse model and the equations of Jiles-Atherton hysteresis model in order to include the total derivatives of quantities concerned. A sixth parameter represents these insertions. Compared to other already proposed methods, this approach does not limit the values assumed by the parameters, here it can take positive real values, the initial and anhysteretic magnetization curves and filters are not used. The sixth-parameter is added to improve the model adaptability to the experimental behavior when a non smooth and noisy loop is considered.

In this work two vector hysteresis models are incorporated on field calculations. Performance comparison of the two methodologies is presented. The Jiles-Atherton vector model and the Vector Play Model are coupled with FEM. Special attention is paid to convergence issues.

This paper discusses the implementation of the inverse Jiles-Atherton vector hysteresis model with 2-D finite element (FE) method for the analysis of a hysteresis motor electromechanical behavior. A differential reluctivity tensor couples the hysteresis model with the magnetic vector potential-based FE model. Simulation results are validated by experimental data obtained from a specially designed machine.

Several methods have recently been proposed to identify the parameters of Jiles-Atherton model, e.g. differential evolution method, particle swarm optimization, and optimization branch and bound. In this work, it is presented a simplified method that avoids the rough calculation of derivatives, the rough calculation of integrals and avoids filtering data during the processing of the material characterization. Other advantages of proposed method are speed in the parameter calculation, the initial and anhysteretic magnetization curves and restrictions on the search space of parameters are not used, the search space of parameters is wide ranging from zero to infinity, it uses a trust region strategy to improve the robustness when the initial set of parameters is far from solution. In order to validate the method, simulated loops are compared with experimental ones.

The here proposed method is based on rewriting the equations of Jiles-Atherton model to obtain a single non-linear ordinary differential equation used to identify the parameters. This equation involves only the interest variables: H, B with known values, and the model parameters with unknown values. The initial and anhysteretic magnetization curves, and filtering data are not used. The search space of the parameters is not restricted. The model parameters are readily obtainable. To validate the method, experimental data are compared with calculated data.

Finite Element Methods (FEM) and Particle Swarm Optimization (PSO) have been used as solution for many electromagnetic problems and modeling. This paper presents a computational system combining a validated FEM solver and PSO techniques for electromagnetic optimization problems. The case considered here is an ideal cylindrical Halbach Array of permanent magnets, whose results are compared to ideal models in order to validate the optimization procedure.

A new designed core tester and its feeding and control devices are presented in this paper. With this workbench, mounted single phase induction motor stators can be magnetically fed with controlled induction waveforms in order to evaluate their quality in the industrial environment. As the measured data involves the machine stator as well as the core of the testing apparatus, Finite Element and iron losses modeling are employed in this paper in order to distinguish the losses of the stator under test and the losses of measurement device itself. Therefore, the main goals of this paper are to propose a new tester design as well as a numerical way allowing the separation of the losses in the stator under test and the losses inherent to the tester itself.

The flux density waveform in the stator of a rotational electrical machine or three-phase transformer is typically bidirectional in many regions of the core. However, rotational magnetic flux can be observed in some parts of their magnetic circuits. The iron core under rotational flux presents magnetic losses, usually, greater than the alternating ones, for a same flux magnitude. The magnetic behavior of materials under rotating flux is extremely complex and can not be represented with hysteresis or conventional magnetic losses models. The vector hysteresis model of Jiles-Atherton has been shown effective in modeling rotating flux for isotropic and anisotropic materials. It is observed that the rotational losses increase with the increase of excitation frequencies. In this work, the iron losses behavior is investigated under rotational flux by combining the Jiles-Atherton vector hysteresis, eddy currents and excess losses models. Experimental curves are obtained from a rotational single sheet tester and the losses components are analyzed.

In this paper, the authors deal with the finite-element (FE) modeling of eddy-current effects in form-wound windings of electrical machines using a previously proposed general frequency- and time-domain homogenization method. By way of demonstration and val- idation, a real-life 1250-kW induction machine with double-layer stator winding is considered. The skin and proximity effects in one stator conductor (copper bar) are first quantified by means of a simple low-cost FE model, leading to complex and frequency-dependent coefficients for the homogenized winding (reluctivity for proximity effect and conductivity or resistance for skin effect). These com- plex coefficients are subsequently translated into real-valued and constant coefficients that allow for time-domain homogenization when introducing a limited number of additional degrees of freedom in the FE model. All results obtained with the homogenized model (con- sidering one conductor or a complete slot) agree well with those produced by a brute-force approach (modeling and finely discretizing each conductor). ispartof: IEEE Transactions on Magnetics vol:46 issue:8 pages:2852-2855 ispartof: location:BRAZIL, Santa Catarina status: published

The source-field method is a very effective way to treat 3-D magnetostatic and magnetodynamic cases for linear and nonlinear studies. In this paper, we propose a variation of this method based on the concept of differential permeability. With this new approach, it is possible to handle nonlinear cases and also more complex hysteretic materials. In this work, we will present the method and consider the first case. The electric circuit is coupled with the magnetic structure and a time stepping technique is used.