光伏系统用于漏电流测量的霍尔闭环传感器设计

基于闭环磁通门技术的传感器广泛应用在测量大电流中的小剩余电流以及噪声共模电流。这类传感器的精度以及对大电流的隔离能力使之成为漏电流检测的最优方案,但通常缺点是成本昂贵且体积庞大。本文介绍了一种新型小尺寸且利用霍尔闭环技术对太阳能系统中的漏电流进行测量的传感器:新一代的LDSR产品。     

Effect of multi pulse current treatment on microstructure and microhardness of resistance spot welded dual phase steel DP590

In this paper, microhardness and microstructural characteristics of dual phase DP590 steel resistance spot weld joint under two different welding conditions (i. e. single pulse and multi pulse) were studied. It was observed that applying multi pulse currents resulted in quasi-equiaxed grains of tempered martensite in fusion zone (FZ) of the weldment. The refinement of microstructure in fusion zone using multi pulse current treatment resulted in reduced hardness of the weld joint.     

电流驰豫法测试氧化镧掺杂的氧化铈中氧离子迁移

采用甘氨酸-硝酸盐法(GNP)合成了Ce0.65La0.35O1.825(LDC)粉末,在1400℃下烧结10 h得到陶瓷试样,用XRD和SEM表征了样品的物相和表面形貌。用直流电场测试了试样在不同温度下的电流驰豫现象,并计算了不同温度下试样中迁移氧离子数目和材料直流电导率。结果表明,在固态电解质材料中突然施加强电场,可迁移离子基本都发生了位置偏移,但极少部分可以产生长程迁移。随着温度的升高,样品中发生迁移的氧离子数目增加,但都远小于氧空位总量。迁移氧离子数目与温度之间满足阿累尼乌斯公式,其迁移活化能为0.83 eV。     

Improvement of surge current performances of ZnO varistor ceramics via C3N4-doping

ZnO-Bi₂O₃ based varistor ceramics doped with C₃N₄ were fabricated via solid state method. Experimental results show that C₃N₄ additive acts as an inhibitor in ZnO grain growth, and the average grain size decreases from 10.2–7.1 μm. The varistor breakdown voltage gradient increases from 222.3–282.3 V/mm, and the nonlinear coefficient increases from 51.9–58.2 with the increase of C₃N₄ content from 0 to 3.0 wt%. The C₃N₄-added samples exhibited smaller residual voltage ratio and better surge current withstanding capability. It is proposed that the C₃N₄-doping leads to substitution of nitrogen for oxygen in the grain boundary region, forming acceptor type defects. The acceptor type defects act as electron traps, increasing the barrier height from 1.31 to 1.50 eV and the depletion layer width from 54.9–61.8 nm, which increases the nonlinearity, and the surge current performances of the C₃N₄ doped ZnO varistor ceramics are improved.     

Constructing the high-areal-capacity,solid-state Li polymer battery via the multiscale ion transport pathway design

The parasitic Li dendrite formation and retarded ion diffusion dynamics inhibit the deployment of solid-state batteries (SSBs) at high areal capacity loadings. Here, we present the modular design of the Li⁺ percolating network by grafting the ionic-conductive polyether amine (PEA) at the multiple scales: the PEA modified zinc hydroxystannate (PEA@ZHS) (flame retardant units) and polyamide 6 (mechanical rigid units) are coherently introduced to optimize the PEO-based solid electrolyte (PX-PEA@ZHS) with the Young's modulus (3.41 GPa), ionic conductivity (4.29 × 10⁻⁴ S cm⁻¹ at 55 °C) and flame retardancy (22% reduction of heat release rate); on the other hand, PEA molecules are grafted onto the acetylene black additive to establish the dual conductive network, endowing two orders of magnitude increase of ionic conductivity for the high-compaction cathodes. The as-integrated symmetric cell exhibits a critical current density up to 0.8 mA cm⁻² and cycling endurance for 1000 h at 0.2 mA cm⁻²; upon the SSBs assembly with the record high loading of LiFePO₄ (12.4 mg cm⁻²), the high-areal-capacity, cycling stability as well as the extreme temperature endurance till 110 °C are simultaneously realized, which inspire the rational design of commercially feasible, energy-dense, flame-resistance energy storage prototype.     

Eddy Current Detection of Retained Austenite in Ni-Hard4 Cast Iron

In this article, the nondestructive eddy current (EC) method was used for microstructural evaluation of Ni-hard4 cast iron (NiHCI). Different destabilizing heat treatments were used to produce different microstructures and hardness. The microstructural analysis and hardness measurement were done for conventional characterization of the reference blocks. Then, the EC techniques were applied to evaluate the hardness and microstructural changes by the detection of EC parameters at different frequencies. Metallurgical investigations showed that increasing the destabilizing soaking time and temperature decreases the amount of retained austenite in NiHCIs. The nondestructive evaluation method (NDT) revealed that it can be good correlated between retained austenite amount and hardness with EC parameters. This shows that the EC technique can detect NiHCIs products according to the metallurgical characterization with good accuracy.     

Identification of factors that accelerate hydrogen production by Clostridium butyricum RAK25832 using casamino acids as a nitrogen source

The ability of Clostridium butyricum RAK25832 to use casamino acids as a nitrogen source was investigated. Strain RAK25832 showed the capacity to utilize different types of carbon sources. With glucose as a carbon source (10 g/L), the preferred final concentration of casamino acids was 26.67 g/L, with a cumulative hydrogen production, production rate, and yield of 2505 mL H₂/L, 160 mL/h, and 1.81 mol H₂/mol glucose, respectively. Eighteen metal elements were screened to identify the most important metals for biohydrogen production, and four elements were optimized. The optimal medium composition was MgCl₂·6H₂O (0.1 g/L), K₂HPO₄·3H₂O (6.67 g/L), NaHCO₃ (2.6 g/L), and FeCl₂·4H₂O (0.002 g/L). Vitamin supplementation of the medium showed no significant effect on hydrogen production. Under the optimized conditions, cumulative hydrogen production reached 3074 mL H₂/L. This is the first study to demonstrate the use of casamino acids as a nitrogen source by C. butyricum.     

Facile preparation of ultra-low Pt loading graphene-immobilized electrode for methanol oxidation reaction

Pulse current electrodeposition (PCE) technique was used to prepare graphene-supported platinum nanoparticles (GN-PtNPs) electrodes for the methanol electro-oxidation reaction in acidic media. The influences of the PCE parameters (applied current density, concentration of the Pt precursor, and duty cycle) upon the as-prepared GN-PtNPs electrodes for the methanol oxidation reaction (MOR) in terms of catalytic activity and tolerance against poisoning were studied using the Taguchi design of experiment (DOE). The analysis of variance (ANOVA) and signal-to-noise (S/N) ratio analysis provided prediction of optimal electrodeposition conditions to yield GN-PtNPs electrode which give the best MOR performance. The values of confirmatory experiment were demonstrated close to the values predicted using the Taguchi method. Transmission electron microscopy images showed that the Pt crystallites in flower-like structure were deposited evenly on the surface of graphene sheet. The Pt crystallites were predominantly in a zero-valent, metallic Pt state based on the X-ray photoelectron spectroscopy analysis.     

Direct model-based predictive control scheme without cost function for voltage source inverters with reduced common-mode voltage

This paper presents a direct model-based predictive control scheme for voltage source inverters (VSIs) with reduced common-mode voltages (CMVs). The developed method directly finds optimal vectors without using repetitive calculation of a cost function. To adjust output currents with the CMVs in the range of –V_dc/6 to +V_dc/6, the developed method uses voltage vectors, as finite control resources, excluding zero voltage vectors which produce the CMVs in the VSI within ±V_dc/2. In a model-based predictive control (MPC), not using zero voltage vectors increases the output current ripples and the current errors. To alleviate these problems, the developed method uses two non-zero voltage vectors in one sampling step. In addition, the voltage vectors scheduled to be used are directly selected at every sampling step once the developed method calculates the future reference voltage vector, saving the efforts of repeatedly calculating the cost function. And the two non-zero voltage vectors are optimally allocated to make the output current approach the reference current as close as possible. Thus, low CMV, rapid current-following capability and sufficient output current ripple performance are attained by the developed method. The results of a simulation and an experiment verify the effectiveness of the developed method.