Fugui Liu

Improvement of the element-free Galerkin method for electromagnetic field calculation

The element-free Galerkin method (EFGM) is meshless method, it can solve some problems that the finite element method (FEM) can not solve effectively in electromagnetic field, such as thin plate problems, narrow gap problems, moving conductors, etc. In this paper, an improved formulation of the EFGM is proposed for electromagnetic field computations. Detailed research is conducted on some key problems, such as the selection of the weight function, the treatment of imposing boundary conditions and interface conditions. Finally, numerical examples are cited for demonstration.

Measurements and Calculation of Core-Based

An efficient method for modeling the global magnetic properties of the transformer under dc-biased condition based on a laminated core model of product level is proposed. The magnetic property data of the core under dc-biased condition are obtained, such as the Bm-Hb curve and hysteresis loops, which can be used in the analysis of dc-biased field and electromagnetic design of products. The exciting currents of dc-biased laminated core model are calculated and validated with the measured ones.

B-H

The excitation conditions of electrical steel are generally sinusoidal but, with the advent of power electronics in recent years, dc-biased excitation is sometimes experienced. The use of an iron core under dc-biased magnetization gives rise to asymmetrical hysteresis loops and the hysteresis loss in the iron core also increases with the value of dc excitation. For iron cores working with dc-biased excitation, accurate modeling of the nonlinear characteristics for the iron core that includes the dc-bias is very important for the computation of the exciting current and the iron loss. In this paper, an efficient approach for simulating the hysteresis loop of iron core under dc-biased excitation using neural-network theory is presented. The proposed method has the merits that a specific hysteresis loop can be identified conveniently and effectively to ensure that accurate electromagnetic-field analysis can be realized.

Curve and Magnetizing Current in DC-Biased Transformers

In this paper, the modeling of force sensors built with rare-earth iron giant magnetostrictive materials is studied. For such a purpose, a magneto-mechanical strongly coupled FE model is proposed. Using the proposed model, the input-output characteristic of a force sensor built with giant magnetostrictive material (Tb-Dy-Fe alloy) is calculated. The obtained results are compared with the measured ones to examine the validity of the proposed magneto-mechanical strongly coupled model and the FE implementation. Satisfactory agreements are achieved. This indicates that the proposed FE model can be used in the design and optimization of giant magnetostrictive force sensors

Modeling Magnetic Hysteresis Under DC-Biased Magnetization Using the Neural Network

A numerical model of displacement for a giant magnetostrictive actuator was founded. According to the model and the measured magnetic characteristic of giant magnetostrictive material, the relation between input current and output displacement for the actuator was calculated by means of the finite element method. A comparison between the calculating result and experimental one for the actuator was carried out and it was found that they were in agreement well. This demonstrates that the numerical model can be used for the design of giant magnetostrictive actuators.

A Magneto-Mechanical Strongly Coupled Model for Giant Magnetostrictive Force Sensor

A method is presented to optimize transverse flux induction heating (TFIH) inductor for a uniform temperature distribution. There were two neural networks used for eddy current and temperature field prediction respectively. The trained networks used for tested examples show a reasonable accuracy for the prediction, and then can be used for two purposes. One is to provide a good guessed value of the temperature dependent parameters for each finite element and an initial value for temperature field solution, which speeds up the iterative solution process for the nonlinear coupled electromagnetic thermal problems. The other is to be used in the optimization process.

A numerical model of displacement for giant magnetostrictive actuator

Soft magnetic composite (SMC) material produced by powder metallurgical techniques is assumed to be an isotropic material. It is applied in the core with special structure of rotating electrical machines, in which, the local magnetic flux density varies with time depend on both magnitude and orientation. Magnetic anisotropic feature may be shown in the material and influences the core operational performance. By using the designed 3-D magnetic properties tester, this paper presents the alternating and rotational magnetic properties of the SMC materials. Slightly anisotropic properties are found in hysteresis features and core loss distributions along different magnetization directions or planes. Experimental results show that some direction of the testing specimen seems harder to be magnetized than other directions. Milling and pressing process of the bulk specimen may cause changing of the grain size, micro-strain and pinning. These can influence the coercivity and remanence of the material and cause magnetic anisotropy, which may also be enhanced by increasing frequency and magnetization.

The use of neural networks combined with FEM to optimize the coil geometry and structure of transverse flux induction equipments

The geometry of real head has been modeled using MRI data set, and the electrical properties of head have been analyzed based on EIT using FEM method. The results show that surface potential distributions will vary with the change of conductivity inside head, and the variation will arrive at its maximum when the bone conductivity is changed. EIT system with 16 electrodes is able to reconstruct and display the approximation of the electrical conductivity of the head using the back-projection method by measuring the surface voltages of head. The data collection, processing and image reconstruction are performed using a computerized system. It is stable, convenient, in real time, and easy extendable.

Magnetic Anisotropic Properties Measurement and Analysis of the Soft Magnetic Composite Materials

A 2-D vector hybrid hysteresis model for a soft magnetic composite (SMC) material is established, which is combined with classical Preisach model and Stoner-Wohlfarth (S-W) model. The rotational magnetic properties of SMC materials were studied using the vector model, and the computed results were compared with the experimental measurement. It is shown that the vector hybrid model can effectively simulate the rotational magnetic properties under low magnetization fields.

Electrical characteristics of real head model based on electrical impedance tomography

In order to evaluate the effects of electromagnetic fields (EMF) of ultra high voltage (UHV) transmission lines exposure on important life organs and tissues of BALB/c mice, an exposed environment was constructed in laboratory. Fifty male adult BALB/c mice were divided into two groups. One group has been done by daily exposures of 24 hours, and the other sham-exposed group served as the control. After six weeks of exposure, all the mice were sacrificed. The important life organs of BALB/c mice in vivo were screened with serum biochemical assay, morphological observation at histological and ultrastructural levels as well as flow cytometric analysis (FCM). There were no significant differences in important organs and tissues except testis germ cells and bone marrow between exposed groups and control groups.