非正弦不对称三相三线电路负载侧相电压的定义与测量

对非正弦不对称三相三线电路，如何恰当地定义负载侧的相电压并能方便地测量一直未有明确的统一认识。本文从研究三相三线电路中相电压与线电压的关系着手，根据外部等效的思想。来定义三相三线电路负载侧的相电压。按此定义的相电压恒满足ｕ，＋“ｂ＋“ｃ＝０，并可方便地通过三相电压互感器或直接依据负载侧的线电压来唯一确定负载侧的相电压。     

大型氢冷汽轮发电机氢油水集散控制系统

近年来，集散控制系统在国内外电站已被逐步认识，推广和应用。本叙述了ＤＣＳ如何在大型氢冷汽轮发电机氢油水控制系统上的应用，并对其原理，设计方案软硬件的选择进行了分析和阐述。     

Hochdynamische Leistungsregelung eines dreiphasigen Hochleistungs-netzstromrichters zur Speisung von Gleichspannungszwischenkreisen

Übersicht In dieser Arbeit wird ein neues Regelungsverfahren für U-Netzstromrichter sehr hoher Leistung beschrieben. Die Einspeisungsschaltung besteht aus zwei GTO-Dreipunktstromrichtern, die über Dreiwicklungstransformatoren mit in Stern bzw. Dreieck geschalteten Sekundärwicklungen ans Netz geschaltet sind. Für den Betrieb als Netzstromrichter wird eine Steuerstrategie entwickelt, wobei eine möglichst geringe Verzerrung der netzseitigen Spannung unter Einhaltung der geringen zulässigen Schaltfrequenz der Ventile das Ziel ist. Die Regelung für netzfreundlichen hochdynamischen Energieaustausch zwischen Netz und Zwischenkreis ist auf der Basis der sogenannten Stromrichterflußbahn konzipiert.

---

Highly dynamic control for a three-phase high power AC/DC converter

Contents This paper describes the implementation of a new control approach for a high power three-phase AC/DC converter. The converter consists of two three-level inverters connected to the line via a three-winding transformer with the secondaries connected in star and delta. The control scheme is developed to minimise the network distortion voltage while keeping the small permitted switching frequency of the valves. The control for highly dynamic exchange of energy between the network and the dc link voltage is proposed on the basis of the converter voltage space vector time integral.

---

---

Diese Arbeit wurde von der Deutschen Forschungsgemeinschaft gefördert.     

Dielectric breakdown of a residual SF6 plasma at 3000 Kunder diatomic equilibrium

A residual plasma at 3000 K and under diatomic equilibrium is left inside an axially blown gas blast SF₆ circuit breaker after the thermal extinction of an arc. The breakdown of such a residual plasma depends on the electron generation and loss mechanisms. Altogether six ionization and chemical reactions relevant to the time scale of breakdown have been taken into account. It has been found that the critical field strength for breakdown is proportional to the pressure and is equal to 2.0 V/(m.Pa). This field strength is in agreement with the experimental results     

Advances in selective wet oxidation of AlGaAs alloys

We review the chemistry, microstructure, and processing of buried oxides converted from AlGaAs layers using wet oxidation. Hydrogen is shown to have a central role in the oxidation reaction as the oxidizing agent and to reduce the intermediate predict As₂O₃ to As. The stable oxide is amorphous (Al_xGa_1-x) ₂O₃ which has no defects along the oxide/semiconductor interfaces but can exhibit strain at the oxide terminus due to volume shrinkage. The influence of gas flow, gas composition, temperature, Al-content, and layer thickness on the oxidation rate are characterized to establish a reproducible process. Linear oxidation rates with Arrhenius activation energies which strongly depend upon AlAs mole fraction are found. The latter produces strong oxidation selectivity between AlGaAs layers with slightly differing Al-content. Oxidation selectivity to thickness is also shown for layer thickness <60 nm. Differences between the properties of buried oxides converted from AlGaAs and AlAs layers and the impact on selectively oxidized vertical cavity laser lifetime are reported     

Tapered rib adiabatic following fiber couplers in etched GaAsmaterials for monolithic spot-size transformation

Design details and demonstration data are presented for an (Al,Ga)As monolithic tapered rib waveguide achieving modal spot-size transformation. The tapered rib adiabatic following fiber coupler structure (TRAFFIC) achieves two-dimensional (2-D) expansion of the output optical mode of single-transverse-mode semiconductor waveguide modulators and lasers using a one-dimensional (1-D) taper between noncritical initial and final taper widths which are compatible with optical lithographic techniques. Measurements are presented of total mode expansion losses between ~1.5-2.0 dB and semiconductor to single-mode-fiber waveguide coupling losses of ~0.5-1.0 dB for doped pin optical-modulator-type waveguides using the TRAFFIC waveguide. A semiconductor laser with a TRAFFIC tapered-rib mode-expansion section and measured coupling loss between the laser output and single-mode fiber of only 0.9 dB is described. Finally, a TRAFFIC Spot-size transformer for undoped waveguide modulators with total mode expansion losses of 1.84 dB and excellent modal behavior at 1.32-μm wavelength is presented. The TRAFFiC structure is particularly well suited for integration with both active and passive etched rib waveguide devices. Fabrication is relatively simple, requiring only patterning and etching of the tapered waveguide and uniform-width outer mesa waveguide without any epitaxial regrowth     

大中型商场空调系统的节能设计

本文分析了商场夏季提高室内设计温度的节能问题；介绍了回收排风能量的换热器与空调机组合的形式、设计特点、经济效益；提出了一种利用商场排风充当风冷热泵机部分进风而节能的新方式。     

厨房煤气燃烧对室内空气中氮氧化物浓度的影响

为进一步了解燃气排放污染物造成的室内氮氧化物污染状况,对北京东郊使用管道煤气为炊用燃料的居民住宅室内空气中的氮氧化物进行了监测,分析了由于炊用煤气燃烧造成的氮氧化物的污染状况和影响因素.同时,对室内换气率、机械抽排作用等因素进行了研究,并讨论了单室模型描述燃气燃烧造成厨房空气污染的适用性.     

H13钢的退火软化

应用Ｆｆｏｒｍａｓｔｅｒ－Ｄｉｇｉｔａｌ全自动相变仪测定了Ｈ１３钢的退火用ＴＴＴ图，利用物理化学相分析法，扫描电镜分析，Ｘ射线衍射分析，测定研究了Ｈ１３钢不同退火工艺处理后钢的基体中合金元素含量，碳化物类型，尺寸，分布和相对数量，测量钢的退火硬度，分析了硬度与碳化物粒子大小，相对数量，碳化物结构类型的依赖关系。     

气敏元件测量电路的一组优化设计

本文研究了气敏元件测量电路的一组优化设计，主要有线性升压加热源、元件电阻输出比例器、声光提示及自动回零电路等九部分。利用这组优化测试电路可直接绘出气敏元件电阻随国热电压变化的连续曲线，灵敏度精确值以及选择特性。它对气敏元件的特性研究和制作都是很有价值的。