DETECTION AND ANALYSIS OF WELD POOL SHAPE FOR CO_2 SHORT CIRCUITING ARC WELDING

A general industrial CCD( ICCD) camera is redesigned to detect the weld pool without arc at the period of short circuiting, so that the interference of arc and spatter during CO2 short circuiting arc welding is eliminated. Through the analysis of weld pool image, both size parameters (such as weld pool area A, weld pool length L1, L2 and weld pool breadth b) and contour parameters (b, which describe the curves of weld pool boundany) ,which could indicate the shape features of weld pool, had been defined to express weld pool information quantitatively. The investigation of the relationships between weld pool shape parameters and welding process parameters may be beneficial to the quality control of CO2 welding.

Study on chaos in short circuit gas metal arc welding process

Based on the chaos theory, an idea is put forward to analyze the short circuit Gas Metal Arc Welding （ GMAW-S） process. The theory of phase space reconstruction and related algorithms such as mutual information and so on, are applied to analyze the chaos of the GMAW-S process. The largest Lyapunov exponents of some current time series are calculated, and the results indicate that chaos exists in the GMAW-S process. The research of the chaos in the GMAW-S process can be help to get new knowledge of the process.

Short-circuit process model in underwater welding using rotating arc sensor

In order to detecting and tracking along the weld seam with rotating arc sensor in underwater welding,the highpressure water environment rotating arc welding hardware platform is established and welding experiments using rotating arc sensor is done. Different radius of rotating arc sensor is used. And the corresponding welding current and voltage is obtained,which is compared with the results of rotating arc sensor short-circuit process simulation model under high-pressure water environment established in this article. The results show that under high-pressure water environment,rotating arc radius should be optimized,otherwise the short-circuit-arcing cycle will transit to a short-circuit-arcing-abruption cycle,making the welding quality poor. At last the critical radius between the short-circuit-arcing cycle and short-circuit-arcing-abruption cycle under high-pressure water environment is obtained.

Effects of current waveform parameters during droplet transfer on spatter in high speed waveform controlled Short-circuiting GMAW

Aim at improving the stability of the Short-circuiting Gas Metal Arc Welding （GMAW-S） process for the enhanced speed usage, effects of current waveform parameters during short-term on the welding stability have been investigated by experimental method. The welding power source used for the research is an inverter with a special current waveform control. It is shown that the spatter decreases at first then increases with each increase of the low current period, current increase rate and the maximum current limit. The test results are provided for welding of 1 mm and 3 mm mild steel at speed of 1.2 m/min. The stable GMA W-S process under high speed welding condition has been achieved by optimizing the parameters.

Effect of welding speed and electrode extension on the approximate entropy of welding current in short-circuiting GMAW

Based on the phase space reconstruction of welding current in short-circuiting transfer arc welding under carbon dioxide, the approximate entropy of welding current and its standard deviation have been calculated and analyzed at different welding speeds and different electrode extensions respectively. The experimental and calculated results show that at a certain arc voltage, wire feeding rate and gas flow rate, welding speed and electrode extension have significant effects not only on the approximate entropy of welding current, but also on the stability of welding process. Further analysis proves that when the welding speed and electrode extension are in an appropriate range respectively, the welding current approximate entropy attains maximum and its standard deviation minimum. Just under such circumstances, the welding process is in the most stable state.

A new simulation model and its application in CO_2 short-circuiting transfer welding

A new simulation model of CO 2 short circuiting transfer welding may be employed to develop a new pattern of welding machine and to predict welding process parameters to obtain the optimum welding technology properties. In this paper, a new simulating model is developed according to the AWP (adapting welding physics process) waveform control method. Good agreement is shown between the predicted and experimentally determined results. The model will make an important promotion in the development of CO 2 arc welding technique.

Process disturbances monitoring and recognition of short-circuiting GMAW by fuzzy c-means system

An intelligent fuzzy c-means system for process monitoring and recognition of process disturbances during short- circuiting gas metal arc welding （GMAW） is introduced in this paper. The raw measured and statistically test data of probability density distribution （ PDD ） and class frequency distribution （ CFD ） of welding electrical parameters are further processed into a 7-dimensional array which is designed to describe various welding conditions, and is employed as input vector of the intelligent fuzzy c-means system. The fuzzy c-means system is used to conduct process monitoring and automatic recognition. The correct recognition rate of 24 test data under 8 kinds of welding condition is 92%.

变压器内部电弧故障快速检测方法研究与对比

变压器内部短路电弧故障是变压器最危险、最严重的故障,极有可能造成变压器油箱的形变和破裂,乃至变压器油的燃烧与爆炸,对人员生命安全、变电站财产安全、电网运行安全都造成了严重威胁。实现变压器内部短路电弧故障的快速检测有利于及时发出断路器分闸信号,从而缩短电弧燃弧时间,减小电弧能量,降低燃爆可能性。为寻找适用于电弧故障快速检测的信号及特征,首先搭建了基于电容电感串联谐振的油中工频大电流电弧实验平台,并实现了油中工频电弧的电压、电流、压力波、光、电磁脉冲、气泡形态等关键电弧特性的测量;发现压力波存在前期快速振荡-后期持续上升两阶段,光信号存在间隔约10 ms的脉冲,电弧电流过零点时必定会产生电磁脉冲,上述压力波、光和电磁脉冲3种信号及其特性有望应用于变压器内部短路电弧故障的快速检测;最后对比了这3种故障检测方法的优缺点,并指出这些方法在工程实际应用前急需进一步解决的问题。

特高压换流变压器匝间短路故障建模与仿真

近年来,特高压换流变压器内部短路故障导致的爆炸起火事故接连发生,严重威胁电力系统安全稳定运行。本文以±800 kV特高压换流站典型单相四柱式换流变压器为研究对象,基于ANSYS Maxwell和Simplorer平台开展绕组匝间短路故障建模仿真,研究不同故障条件下绕组漏磁、短路环流及电弧故障能量的变化规律。结果表明:伴随匝间短路发生,换流变压器内部大量横向漏磁破坏绕组正常纵向磁通分布,短路匝环中出现高幅值故障环流。1.98%匝间短路漏磁峰值达2.76 T,短路环流峰值达80.59 kA,四个周波内释放能量1.22 MJ。根据安匝平衡规律,短路匝数越多,环流幅值越小,而电弧电压随电弧长度单调增加,总体而言电弧能量与短路匝数呈正相关。此外,由于漏磁畸变引起的漏电感差异,靠近绕组中部的匝间短路故障更为严重。

GIS设备短路电弧效应与压力释放装置设计

分析了GIS设备内部短路电弧造成的问题,介绍了GIS设备异常时气室压力上升和外壳烧穿时间的计算方法,并初步探查了GIS设备壳体的有效防护措施——压力释放装置的合理设计。同时,以某种550kVGIS设备为例,计算短路电弧出现时气室内部压力变化及壳体烧穿时间,结果表明各气室的壳体设计均满足要求,没有发生壳体烧穿、破裂的可能性。

船舶中压配电板可触及性问题分析与处理

基于某大型工程船建造和检验过程中发现的中压配电板可触及性问题,阐述中压配电板内部故障电弧等级和短路燃弧试验标准、燃弧试验达标的判据。通过对燃弧试验报告的详细分析,从多个方面确定可触及性等级差异的缘由,提出了以整体式壁板分隔背面区域、以局部防护板分隔泄压区域、优化天花板的设计以隔离泄压区域等三种处理方案,分析比较各自的可行性和优缺点,综合决策确定处理方案。

微型断路器灭弧系统对短路分断能力影响的研究

短路分断能力是微型断路器(MCB)的一项重要的技术指标,影响该指标的因素很多。通过对分断试验样机烧蚀的情况——动触头引弧板顶部电弧停滞时间长、烧蚀严重及灭弧栅片未被有效利用进行分析,结合理论提出优化方案并进行试验验证,得出优化引弧板设计、灭弧室设计以及出气口结构有利于缩短电弧停滞时间,加快电弧的引弧速度,提高栅片切弧利用率,以增加电弧电压,进而提高MCB的分断性能。

基于电流转移的断路器弧后电流测量方法

断路器的弧后电流是断路器开断性能的重要参量,为了获取高精度、低干扰的弧后电流,本文提出了一种基于真空开关、转移电阻、保护间隙和高精度电流传感器构成的弧后电流测量方法,其中真空开关负责导通大电流,在电流过零前电流转移到转移电阻上,然后利用高精度电流传感器间接测量弧后电流。建立了弧后电流装置的电流转移过程模型,分析了电流转移完成时刻和转移电流峰值受转移电阻、电流大小和真空开关刚分时刻的影响。基于仿真得到弧后电流测量装置的参数,设计了弧后电流测量装置样机,对转移电阻进行了特殊无感设计并与保护间隙实现配合保护。最后进行了10 k V真空断路器在合成回路试验中的弧后电流测量,在开断5 k A电流时,弧后电流峰值为500 m A左右,脉宽5μs,弧后测量干扰小,波形平滑。对比试验结果和前人研究成果,验证了基于电流转移原理的弧后电流测量装置的可行性和准确性。

改进混合型限流断路器限流特性及换流电弧能量分析

混合型限流断路器兼备了机械开关良好的静态特性和固态开关无弧快速分断的动态特性,是国际上断路器研究的新方向。为了对高di/dt电流下混合型限流断路器的换流电弧能量进行分析,在已研制出的两种混合型限流断路器样机基础上,开展了相同实验线路参数和设定动作值条件下的两种限流断路器方案的对比实验。改进方案可将电流上升率di/dt为18A/μs的短路电流限制到7.5kA,分断动作时间1ms,相比于初始方案,改进方案分断速度更快,限流能力更强。进而计算了2种方案在不同短路电流上升率下的换流电弧能量,并分析了电弧能量对触头烧蚀特性的影响。改进方案能够有效地降低换流电弧能量,减小电弧对触头的烧蚀,提高触头寿命。研究表明改进方案更适合需要多次分断高di/dt短路电流的应用场合。

牵引供电新型异相短路保护原理的研究

在建立电弧模型的基础上,对异相电弧短路故障信号进行仿真分析,证明原有的馈线保护原理存在缺陷。对牵引供电系统异相电弧短路故障发生时,各相电压电流的谐波特点进行分析研究,提出了通过检测异相短路两供电臂间电压来确认异相短路发生时的低压保护方案。通过对轻、重载和单臂、双臂工况下发生异相电弧短路故障时的两供电臂间相间电压仿真,验证了该保护方案的正确性,有效性和可行性。这种保护方案可作为牵引网异相短路的主保护,并与牵引网馈线成套保护结合,组成牵引网完整的保护策略。

航天器供配电分系统电弧短路故障及其防护

介绍了航天器电弧故障的机理,给出了不同材料的真空电弧特性,总结了航天器太阳电池阵、太阳电池阵驱动机构(SADA)和母线三大类电弧故障模式,提出了太阳电池阵电弧故障的一般防护方法,并介绍了国际标准ISO11221-2011试验验证方法。建议深入开展相关故障机理与防护和验证新技术研究,建立相关产品保证规范体系,以防止航天器电弧短路故障发生。

CO_2气体保护焊短路过渡过程与电参数的关系

用计算机控制的高性能数据采集系统对 CO2 焊短路过渡过程的电参数进行了研究 .分析认为可利用电弧电压来指示熔滴短路及电弧复燃 ,利用电弧电压的微分来指示液体小桥缩颈 ,为 CO2 焊短路过渡实时控制奠定了基础 .

太阳电池有无减反射膜的短路光电流增量比上限

太阳电池覆盖各种减反射膜或作其它减反射表面处理后 ,其短路光电流密度的增量与有减反射膜的短路光电流密度的比 ΔJL/JL 小于或等于裸太阳电池表面加权平均反射率 Rω,即 ΔJL/JL Rω。

双丝间接电弧氩弧焊的熔滴过渡

采用氙灯背光高速摄像系统及示波器对双丝间接电弧氩气保护焊的熔滴过渡及其对应的电压、电流波形进行了研究。结果表明,双丝间接电弧氩弧焊焊接电流与电弧电压的不同匹配选择,熔滴具有短路过渡、大滴过渡、混合过渡、射滴过渡、射流过渡等不同过渡形式。随着焊接电流的增大熔滴尺寸减小,熔滴细化,随电弧电压的增大,熔滴尺寸减小。熔滴过渡形式与电压、电流的波形之间有很好的对应关系。

CO_2焊熔滴过渡特征的分析和研究

介绍了熔滴过渡的数据采集系统，采用多种数据处理方法对焊接电压波形和电流波形进行分析，并从中提取出短路过渡的熔滴过渡特征。重点阐述了各种方法的实现和应用效果。