交流电弧炉三相不平衡供电的研究

提出了三相操作电抗随无量纲电流变化的三相交流电弧炉电路模型,进而给出了适用于三相电流不对称,电压不对称和阻抗不对称情况的计算模型。基于上述三相交流电弧炉电路模型,分析了电流不对称和阻抗不对称对电弧功率的影响,并讨论了交流电弧炉三相电参数互相影响的复杂性。依据本模型可灵活实现三相交流电弧炉的平衡和不平衡供电,进而改善电弧炉的电气运行特性。     

双频淬火机床工频电源的理论分析

对工频电源主电路,在规定的满足平衡的条件下进行了计算,做出电流、电压的向量图。利用余弦定律计算出线电流及相角差,并画出了平衡时的三相供电网络的向量图,计算出平衡后的三相线电流相等。其电流的大小等于工件相电流的1／3倍,即单相负载的功率等于三相供电网络的总功率,解决了单相大负载用三相供电引起的三相电流不平衡问题。     

炼钢电弧炉炉内温度分布规律的研究

通过对大连钢厂30t电弧炉炉衬内表面温度的测定、分析与讨论,得出如下结论:1)电弧炉内,炉衬内表面温度分布不均衡,它与三相电弧功率不平衡度有对应关系。在试验条件下,测点中的最高温度为1596℃(5号点),三个“准热点”温度差异最高达12.4％,冷、热点的温度差为160～300℃,炉衬上、下温度梯度为0.29～0.61℃/mm。2)三相电弧功率不平衡度除与短网阻抗不平衡度有一定关系外,还受供电制度的影响。当二次电压提高时,电弧功率不平衡度变小;二次电流增加时,该值增大。3)电弧炉采用长电弧辅以泡沫渣保护的操作,对实现经济用电与获得好的炉内热工状况是有利的。     

LH-02小电流接地选线装置的研制

１引言在我国电力系统配电网中，由于还不能达到多电源供电，多数配电网和大型工矿企业的供电系统均采用中性点不接地或经消弧线圈接地的运行方式，即小电流接地系统。在中性点不接地系统中，正常情况下，系统三相电压对称平衡，三相对地电容相等。当发生单相接地时，PT开口三角绕组的电压升高３倍，故障线路的零序电流等于所有非故障零序电流之和，且方向相反，零序电流的大小与线路长度有关。根据这一特点，通过分析基波的幅值和相位，很容易找到接地故障线路。如过去的ML系列小电流选线装置，就是采用这一原理。而在中性点经消弧线圈接…     

电极电流交互作用对高硅合金生产过程影响的分析

高硅合金生产过程中,大型矿热炉的电极电流交互作用明显,引起了三相电极电流变化的不可预测性,同时由于大型矿热炉电抗值较高,引起了电极移动的不敏感性,频繁移动电极对电炉的三相电极功率平衡控制带来了一定困难。文章根据矿热炉电路原理对减弱电极电流交互作用和平衡三相电极功率提出了保持三相功率平衡的控制策略和措施。     

直流电弧炉的优越性

直流电弧炉的良好性能:电弧燃烧稳定,炉风热场均匀,引起的电压闪变水平较低,直流电弧电流对钢液的强力搅拌作用,良好的升温速度,电网的三相对称负荷,电极消耗较低等等。     

负载不平衡诱发的电压畸变

380／220状三相四线供电线路是生产生活中应用最广泛的电路．它不论三相负载是否平衡对称都能供电，给照明及单相电器用户带来极大的方便。但是这种方便也是有限度的，当三相负载不平衡达到一定程度时，负载端电压就会出现超越电压规定标准的畸变。     

三相异步电动机安全运行要领

简单介绍了三相异步电动机的原理，选用以及运行中的雏护与保养，重点阐述了三相异步电动机的常见故障及分析，保证电动机的安全运行。三相异步电动机是由定子上的对称三相绕组中通以对称三相交流电流所产生的磁势建立旋转磁场，而旋转磁场与由该旋转磁场在转子绕组内所感应的电流相互作用，产生电磁转矩来实现旋转运动，从而将电能转换为机械能。由于三相异步电动机具有结构简单、牢固耐用、启动容易、维护方便以及价格低廉等一系列优点，所以在工农业生产和生活各方面都得到了广泛应用。为了保证三相异步电动机的安全运行，电气工作人员必须熟练掌握有关三相异步电动机的安全运行的基本要领，了解对三相异步电动机的安全评估，做到尽可能地及时发现和消除电动机的事故隐患，保证安全生产。     

高电压高电抗AC电弧炉的电气设计

熔炼废钢的电弧炉的电弧电压较大地受到电弧无规则波动的影响,这对电弧炉的运行产生了不利影响。电弧波动不但使电弧炉熔化功率降低,还对供电电网产生干扰,在大电流系统中引起电机械应力。理论计算、模型模拟和从炼钢炉记录到的数据都表明,提高短路电抗能减小电压波动的负面影响。只有提高电弧炉变压器电压才能补偿高短路电抗引起的较高的压降。     

电弧炉电热特性及理论分析

讨论了电极向电弧炉中废钢等物料进行交流供电时,电弧连续燃弧的瞬时电流变化和功率变化规律;提出了合理的供电制度和电弧炉的供电设备的基本组成与要求.     

单电极直流矿热炉的偏弧分析

针对６．３ＭＶＡ直流矿热炉在冶炼硅铁时电弧偏移的现象,通过对三维磁场的计算,指出电弧偏移是由于炉外短网铜排中流过的强大直流所产生的磁场对电弧施加力的作用而造成的,讨论了炉外短网铜排对称布线方式对电弧偏移大小的影响及其抑制偏弧的效果。     

Liquid Metal Pool Behavior during the Vacuum Arc Remelting of INCONEL 718

Non-steady-state ensemble arc behavior has been observed during the Vacuum Arc Remelting (VAR) of 508-mm-diameter ingots of INCONEL 718. The liquid metal flow in the melt pool of a 508-mm ingot during VAR has been simulated under two alternative sets of conditions: (1) a steady-state axisymmetrical arc distribution, as has been typically used in modeling work previously; and (b) a transient asymmetrical arc distribution. Due to the computational requirements, neither mass flux nor solidification were modeled; instead, the pool shape was fixed from measurements from a 508-mm-diameter ingot, and a constant pool wall temperature of 1609 K was used. The transient simulation assumed a localized Gaussian arc whose effective center was located at a distance of 0.1 m from the ingot centerline; this simulation rotated clockwise around the centerline with a period of 36 seconds. The steady-state model was simulated with axisymmetrical distributions of current and power input to the pool top surface calculated by time averaging the transient current and power inputs. The standard k-ε solver of ANSYS CFX 5.6 software was used for both simulations. The transient model results suggest that 5 seconds of asymmetrical arc behavior is enough to change the pool from steady state to transient and that, after 30 seconds, the flow is almost fully developed (at least to the accuracy of the model) and dominated by the Lorentz force. Aspects of the model results agree with key features of the melt pool observed during VAR.     

Graft decentration in penetrating keratoplasty: nonmechanical trephination with the excimer laser (193 nm) versus the motor trephine

Seven right-handed participants performed bimanual circling movements in either a symmetrical or an asymmetrical coordination mode. Movements were paced with an auditory metronome at predetermined frequencies corresponding to transition frequency, where asymmetrical patterns became unstable, or at two-thirds transition frequency where both symmetrical and asymmetrical patterns were stable. The pacing tones were presented in either a high (1000 Hz) or low (500 Hz) pitch, and the percentage of high-pitched tones during a 20 s trial varied between 0% and 70%. Participants were instructed to count the number of high-pitched pacing tones that occurred during a trial of bimanual circling. Overall, the symmetrical pattern was more stable than the asymmetrical pattern at both frequencies. Errors on the tone-counting task were significantly higher during asymmetrical circling than symmetrical circling but only at the transition movement frequency. The results suggest that cognitive processes play a role in maintaining coordination patterns within regions of instability.     

直流埋弧炉的运行优势

目前已有的交流埋弧炉，由于载流导体存在着电感、集肤效应、干扰效应等诸多问题，造成功率因数非常低。若要向超大型化发展，受到了限制；若采用直流电源，这些问题便迎刃而解。本文论述了直流埋弧炉的运行优势及发展趋向。     

垃圾焚烧灰电弧熔融炉热工特性的研究

利用处理量为2 kg的直流电弧炉对医疗垃圾焚烧灰进行熔融实验研究。考察了电弧长度对弧电压、弧电流、熔池直径、熔融时间和电能单耗的影响。结果表明:随着弧长增大,弧电压呈近似线性增长,弧电流下降,熔池直径增大,熔融时间缩短,电能单耗降低。因此,在保证电弧稳定的前提下,应尽量采用长弧操作;与单独底灰熔融相比,飞灰/底灰混合熔融时的最大弧长较大,电能单耗较低;不足之处在于石墨电极单耗稍大。     

The Role of Side Arcing in the Global Energy Partition during Vacuum Arc Remelting of INCONEL 718

Non-steady-state ensemble arc behavior has been observed during the Vacuum Arc Remelting (VAR) of 508-mm-diameter ingots of INCONEL 718. The liquid metal flow in the melt pool of a 508-mm ingot during VAR has been simulated under two alternative sets of conditions: (1) a steady-state axisymmetrical arc distribution, as has been typically used in modeling work previously; and (b) a transient asymmetrical arc distribution. Due to the computational requirements, neither mass flux nor solidification were modeled; instead, the pool shape was fixed from measurements from a 508-mm-diameter ingot, and a constant pool wall temperature of 1609 K was used. The transient simulation assumed a localized Gaussian arc whose effective center was located at a distance of 0.1 m from the ingot centerline; this simulation rotated clockwise around the centerline with a period of 36 seconds. The steady-state model was simulated with axisymmetrical distributions of current and power input to the pool top surface calculated by time averaging the transient current and power inputs. The standard k-ε solver of ANSYS CFX 5.6 software was used for both simulations. The transient model results suggest that 5 seconds of asymmetrical arc behavior is enough to change the pool from steady state to transient and that, after 30 seconds, the flow is almost fully developed (at least to the accuracy of the model) and dominated by the Lorentz force. Aspects of the model results agree with key features of the melt pool observed during VAR. This article is based on a presentation given at the International Symposium on Liquid Metal Processing and Casting (LMPC 2007), which occurred in September 2007 in Nancy, France.

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Perception of symmetry in infancy.

Symmetrical visual patterns, particularly vertically symmetrical ones, are preferred and processed faster than asymmetrical patterns by adults. Results of 3 experiments with 61 4- and 12-mo-olds show that (a) 4-mo-old infants showed no preference for symmetry, but they processed vertically symmetrical patterns more efficiently than horizontally symmetrical or asymmetrical ones; and (b) by 12 mo, infants preferred vertical symmetry to horizontal symmetry and asymmetry. Thus, preference for symmetry seems to develop late, whereas recognition of vertical symmetry is innate, matures very quickly, or is learned very early. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

衡管90 t超高功率交流电弧炉设计特点分析

较详细阐述了衡管90 t电弧炉的主要设计特点：即变压器容量70 000 kVA;电极直径560mm;采用静态无功补偿供电系统（SVC）、高阻抗操作以及碳氧喷枪和无渣出钢;冶炼周期58min;节能水冷板,设计达到国际最先进水平.     

一种新型整流电源在直流电弧炉上的应用——剖析法国CEGELEC用于直流电弧炉的新型整流电源

法国CEGELEC新近在新疆八一钢厂投产的70吨直流电弧炉采用了一种新型的整流电源,具有很好的研究和开发价值。这种系统是一种当今最新的控制技术且非常适合于中国电网条件差的情况。