Three‐Phase AC Filter Inductor Design for Three‐Phase PWM Inverter for Conversion Efficiency Improvement at Low Load

The inductor losses in a three‐phase ac filter inductor used in a three‐phase pulse‐width modulation (PWM) inverter are evaluated. First, a three‐phase inductor is designed to obtain the same value of inductance for each phase. Then, based on the design, a three‐phase inductor that uses two magnetic materials is proposed. The conversion efficiency of a 1 kVA three‐phase PWM inverter that uses the conventional and proposed ac filter inductors is simulated. Simulation results show that conversion efficiency improves. Finally, the conversion efficiency of an actual three‐phase 1 kVA PWM inverter that uses the conventional and proposed ac filter inductors is measured. In the experiment, the conversion efficiency obtained for the case of the proposed inductor improves by approximately 1% at low power load as compared to the conventional inductor. Furthermore, the calculated inductor losses are in good agreement with measured losses. Improvement in efficiency is verified trough simulations and experiments.     

非晶半导体的研究与应用

1968年Ovshinsky在多元硫系薄膜中观察到电的开关与存贮效应以来,特别是1975年氢化非晶Si的p型与n型掺杂控制的实现,非晶半导体作为一个重要的电子材料,在过去的30多年中吸引了大量的基础研究并得到了广泛的应用。本文综述了至今为止非晶半导体重要的研究与应用进展,并探讨非晶半导体今后主要的发展趋势。     

Effect of current density on Al alloy microplasma oxidation

The microplasma oxidation process of LY 12 Al alloy in Na2SiO3-KOH-NaAlO2 system has been studied. The voltage-time curve of oxidation process is changed with the variation of current densities. The voltage breakdown and hardness of coating increase with increasing current density. The phase composition, morphologies, element and the distribution of ceramic coating are investigated by XRD, EPMA.     

和线画匹配的阶调再现

目的为了探索和线画匹配的阶调再现。方法采用明暗描画的非真实感渲染方法将阶调再现这个反映输入明暗和打印出图像的浓度关系的画质因素导入到面积变调的线画中。结果建立了一套自动绘制线画的系统,并发现了和线画匹配的阶调再现。结论可以看出要表现深层的感受,即使是灰度值数值段很少的明暗阶调,选择合适的阶调再现也是非常重要的。     

Preparation of Transparent Egg White Gel with Salt by Two-step Heating Method

A heat-induced transparent gel from egg white was prepared at low pH and low ionic strength by a one-step heating method. The addition of NaCl to the egg white formed a turbid gel on heating. Egg white, first diluted with water, gave a transparent solution upon heating of this mixture. The solution formed a transparent gel when heated with NaCl up to a concentration of 0.3M for a second time. The transparent gel obtained at 150 mM NaCl was more firm and less adhesive than the turbid gel prepared by the one-step heating method at the same pH, protein concentration, and NaCl concentration.     

Experimental Services of Energy Management for Energy Users in Business Region on Miyakojima City All‐Islands EMS Demonstration Project

Smart grid and demand response (DR) had been attracting attention and evaluated in several demonstration projects. Many DR experimental results for residential and large‐scale buildings had been evaluated, while evaluation for small size buildings seems to be not enough. In this paper, a new energy service combined EMS method is proposed for small size buildings. Then results of its application to Miyako Island All‐Islands EMS Demonstration Project are introduced. The experimental services include not only DRs but also peak cutting recommendations and energy analysis reports. The results show combination of services can realize more effects than individual service. Especially the peak cutting recommendations and energy analysis reports help energy consumers to learn and understand how to save and manage energy usages that lead to effective DR potentials. Also the experimental system developed for energy data measurement and DR management as an island community EMS is intrduced.     

An automatic digital Q-meter for low values of Q

An automatic digital Q-meter suitable for measuring low Q-factors at low frequencies is described. It Uses a microcomputer. In a conventional digital Q-meter, the number of damped oscillations which occurs in the time interval between the initial peak and the damped peak exp (? n) times smaller than the first one, corresponds to the numerical value of the Q-factor. For small Q-factors a considerable error occurs in this procedure, and the error can be eliminated by the procedure presented in this paper.     

The Circuit Analysis and Performance Evaluation of an Hc Type Magnetic Coupling Contactless Power Transformer that is Compatible with Both Solenoid and Circular Type Transformers

There are two types of the transformers in a contactless power transfer system: solenoid type (H‐shaped) and circular type transformers. These two types of transformers are not compatible because their magnetic field structures are different. An Hc type transformer that is compatible with both transformer types has been proposed. The Hc type receiver adds a central magnetic pole by dividing the winding coil of the H‐shaped receiver. The Hc type receiver can change the magnetic field structure by changing the connections of the divided windings and can receive power from both types of transmitters. In this study, we conducted a circuit analysis and evaluated the performance of the Hc type transformer.     

A Urinary Bladder Volume Measurement Circuit Using a Simplified Very Small Phase Difference Measurement Circuit

In order to implement the measurement and the evaluation of analog signals in high accuracy, to detect not only amplitude level but also phase information is necessary. For example, measurement of very small phase difference is desired in fields such as electric power and organism‐related. Particularly, in organism‐related field, impedance measurement is important and it is used to measure the urinary bladder volume, the respiratory volume, and so on. For these purposes, portable and real‐time measurement devices with small sized is suitable. In this paper, we propose the urinary bladder volume measurement circuit using a simplified very small phase difference measurement circuit. This circuit is able to infer the changes of urinary bladder volume by measuring bioimpedance and phase difference of urinary bladder noninvasively with four‐terminal method.     

The Proposal of Isolated Single‐Stage AC‐DC Converter

An isolated ac‐dc converter has been used in various applications, such as power supply and as a battery charger for electric vehicle. In conventional converters, a loss in each conversion stage can be reduced by applying a soft switching method. However, a conventional converter has many conversion stages including the rectifier stage, power factor correction, and dc/dc converter stages; thus, it is difficult to reduce the total converter loss and size. In this paper, we propose a novel isolated‐type ac‐dc converter with only one conversion stage; it can realize a zero‐voltage switching operation in all switching devices.