国内外电力电子器件发展现状

简要回顾了电力半导体器件的发展历史。对光控晶闸管(LTT)、集成门极换向晶闸管(IGCT)、绝缘栅双极晶体管(IGBT)以及反向开关两端晶闸管(RSD)等新型器件的工作原理、现状做了介绍。指出电力半导体是电力电子技术的基石．离开他们．电力电子技术将是无米之炊。     

Solidification behaviour and microstructure of welding transition zone using low-transformation-temperature welding consumables

The solidification behaviour and microstructure of welding transition zone between low-transformation-temperature deposited metals and high-strength low-alloy steels were investigated. It was found that the steep composition gradient provided driving forces for the diffusion of carbon from base metal to weld metal, leading to the hardened and softened regions near fusion boundary. In weld metal near fusion boundary, there were retained δ-ferrites when the base metal dilution rate below 35% and Cr_eq/Ni_eq value larger than 2.62. Compared with martensite, the mixed microstructures of martensite?+?δ-ferrite obtained less strain localisation, dislocation density and more percentages of large misorientation, which were more liable to resist microcrack initiation and propagation during deformation.     

CO2焊和MAG焊的工艺性能及焊丝的研发与应用

通过CO2气体保护焊和混合气体保护焊(MAG)工艺性能的对比,强调MAG焊在减少熔滴过渡过程中的飞溅、改善焊缝成型、提高焊缝金属冲击韧性方面优于CO2焊接工艺.列举了MAG焊在重要构件如管线钢管等焊接方面的应用实例,提出:对薄板及要求不高的构件可采用纯CO2焊;对中、厚板及对焊缝质量要求(如韧性、外观等)较高的重要构件,推荐采用纯CO2气体 药芯焊丝或富氩(Ar CO2)混合气体 实芯焊丝两种工艺;有条件的情况下应积极使用脉冲MAG电源,以进一步提高焊速,改善过渡.同时重点介绍了日本近年关于焊丝开发(无镀铜实芯焊丝、焊后去应力回火钢材用无再热裂纹全位置药芯焊丝、低相变温度焊丝)与应用方面的研究成果.     

Nutzung von Low‐Transformation‐Temperature‐Werkstoffen (LTT) zur Eigenspannungsreduzierung im Elektronenstrahlschweißprozess

Low‐Transformation‐Temperature materials (LTT) were designed to reduce delay as well as residual tensile stress in welds on carbon‐manganese steels. Using the volume expansion effect during a martensitic transformation these materials counteract the volume shrinkage during cooling. While this positive effects on residual stress relief by Low‐Transformation‐Temperature‐alloys has been proven in various studies, these alloys have always been used in large volumes as additional filler material in electric arc welding processes. Modular heat fields initiated by an electron‐beam‐welding‐process offers the potential of a time‐activated initiation of compressive stresses triggered by phase transformation of Low‐Transformation‐Temperature‐alloys. Developing a technology able to reduce residual stress and thus the deformation of complex welded components is the aim. The first approach of Low‐Transformation‐Temperature‐material used in the electron beam process and its behaviour is presented here.     

Influence on martensite‐start‐temperature and volume expansion of low‐transformation‐temperature materials used for residual stress relief in beam welding

Low‐transformation‐temperature materials (LTT) are used as high‐alloy welding filler material for high‐strength steels in order to minimize the tensile stresses and resulting distortion of the component during the welding process. The increase in the volume of the structure produced during martensitic transformation is utilized in order to counteract the volume shrinkage due to the cooling process. As stated in the field of study various elements influence the starting temperature of the martensite transformation, the influence on the volume expansion during the martensite formation is unknown. The influence of alloying elements nickel and chromium on the conversion behavior of low‐transformation‐temperature materials is to be investigated in detail. In particular, the effect of the variation of the mentioned elements on the starting temperature of the martensitic phase transformation and the extent of the volume expansion associated with that is investigated. In addition, the change in the hardness of the different low‐transformation‐temperature alloys is recorded and compared.     

直接光控晶闸管在脉冲电源上的应用

具有集成保护功能的直接光控晶闸管（LTT）是得到了广泛应用，这种晶闸管是为高压直流输电（HVDC）而开发的，通过改进门极结构，光控晶闸管也可用于大功率脉冲电源上，由于采用了直接光触发，LTT特别适用于串联应用。     

直接光触发晶闸管(LTT)在SVC的应用

与普通的电触发晶闸管ETT 对比, 直接光触发晶闸管LTT 具有直接光触发和内置BOD 保护两大优点, 使得LTT 阀塔的可靠性大大提高、维护量明显降低、成本显著节省。随着LTT 应用量的不断扩大和成本的进一步降低, LTT 技术在高压直流输配电换流阀和静态无功功率补偿装置( SVC) 等方面的应用前景广阔。