The H-matrix-based preconditioning has been improved, and the performance of the ICCGH incorpo- rated with the proposed preconditioning has been investigated numerically. The result of computations shows that the modified ICCGH is faster than the conventional one.

In inductors driven by the inverter using GaN devices, the ringing phenomenon, which occurs due to the multi-resonances during the short rising and falling time, increases noise and loss. To clarify the mechanism of the multi-resonances, the high frequency behaviors of a ring core inductor in frequency domain are simulated by using the 2D electromagnetic field finite element analysis taking account of the stray capacitance. Moreover, to explain this phenomenon, a distributed-element circuit model including the stray capacitance is proposed based on the simulated results. It is shown that the proposed finite element and circuit models can represent the measured HF behaviors of the ring core inductor.

This paper presents mechanism and calculation of multipoint grounding current of converter transformer core. Firstly, the core multipoint grounding equivalent circuit and the circuit impedance calculation method are given and the analytical calculation under harmonic and DC bias is carried out. Secondly, the anisotropic resistivity matrix based on the homogenization modeling theory is given and the FEM calculation under harmonic and DC bias is carried out. Then, the core multi-point grounding test based on the converter transformer model was carried out under harmonic and DC bias is carried out. Finally, the mechanism of multipoint grounding current of core is given, and correctness of the calculation method is verified.

To clarify the mechanism of the excess loss in a Non-Oriented (NO) electrical steel sheet, a modeling of excess loss taking account of the variation of grain orientation is proposed in this paper. In the proposed method, the NO steel sheet is modeled by grains with random orientations, then an uniaxial anisotropic magnetic characteristic is considered in each grain. The nonlinear eddy current analysis of a simple model composed of cubic grains with different easy axes is carried out by using the initial anisotropic BH curves of a Grain-Oriented steel sheet. Then, the calculated eddy current loss is compared with the measured values of an actual NO steel sheet. It is shown that the proposed model can represent the excess loss in low flux density region, but not in high flux density region.

Transformer bushing is an important part of transmission engineering, its structure safety is very important. In this paper, the failure of the conductor rod of the high voltage bushing of a 750kV transformer is analyzed. The high voltage bushing of this transformer is made of oil paper capacitive structure. The conductor rod used to transport the current inside the high voltage bushing bears the current and the tension from the pressing spring. Based on the finite element simulation and experimental research, this paper analyzes the fault cause is the insufficient strength of the conductive rod connector, and gives the operation and maintenance suggestions.

In recent years, wearable devices have become increasingly important in improving quality of life. Wireless power delivery to such devices is a promising technology for the miniaturization. Magnetic resonant wireless power transmission is a suitable method for such applications. The operating frequency should be varied corresponding to change the coupling coefficient. Recently, use of power oscillators in the transmission circuit is investigated for such cases. An LC power oscillator is one of the candidates for such applications because of the high efficiency and the simple circuit configuration. In this paper, an improved LC power oscillator suitable to wireless power transmission was proposed and the power efficiencies between the parallel and series configuration for the receiver circuit were compared.

The novel preprocessing method to improve the prediction accuracy of deep learning (DL) has been proposed. In the proposed method, the Empirical Mode Decomposition (EMD), one of the frequency decomposition methods, is applied to the gap magnetic flux density distribution, the input data of DL. The method is applied to DL to predict motor characteristics.

In semiconductor manufacturing, the process of manufacturing various components and wiring on silicon wafers requires high cleanliness. Although traditional magnetic levitation slider devices can eliminate mechanical contact and suppress dust, suspension devices, and propulsion devices are usually used separately. The actuator using a linear motor generates about 10 times the suction force in the upward direction compared to the driving force. Applying it to upward buoyancy can improve energy utilization and simplify the structure [1]. This study used four sets of E-type electromagnets to design a linear slider that can simultaneously utilize buoyancy and propulsion forces. By using an E-type iron core, the electromagnet can be miniaturized. Replace the torque in the rotating electric motor with propulsion force, and replace the bearing support force with buoyancy force. Through suspension and disturbance experiments, the device was subjected to a 1N impact and returned to stability after 3 seconds. The experimental results proved that the device has good response characteristics.

this paper investigates the dynamic modeling and optimization of a V-type energy harvester. The research of energy harvester pays more and more attention to practicality. Therefore, an new energy harvester is designed, which can be placed under the soles of people’s shoes. Firstly, the model of V-type energy harvester is designed, and the mechanical model is established to analysis the natural frequency. Two V-type energy harvesters are combined into one Z-type energy harvester. Secondly, the finite element analysis of V-type and Z-type energy harvesters are carried out, and the displacement, stress, strain are pointed out. Furthermore, the natural frequency is compared with the theoretical value, and the maximum strain position is pointed out. The results show that the modeling method and analysis results are correct.

A magnetic-geared motor (MGM) with permanent magnets only in its stator is proposed. The MGM can control the maximum transmission torque utilizing DC currents. In addition, low-speed rotor torque due to coil currents is larger compared with conventional MGMs. Therefore, the dynamic characteristics of the proposed MGM are different from that of conventional MGMs. In this paper, firstly, a mathematical model of the proposed MGM is created. Secondary, the electric circuit equation of the proposed MGM is described, and physical quantity maps are introduced. Finally, the simulated relationship between the phase angle difference of the rotors and load is compared with finite element analysis under vector control.

An investigation into the impact of atmospheric fine particles on the ionic mobility is presented. A measurement apparatus was designed using direct current corona discharge at room temperature. Positive and negative ionic mobilities were extracted from the electric field and ion current density measured in the apparatus. With the presence of fine particles, equivalent ionic mobility was found to decrease exponentially with the mass concentration of the fine particles. Distributions of the electric field and space charge density, and the contributions to the charge density from small ions and charged fine particles were also calculated.

This paper presents a new optimal design method for a PM motor based on loading separation. Using the relationship between the loadings of the power equation and the motor’s geometries, it is revealed that the arbitrary selection of four variables p, Dg, Lstk and gm provides a unique motor with the required output power. Consequently, the optimal design is determined through characteristic evaluation and comparison of the motors designed with a myriad combination of four independent variables. To verify the validity of the proposed method, an optimal design is performed for a 5 kW SPMSM and the performances are analyzed.

This paper investigates one of the key equipment in UHVDC transmission, which is the converter transformer. The harmonic current generated by the converter can cause localized overheating in the transformer windings. Finite element models of the magnetic field and thermal field of the core winding are established based on experimental data. Finite element simulation results are provided for sine excitation, rated excitation, and variations in winding conductivity with temperature. Finally, the hot spot temperature of the winding is verified using analytical and the experimental scaling model, confirming the necessity of considering harmonic current and variations in winding conductivity with temperature.

To aim to achieve portable, low cost and low power consumption high-performance computing (HPC) in practical use of neural network (NN), this paper presents a conceptual design study of dedicated computer for the NN processing. Then, dataflow architecture is adopted to develop the dedicated computer to be extremely high-performance by highly parallel processing. The topology of the NN and signal flow in the forward process are suitable for hardware acceleration, and it seems to readily construct the hardware circuit of the NN. In particular, dataflow architecture hardware circuits for both of the forward process and backward propagation process are considered in this work.

This paper presents a numerical investigation of the thermal interruption capability for the gas circuit breaker (GCB) adopting CO2/O2 mixture. The ohmic loss of the insulation gas is calculated from current continuity equation, and is utilized as a heat source for thermal fluid analysis. In order to accurately estimate the thermal interruption capability of a GCB adopting CO2/O2 mixture, we proposed an electric arc plasma model combining electric model and thermal fluid dynamics model. The validity of the proposed electric arc plasma model is verified by comparing it with experimental data. Subsequently, interruption indices are predicted using the calculated parameters to estimate the thermal interruption capability.

A surface integral equation method for modeling inductors in a wide frequency range is presented.

The unknowns are surface current and surface charge densities on the conductor surfaces. In the dielectric medium, a full-wave formulation is used, whereas in the conductor, a magneto-quasistatic model is considered. The full-wave formulation ensures that the model correctly takes into account high-frequency effects, such as resonance or radiation. The magneto-quasistatic model within the conductor yields accurate results for the real part of the impedance, i.e., the ohmic loss, starting from very small frequencies, where the 0th order surface impedance boundary condition is no longer valid due to the large skin-depth.