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Purpose This paper aims to propose a novel multiple transient modeling scheme for the 12-pulse phase-shifting reactor (PSR) rectifier to enhance the efficiency of full-cycle design evaluation. Design/methodology/approach The detailed time-domain method is adopted to model the rectifier at the behavioral layer. The diode bridges/transformer model at the architecture layer is established by using the switch function and Park transformation. The frequency domain model at the functional layer is derived with the time-varying Fourier decomposition and frequency-shifting. At the component layer, the magneto-thermal characteristics of the rectifier are analyzed with field-circuit and magnetic-thermal coupling methods. A computer-aided design program integrating multiple modeling is also developed for industrial product design. Findings The function layer modeling is preferred in the initial design stage, making up for the lack of modeling accuracy at the architectural layer and the lack of modeling rapidity at the behavioral layer. The component modeling is irreplaceable for the detailed evaluation in the latter design stage. The multiple modeling scheme based on the four-layer modeling helps the designers achieve high-quality products with a short development cycle. Originality/value The singular transient modeling cannot cover the needs of different stages in the full-cycle design evaluation. This paper fills this gap with a novel multiple modeling scheme. Meanwhile, the proposed multiple modeling scheme and developed computer-aided design program provide a great convenience for full cycle design evaluation of the 12-pulse PSR rectifier.

In this article, to accurately analyze the magnetic properties of high-temperature superconductor (HTS), a superconductor hysteresis model is proposed. Based on the physical mechanism, the hysteresis loop of HTS can be decomposed into an antimagnetic curve and a paramagnetic loop. The calculated and measured results of silver-sheathed Bi2223 superconducting tape samples under an external magnetic field are compared to show the effectiveness and accuracy of the presented method.

© 1965-2012 IEEE. This paper presents a quasi-3-D cylindrical coordinate high-Temperature superconducting (HTS) cable model based on the shell element theory. The quasi-3-D meshing elements are used instead of the traditional 3-D meshing elements to overcome the difficulties in meshing. The improved extended finite-element method (XFEM) is proposed to solve the field problem in close-jointed thin layers. The numerical simulation results are reported compared with the experimental test results for the case of an HTS cable with three layers.

In this paper, the extended finite element method (XFEM) is first applied to account for the weak discontinuity of the axisymmetric electrostatic field. Firstly, the interface between two materials in an element is described by the level set method. The enrichment function is used to modify the shape function of enrichment elements. Secondly, to illustrate the feature of the enrichment function, the distribution diagrams of enrichment functions in sub-elements are drawn. The 3D field can be simplified to an axisymmetric field, which can reduce the difficulty of calculation. Finally, models with bubbles in liquid nitrogen in the axisymmetric field are used to prove the reliability of XFEM. Compared with the conventional finite element method (CFEM), XFEM costs lower computing resources with almost the same computational accuracy.

In the actual operating circuit, the surface discharge of the insulator will be affected by air humidity. In order to study the influence of air humidity on the surface discharge characteristics of insulators, this paper firstly obtains the reduced electron mobility by assuming the electron energy distribution function (EEDF), and then builds a two-dimensional ceramic based on the fluid-chemical reaction insulator discharge mixed model which includes 41 kinds of reactions andl9 kinds of particles. According to the above model, the air composition is combined with the air humidity, and the distribution characteristics of the surface electron density, potential and ion density of the insulator under different air humidity are given. Finally, the discharge parameters of the insulators under different air humidity are analyzed and compared.

The finite element method has the characteristics of accurate calculation and convenient analysis of magnetic field and current distribution, so it has a good application prospect in the calculation of motor magnetic field distribution and loss. Taking a squirrel cage induction motor as an example, a two-dimensional finite element model considering skin effect, harmonic effect and saturation characteristics of the motor core is established. By using the finite element method, the transient magnetic field simulation of field-path coupling is carried out, and the copper loss of the motor is calculated. The classical Bertotti constant coefficient trinomial method was used to calculate the core loss. Considering the effect of rotating magnetic field and harmonic in the motor, the calculation method of core loss under the action of both is discussed. Finally, the total loss of the asynchronous traction motor is obtained and compared with the actual measurement results of the prototype. The error is small, which verifies the validity of the model.

Laminated busbar have the advantages of low impedance, good anti-interference, high reliability, space saving, easy installation, fast and so on. As a high-power modular connection component, it is widely used in wind power, photovoltaic, electric power and hybrid traction, power generation Systems, power switch systems, power conversion modules of electric equipment and other places. And it is indispensable part for the development of the power industry. Therefore, in the connection part of MMC sub-modules, laminated busbar are also used. This article first uses FEM Software to extract the stray inductance of the busbar of the module, highlighting the advantage of low stray inductance of the laminated busbar. Taking into account the DC short-circuit fault between the sub-modules, the temperature rise and deformation of the busbar caused by voltage changes are analyzed by using the electric field-heat transfer-structure three-field coupling method. And by changing the voltage level of the busbar and the operating time under a certain voltage level, the safe operating domain of the laminated busbar was judged, and the safe operating time and voltage were obtained.

The corona discharge of insulators has an important influence on the electromagnetic environment. In order to study the influence of different voltage polarities on the corona discharge characteristics of insulators, this paper is mainly based on the fluid-chemical reaction equation to establish a two-dimensional simulation model of insulators, which includes a variety of chemical reactions and substances. According to the above mentioned numerical analysis model, the electric field and the particle density of the insulators under different voltage polarities are given through the simulation calculation. Finally, the discharge parameters under different voltage polarities are compared, and the relationship between corona discharge parameters and voltage polarity is obtained.

The objective and constraint conditions for the optimal design of permanent magnet synchronous motors (PMSM) are generally non-linear numerical functions and multi-extreme functions of design variables. It is difficult to obtain optimal design parameters. This paper has completed the compilation of the electromagnetic calculation program for the motor, and introduced the genetic algorithm into the optimization design program, and we specifically use the genetic algorithm to optimize the magnetization length of the permanent magnet, the width of the permanent magnet, the air gap and the pole arc coefficient in the motor, and the goal was set to obtain the maximum efficiency. From the results, the optimization effect is significant, which fully demonstrates that the genetic algorithm can effectively improve the efficiency of the permanent magnet synchronous motor and shorten the design cycle.

It is very important to study the temperature rise of High Temperature Superconducting (HTS) transformer winding in short circuit. In this paper, the distribution of magnetic field and temperature field of MVA three-phase HTS transformer with high current carrying capacity is studied. Based on the finite element meth-od, the magnetic field distribution and AC loss of two-dimensional single-phase pan-cake winding model and cylinder winding model of HTS transformer are calculated respectively. Combined with the thermal parameters of liquid nitrogen and superconducting tape, the temperature field of two models is simulated and analyzed by finite element method. Based on the error analysis results caused by two-dimensional modeling, the electromagnetic field and temperature field distribution of high and low-voltage windings of HTS transformer under the condition of primary side short-circuit are calculated by using appropriate three-dimensional model of HTS transformer. The simulation results show that the heat dissipation performance of superconducting transformer is better than that of conventional transformer, which provides a theoretical basis for the design of HTS transformer.

This paper in magnetic troduces some research results about the magnetic characteristics on soft composite (SMC) material. Based on the mechanisms of magnetic material magnetization, a vectorial hysteresis model is proposed to simulate the hysteresis characteristics of SMC material. Meanwhile, by using the three dimensions magnetic properties test platform, the magnetic features of SMC material under different applied magnetic fields, such as alternating field and rotational field, have been measured. To verify this presented vectorial hysteresis model, a given SMC material is employed to be simulated and measured under rotating and alternating excitations, respectively. Compared with the two results, a good agreement can be obtained, which shows the validity and practicability of the proposed hysteresis model.

This paper introduces an elemental operator with biaxial anisotropy to simulate the scalar hysteresis phenomenon of the ferromagnetic materials. The equilibrium position of the magnetization for the elemental operator can be determined by energy minimization. To directly describe the magnetic properties of each operator, an improved analytical expression is deduced by the partial approximate substitutions. Moreover, this approach utilizes the concept of distribution function density in order to consider the interaction field and the coercive force of the elemental operators. To verify the presented model, the magnetic hysteresis of two different magnetic materials under alternating excitations is measured by the magnetic property measurement system and calculated by this elemental operator method, respectively. The comparisons suggest that this elemental operator is effective and can be a useful tool to simulate the scalar magnetic properties of ferromagnetic materials.

© 2017 IEEE. This paper presents a coupled field-circuit analysis method for the high-temperature superconducting (HTS) cable considering magnetic hysteresis by using the improved extended finite-element method (XFEM). The quasi-3-D cylindrical coordinate HTS cable model is first proposed based on the shell element theory. The quasi-3-D meshing elements are used instead of the traditional 3-D meshing elements to overcome the difficulties in meshing. A new Preisach type hysteresis model of HTS tapes is first combined with the improved XFEM to determine the magnetic hysteresis inductance. A magnetic field-circuit coupled program for current analysis of superconducting layers is coded. The numerical simulation results of this field-circuit coupled method are reported compared with the experimental test results for the case of an HTS cable with two layers.

© 1965-2012 IEEE. This paper introduces a temperature-dependent hysteresis model based on a vectorial elemental operator with temperature-sensitive spontaneous magnetization and biaxial anisotropy for the soft ferrites. Detailed analysis of the temperature-dependent magnetic properties of one elemental operator has been presented thereafter. With the help of the proposed vector elemental operator and the 2-D Gaussian distribution function, the temperature-dependent magnetic hysteresis of soft ferrites can be simulated. This model is validated by the substantial agreement between the simulated and measured major hysteresis loops of a soft ferrite sample Siemens 4C65 at different temperatures with slight acceptable error.

© 1982-2012 IEEE. The soft magnetic composite (SMC) materials and their application in electromagnetic devices have undergone significant development due to their unique advantages, such as low eddy-current loss, quasi-isotropy of mechanical and magnetic properties, low cost, and low material consumption during the production process. However, the magnetic properties of the SMC materials are very different from that of the laminated SiFe materials, which are particularly challenging for the design and application of electrical machines. This paper presents the modeling and measurement of magnetic properties of the SMC materials under both alternating and rotational magnetic excitations. Based on the underlying magnetization mechanisms, a vectorial elemental operator with biaxial anisotropy is introduced, and the concept of distribution function is utilized to describe the density of operators in the specimen. To verify this proposed model, the magnetic hysteresis of the SMC material is simulated and compared with the experimental results obtained by the three-dimensional magnetic property measurement system. The good agreement shows the validity and practicability of this vectorial elemental operator.

In the fabrication of soft magnetic composite materials, the iron powder particles are submitted to a high-pressure compaction process that should be considered in the modeling of magnetic hysteresis. This paper introduces a novel approach for modeling the stress-dependent magnetic hysteresis, based on the Stoner–Wohlfarth (S–W) model. Moreover, for determining the S–W particle equilibrium orientation directly, an extended S–W astroid method, which considering the stress effect, is presented. To verify this presented model, the magnetic hysteresis phenomenon of SOMALOY 500 are measured and simulated. The comparison between the two results shows that this model is feasible and effective, which can be applied to practical engineering.

In this paper, the extended finite-element method (XFEM) is used for modeling weak discontinuities in electric fields. For a weak discontinuous domain, the first-order derivative of the electric potential is discontinuous although the electric potential, degree of freedom, is continuous. In order to improve the approximation space of the conventional finite element method (CFEM), the enrichment function of the key of XFEM is used to model weak discontinuous solutions independent of the mesh. Interfaces among different materials can be described well by using the level set method. Numerical examples applied to the parallel plate electrodes in 1-D and the insulating oil with a bubble in 2-D static electric field involving error analysis, computational time, and electric field computations are provided to demonstrate the utility of XFEM in electric fields.

© 2018 KIEE EMECS (KIEE Electrical Machinery and Energy Conversion Systems). This paper introduces a vector hysteresis operator based on the physical mechanisms of the magnetic material. With the help of the schematic diagrams of energy barrier and the traditional wind-rose method, the magnetization orientation of each operator under different rotational magnetic field can be determined, as well as the rotation process of the corresponding magnetization. Meanwhile, a two-dimensional distribution function is utilized to describe the density of the interacting operators in the given specimen. To verify this rotational hysteresis model, the magnetic properties of soft magnetic composite SOMALOY™ 500 under different rotational excitations have been simulated and compared with the experimental results. Besides, the error analysis has been given to demonstrate the significance of parameters in the distribution function. The comparison shows the practicability of this vector operator and the wind-rose method.

The insufficient ability to withstand short circuit of power transformer seriously affects the safety of power system, so it is very necessary to calculate short circuit strength of windings accurately. Two-dimensional electromagnetic-structure coupling method is applied to calculate the mechanical properties of windings for a 110 kV power transformer and the stress and axial displacement of the transformer windings are analyzed and compared in short-circuit fault under the two kinds of commonly used preload loading modes, which are loading at one or both ends of the windings. The result reflects the stress and displacement distribution of the windings are different under the two kinds of preload loading modes. Considering the symmetry of the mechanical performance distribution of windings in practical engineering, the method of preload loading at both ends of the windings in numerical simulation of the mechanical performance of the windings is more accurate.

This paper presents a hysteresis model for the high-temperature superconductor using a simplified Preisach model, in which the Preisach distribution function is determined only based on the ${M}$ – ${H}$ limiting loop. The results of simulation and experiment of accuracy of the simplified Preisach model are reported for the case of silver-sheathed Bi2223 superconducting tape samples with an external magnetic field perpendicular to the tape surface.

In this paper, the extended finite-element method (XFEM) is employed to analyze electric field of insulating plate with crack. To begin with, both the approximation of XFEM and features of the enrichment functions for crack tip are presented. Then, XFEM is used to solve electric potential of an insulating plate with a middle crack, which proves the method can save computational time by comparison with classic finite-element method (CFEM) under the same computational accuracy. In addition, XFEM is also applied to calculate electrical field at crack tip of an insulating plate with an edge crack, which reveals that the relative error between XFEM and CFEM is small when the meshing size of CFEM around crack tip is smaller than that of XFEM. Therefore, electric field analysis of discontinuous and singular solutions can demonstrate the superior performance of XFEM.

This paper proposes an improved extended finite element method for modeling electromagnetic devices with multiple nearby geometrical interfaces. In regions near these interfaces, the magnetic vector potential approximation is enriched by incorporating multiple derivative discontinuous fields based on the partition of unity method such that the interfaces can be represented independent of the mesh. The support of a node or an element can be cut by several interfaces. This method results in the high accuracy in the approximation field and derivative field. Numerical examples applied to the iron core in 1-D eddy current field involving level set-based parts, error analysis, and electromagnetic field computations are provided to demonstrate the utility of the proposed approach.

Background The clinical efficacy of furosemide administration in preventing contrast-induced nephropathy (CIN) remains uncertain. This meta-analysis was designed to update data on the incidence of CIN with additional furosemide treatment beyond saline hydration in comparison with hydration alone in patients undergoing percutaneous coronary intervention (PCI). Material/methods A computerized literature search of MEDLINE, EMBASE, and Cochrane databases was performed. Trials were eligible if they enrolled patients undergoing coronary angiography and randomly allocated participants to receive furosemide administration in addition to saline hydration or saline hydration alone. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) for combinations of studies. Results Five trials involving 1294 patients (640 for additional furosemide treatment and 654 for hydration alone) were included in the meta-analysis. In the synthesis of data, additional furosemide administration had little impact on the incidence of CIN post-PCI compared with peri-procedural saline hydration alone (OR=0.96; 95% CI 0.33-2.84, p=0.95). Moreover, as for the subsequent need for dialysis, there was no statistical significant difference between the 2 groups (OR=1.01; 95% CI 0.38-2.67, p=0.99). Sensitivity analyses did not show any relevant influence on the overall results. There was no publication bias in the meta-analysis. Conclusions Furosemide administration did not achieve additional benefit beyond saline hydration in reducing the incidence of CIN in patients undergoing PCI.

© 2017 IEEE. This paper introduces a comparative study of two different hysteresis models, limiting loop model and elemental operator model. The former is regarded as a mathematical approach based on the traditional Preisach model. To circumvent the difficulty of determining the distribution function in the Preisach model, the data of the limiting hysteresis loop and a function transform on the Preisach diagram are employed. The latter is a physical method which adopts a vectorial elemental operator with biaxial anisotropy based on the magnetization mechanisms of the ferromagnetic material. These two models are analyzed and compared in terms of the underlying principle, numerical implementation, and calculation accuracy in this paper. To verify the introduced models, the magnetic properties of non-oriented silicon steel Lycore-140 and soft magnetic composite material Somaloy 500 under alternating excitations are measured and compared with simulated results, which show the validity and practicability of the models but with different calculation accuracy and speed.

Background: Long-term outcomes of drug-eluting stents (DES) versus bare-metal stents (BMS) in patients with ST-segment elevation myocardial infarction (STEMI) remain uncertain. Objective: To investigate long-term outcomes of drug-eluting stents (DES) versus bare-metal stents (BMS) in patients with ST-segment elevation myocardial infarction (STEMI). Methods: We performed search of MEDLINE, EMBASE, the Cochrane library, and ISI Web of Science (until February 2013) for randomized trials comparing more than 12-month efficacy or safety of DES with BMS in patients with STEMI. Pooled estimate was presented with risk ratio (RR) and its 95% confidence interval (CI) using random-effects model. Results: Ten trials with 7,592 participants with STEMI were included. The overall results showed that there was no significant difference in the incidence of all-cause death and definite/probable stent thrombosis between DES and BMS at long-term follow-up. Patients receiving DES implantation appeared to have a lower 1-year incidence of recurrent myocardial infarction than those receiving BMS (RR = 0.75, 95% CI 0.56 to 1.00, p= 0.05). Moreover, the risk of target vessel revascularization (TVR) after receiving DES was consistently lowered during long-term observation (all p< 0.01). In subgroup analysis, the use of everolimus-eluting stents (EES) was associated with reduced risk of stent thrombosis in STEMI patients (RR = 0.37, p=0.02). Conclusions: DES did not increase the risk of stent thrombosis in patients with STEMI compared with BMS. Moreover, the use of DES did lower long-term risk of repeat revascularization and might decrease the occurrence of reinfarction. Fundamento: Os resultados a longo prazo dos stents farmacológicos (SF) contra stents convencionais (SC) em pacientes com infarto do miocárdio com elevação do segmento ST (IMEST) permanecem incertos. Objetivo: Investigar os resultados a longo prazo dos stents farmacológicos (SF) contra stents convencionais (SC) em pacientes com infarto do miocárdio com elevação do segmento ST (IMEST) . Métodos: Foi realizada pesquisa de dados nas bases de dados MEDLINE, EMBASE, na Cochrane Library, e na ISI Web of Science (até fevereiro de 2013) para estudos clínicos aleatórios que comparam a eficácia durante mais de 12 meses ou a segurança do SF com SC em pacientes com IMEST. Foi apresentada uma estimativa agrupada com risco relativo (RR) e seu intervalo de confiança de 95 % (IC), utilizando modelo de efeitos aleatórios. Resultados: Dez estudos com 7.592 participantes com IMEST foram incluídos. Os resultados gerais mostraram que não houve diferença significativa na incidência de morte por todas as causas e trombose de stent definida/provável entre SF e SC em seguimento de longo prazo. Os pacientes que receberam implante de SF pareciam ter uma incidência de infarto do miocárdio recorrente inferior a1 ano que aqueles que receberam SC (RR = 0,75, 95% CI 0,56-1,00, p = 0,05). Além disso, o risco de revascularização do vaso alvo (RVA) depois de receber o SF diminui consistentemente durante a observação a longo prazo (todos p

© 2016 IEEE. This paper proposes a vectorial magnetic hysteresis model based on a vectorial elemental operator and its distribution function to represent the magnetization mechanisms of soft magnetic materials. The magnetic hysteresis of a soft magnetic composite material under rotational magnetization is simulated and compared with the experimental results.

This paper simulates the melting process and liquid titanium droplet formation in electromagnetic levitation melting (EML) process by using the finite element method. The modelling of the physical EML process involves the coupling of electromagnetic, thermal, and fluid flow fields. The bidirectional interactions of different fields are also consided. The electrical parameters, such as frequency, current, and number of turns of the excitation coils, which might affect the size of droplet, are studied. The arbitrary Lagrangian-Eulerian formulation is employed to model the deformation of metal sample during the melting process. The results show that the method adopted in this paper could dynamically predict the melting process, and size of the droplet could be controlled by modifying the electrical parameters.

© 2016 IEEE. This paper introduces a temperature dependent hysteresis model based on a vectorial elemental operator with temperature-sensitive spontaneous magnetization and biaxial anisotropy for the soft ferrites. This model is validated by the substantial agreement between the simulated and measured major hysteresis loops of a soft ferrite sample at different temperatures.

In this paper, a DC voltage pulse injection based method is proposed to detect the initial position and rotor polarity of permanent magnet synchronous motor (PMSM). The rotor angle vibration is expressed analytically as a function of the injected pulse. The nonlinear numerical simulation model of PMSM is employed, in which the saturation saliency is incorporated as well as the structural saliency. The proposed scheme is simulated and verified by using the nonlinear model and a 2-D finite element method (FEM) algorithm, respectively. The initial position detection is tested at different starting positions and the results show that the proposed scheme can be used to identify the PMSM initial rotor position. © 2006 IEEE.