Zhigang Zhao

Analytical study and corresponding experiments for a new resonant magnetic charger with circular spiral coils

This study proposes a new resonant magnetic charger comprising circular spiral coils that operate with a strong coupling effect between the transmitter and the receiver. The two spiral coils are fitted with additional copper tapes to serve as resonant transmitter and receiver coils. The magnetic flux distributions are calculated using temporal coupled mode theory. Analysis results show that the proposed system can dramatically improve the efficiency and extend the power transfer distance. Experiments have been carried out in order to verify the performance of the system. In particular, the trends of output voltages when either the operating frequencies or the transfer distances are changing are reported. The system efficiency obtained experimentally is also given. Both calculated and measured results are in good agreement.

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

This paper presents a new dual-core closed-loop flux gate current sensor. The mathematical model was built, and the parameters that affect the characteristics of the flux gate current sensor were analyzed. The effects of the structural parameters on output characteristics of the sensor were simulated. Based on the simulation results, a prototype was designed, and the test results have a good agreement with the simulation results. The current sensor has the advantages of ultra low nonlinear error (u2009±u20093‰) and low offset error. The noise in the primary current is eliminated when measuring dc or ac signal. Especially, the designed dual-core closed-loop flux gate current sensor can measure current up to 20u2009kHz with the nominal primary current value ofu2009±u200930u2009A.

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

A novel 3-D magnetic properties tester for laminated silicon steel specimen has been designed and constructed. The magnetization structure is the critical part of the tester especially for the magnetic properties of the laminated silicon steel in perpendicular direction of grain oriented. To guarantee the experimental precision and accurately analyze the 3-D magnetic properties of the laminated silicon steel, a symmetrical 3-D magnetic flux path in the magnetization structure fit for given dimension of specimen has been calculated and modeled. Magnetic flux in each direction has been homogenized and concentrated on the top of the core poles through finite element analysis. Therefore, magnetic properties in each direction of the laminated specimen can be really concerned and analyzed in practical engineering.

The optimization of dual-core closed-loop fluxgate technology in precision current sensor

Right now, the diagnosis of coronary heart disease is mostly from experienced physicians judgment. How to use computer intelligent algorithms to aid in diagnosing of coronary heart disease has been a hot research of machine learning. This article will apply support vector machine (SVM) method which is based on the statistical learning theory to the diagnosis of coronary heart disease. On the basis of original data pre-processing and feature extraction, classifiers with different kernel are selected to classify the test data, followed by a comparison of classification results which show that the accuracy of classifiers with radial basis function is the highest. To select the best parameters of kernel function and penalty factor, Grid Search Method of optimizing parameters is used, which makes the classifier achieve the highest classification accuracy.

Design and Analysis of a Novel 3-D Magnetization Structure for Laminated Silicon Steel

The excitation conditions of electrical steel are generally sinusoidal but, with the advent power electronics in recent years, dc-biased excitation is sometimes experienced. In this paper, an efficient method for modeling the global magnetic properties of the silicon steel under dc-biased condition was proposed. The measurement was carried out based on a laminated core model of product level which was designed and made by the authors. However, the DC bias magnetic flux can not be measured directly in the experiment, and then a simulated method was presented to calculate the dc magnetic flux in the iron core. The calculation program was developed based on MATLAB, thus the hysteresis loops of the iron core under biasing magnetization were obtained. In addition, the experimental study on the iron loss of silicon steel was carried out. The different iron loss curves under various dc-biased magnetic field strength were determined. They are necessary for the analysis of dc bias magnetic field and electromagnetic design of products.

Studies on Application of Support Vector Machine in Diagnose of Coronary Heart Disease

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.

Magnetic Property Modelling of Laminated Silicon Steel Sheets under DC-Biasing Magnetization

When analyzing magnetic field distribution of the permanent magnets during the magnetizing process, it is important to couple the system equations of analysis method to the equation for the electric circuit. In this paper, the equations to calculate the residual flux distribution of permanent magnets using the T-Ω method taking into account the magnetizing process that uses the discharge current of a capacitor were developed. The effects of the eddy currents in the permanent magnet during the magnetizing process on residual flux distribution have been also analyzed. These calculated results are very useful for obtaining the optimum conditions for the magnetizing process. The effectiveness of the T-Ω method used in the magnetizing process of permanent magnets was certified by a comparison between the calculated average magnetization ratios and the measured ones.

Magnetic properties modeling of soft magnetic composite materials using two-dimensional vector hybrid hysteresis model

In order to evaluate the possible effects of electromagnetic irradiation of power lines on white mice, an electromagnetic environment was constructed in laboratory setting. Charge simulation method (CSM) and Biot-Savart law have respectively been adopted to compute the three-dimensional electric field and magnetic field of the environment. Both methods are programmed using the MATLAB software. Simulation and measurement indicate that the intensity of electric field can reach up to 10kil-volt per meter (kV/m) at ground level, and the magnetic flux density can reach as high as 100microtesla (μT). It is demonstrated that the electromagnetic environment can be utilized in studying white mice simultaneous exposure to extremely low frequency electric field and magnetic field emitted from power lines.