IGBT逆变弧焊电源CO2气体保护焊飞溅的波形控制

随着逆变焊机的发展和数字技术的应用,逆变CO2气体保护焊电源可通过调节焊接电源输出的电流与电压来控制熔滴过渡,改善焊缝成形,降低飞溅.根据熔滴过渡不同阶段的要求产生电流与电压控制信号,进行波形控制可实现调节短路电流上升速度,以减小短路峰值电流,降低短路爆炸能量;减少瞬时短路的次数;通过短路后期液桥颈缩电压上升率切断短路电流,消除电爆炸能量.以此有效减少CO2气体保护焊短路过渡产生的飞溅量,为低飞溅CO2气体保护焊的设计与实现提供有力保证.     

新型逆变式CO_2气体保护焊机

CO_2焊是一种高效节能的焊接方法。该法中最常用的是短路过渡形式,这时的负载变化较大,所以对焊机的动特性也有严格要求。而逆变式焊机,由于工作频率较高,所以有较强的动态响应能力。同时,选择合适的电子电抗器,能获得与负载变化相适应的动特性。因此,采用逆变式CO_2焊机为获得低飞溅,良好的成形,较高的引派成功率及良好的收弧效果等优良性能提供了保证。该焊机一问世,必将推动CO_2焊接方法的加速推广。     

闭环霍尔电流传感器在逆变焊机中的应用

本文介绍闭环霍尔电流传感器的工作原理及在逆变焊机中的应用，实现了对逆变焊机输出电流的隔离测量、控制，解决了逆变焊机输出电流的限流保护问题。     

协同式CO2焊短路过渡模糊控制系统研究

介绍了一种在波形控制基础上,采用电弧自身传感的协同式模糊控制方法对焊接过程参数进行实时控制的逆变式CO2焊机控制系统.它通过电弧自身传感对CO2焊接过程有重要影响的短路过渡频率的检测,通过模糊处理和模糊判决之后,实时的对电弧电压进行控制,以保持焊接过程中规范参数的协同匹配关系.试验结果表明,采用该控制系统的焊机,实现了焊接规范参数的自动匹配和自动调节,同时明显改善了焊缝成形和降低了焊接过程中的飞溅.     

ZX71GBT高效节能型焊机

1993年我公司购置了ZX7 IGBT逆变式直流焊机,感觉其与其它焊机相比有无可比拟的节能效果和性能优势。 IGBT（Insulated Gate Bipolor Transistor）逆变式焊机为80年代发展起来的第六代焊机。其主要器件IGBT又称为绝缘栅型双极晶体管,它集中了场效应管开关频率高与晶体管通过电流能力强的优点,开关频率25Hz,开关速度1μs,额定电流密度100A／cm2,电压驱动自身损耗小,是目前最为先进的器件之一。其等值电路见图1。用它制造的焊机电源与过去的焊机相比,独具优势。指标比较见表1。 ZX7 IGBT逆变直流焊机的特点如下。 1． 体积…     

全数字化气体保护逆变焊机的设计与开发

利用逆变电源响应速度快、控制精度高、易于实现数字化控制的特点,设计了用于气体保护焊生产的全数字化逆变焊机。开展了可以满足CO2气体保护焊、直流MIG焊和脉冲MIG焊的微机控制多功能IGBT逆变焊机的研制,完成了包括主电路、控制电路、脉宽调制电路、驱动电路、系统软件设计以及焊机安装调试等多项任务。对焊机电源各组成部分进行了功能分析,并记录了试验数据与波形。试验表明:该焊机响应速度快,硬件电路简单可靠,抗干扰能力强,达到设计要求。     

高压线路并联电抗补偿特性及分析

随着电力系统的发展,装机容量的不断增加,高压输电线路电压等级不断提高,输电距离不断增加,从而引起电力系统电容电流以及容性无功功率的增长,导致电网电压偏高,分析了500kV输电系统并联电抗器的补偿特性,阐述了500kV并联电抗器开断的过电压及限制措施,并联电抗器对高压线路进行无功补偿的作用﹑意义,对电力系统的影响,以及并联电抗器的特性和作用。     

IGBT逆变弧焊机可靠性的探讨

本文就IGBT逆变焊机可靠性的问题进行了探讨。介绍了逆变主电路的设计及器件的选择对可靠性的影响；讨论了逆变焊机中过电压、过电流的保护电路。文中还就驱动电路的应用及控制电路的抗干扰问题进行了讨论。     

一种基于PIC系列单片机的SPWM逆变电源

叙述了一种基于PIC系列单片机设计的SPWM逆变电源.该电源以12V直流电压为输入.通过升压环节与SPWM逆变环节,得到了设定频率与电压的优质正弦交流电.应用开关电源的设计原理,在直流推挽升压模块中,采用了电压负反馈,使得升压后的高电压具有良好的稳定性;逆变部分采用单片机数字化SPWM控制方式,以尽可能地减少谐波.采用了基于单片机的数字化技术,使得电源调节灵活、性能可靠,为性能要求高的仪器设备提供了一种高品质的交流电源.     

高速列车用变极性焊接电源的研究

本文简要分析了几种二次逆变拓扑形式,提出了一种新的带有耦合电感的半桥逆变结构。此电路结构不需要附加其他的硬件引弧设备,利用产生的电压脉冲实现再引弧,通过适当的控制策略即可实现全电流范围的方波焊接。电路的电流换向时的引弧参数可以调节,可以使焊机在多种保护气体多种环境下做到最优化的引弧焊接。试验证明此换向拓扑结构电流换向速度快,焊接过程稳定,结构简单可靠,适于推广使用。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.