IGBT超音频感应加热电源用于发电机绕组焊接的研究

在大功率发电机生产行业，发电机绕组焊接工艺主要采用阻焊，其缺点是热效率低，焊接时间长，并且加热的温度不均匀，影响焊接质量。感应加热焊接法具有精确的加热深度和加热表面积，不需要外部热源，因而热量损耗低，工作环境清洁，且容易实现功率密集，因而加热时间短，容易实现生产过程的自动化。本文介绍的超音频感应逆变电焊机采用直流斩波调压方式，输出功率可从零开始调节。逆变器输出频率采用频率跟踪控制，IGBT工作在软件开关状态，减小了IGBT的开关损耗，提高了整体的功率因数，加热效率大大提高。     

智能型多功能弧焊逆变电源及其编程控制

基于短路过渡CO2 焊接短路阶段电源输出电阻的变化规律 ,确定了有利于消除瞬时短路及提高熔滴过渡规则性的控制电流波形 ;在此基础上 ,利用逆变弧焊电源的高速可控性 ,以MC6 8HC11A1单片机为主控建立的焊丝干伸长变化前馈———过渡频率负反馈控制系统 ,实现了波控恒频短路过渡CO2 焊接 ,极大地提高了焊接过程的稳定性和适应能力。通过对引弧瞬间电源输出短路电压的实时检测 ,实现了MMA焊电弧推力拐点电压随焊接电流及焊接电缆长度、截面积等改变的自动调节。采用键盘输入和液晶显示等直观输入输出设备 ,设计并实现了焊接方法与参数的编程控制。结果表明 ,系统工作稳定可靠 ,抗干扰能力强 ,具有推广应用价值。     

交流脉冲MIG弧焊电源及弧长控制

AC PMIG的控制模式是一周一脉一滴，脉冲电流设计在电弧EP极性时间里，其余时间均为基值电流。弧焊电源一次逆变控制电流快速动态过程，二次逆变控制电弧极性。控制系统采用双闭环结构，内环模拟控制电弧电流，外环80C196KC单片机控制电弧电压及电弧极性。根据电弧电压偏差信号及电弧状态，设计了四个控制规则及其控制参数的计算方法。正常焊接状态时变频控制交流脉冲频率。采用这种控制方案，获得了稳定性高、熔滴过渡均匀的焊接过程。     

一种新型串联逆变、模块化感应电源技术

感应加热技术是利用电磁感应原理,通过交变电流在工件中产生涡流来加热工件的.由于感应加热具有加热速度快、发热在物料内部和热效率高、温度控制精度高、加热均匀、产品质量好、加热氧化皮少、模具费用和营运成本低、无环境污染以及可控性好且易于实现自动化等一系列优点,近年来在中国的应用越来越多.感应加热设备的心脏部分--感应电源工作原理及组成部分如图1、2所示.     

造船厂CO2焊机局域网监控系统研究

造船厂CO2焊机使用数量大、安装位置分布广,焊接材料、电能消耗、焊接工作量及焊接生产效率实时统计困难;焊接参数及焊接质量可控性较差.目前造船厂大量使用的CO2焊机都是通过6根控制电缆在焊接电源与送丝机之间进行参数调节,因而控制电缆容易损坏且不能进行信息统计分析和参数控制.论文以对焊接材料、电能消耗、焊接工作量及焊接生产...     

大电流接触器触头高频感应钎焊工艺

O 前言 随着我国工业的快速发展,对低压电器提出了高品质、高可靠性、小型化的要求,使用范围和性能要求亦更加宽阔和优良.大电流接触器触头焊接是低压电器产品制造中关键工序之一,提高触头焊接质量,是提高接触器使用寿命的重要环节.目前,国内外对接触器触头的焊接主要采用钎焊方法,钎焊又分为电阻钎焊(电极为合金或石墨材料)、炉中钎焊、火焰钎焊和高频感应钎焊.与电阻钎焊、炉中钎焊、火焰     

精密点焊电源任意波形控制系统

对所研制的由８０９８单片机控制的ＭＯＳＦＥＴ精密点焊电源的硬件及软件进行了介绍。该电源适用于桥带等金属箔,线件的精密点焊,通过对是电流瞬时值的精确控制。可输出任意特殊及复杂形状的波形,从而使不同尺寸,材料的工件都可实现最佳电流波形点焊。该系统还采用一台工业ＰＣ机对焊接过程及各种参数进行监控和管理,进一步提高了焊接质量及自动化水平。     

MCU与DSC对感应加热电源的网络化远程监控与实现

针对传统的高频感应加热电源操作安全性差、自动化程度低、难以实现网络化控制等缺点,设计了一种基于微控制器(MCU)和数字信号控制器(DSC)的新型高频感应加热电源网络化远程监控系统.该系统采用RS-485总线和Modbus通信协议,便于组网和改善通用性.介绍了该控制系统的组成和工作原理,给出了软硬件设计.试验证明控制系统实现了高频感应加热电源的网络化远程监控,提高了系统的自动化水平.     

中频钎焊在高压开关触头焊接中的应用

触头元件由紫铜（铬铜）与（CuW70）组成,在开关设备中起着关键作用,承受高温、高压、耐磨,并有一定的强度要求。其焊接质量的好坏直接关系到开关产品质量的优劣。我厂对触头焊接过去都是采用火焰钎焊,效率低、成本高、合格率低,严重地制约着生产。为了解决这个难题,通过大量工艺试验和详细论证认为,高速局部加热,氧化少、硬度降低小、效率高的中频感应加热是触头焊接的最有效的方法。     

软斩波功率控制IGBT四倍频300 kHz/50 kW焊接电源

提出了一种IGBT四倍频分时控制300kHz大功率感应焊接电源．功率调节由三相桥式不控整流电路和直流斩波电路组成,斩波电路采用有源无损缓冲Buck变换器,在较宽的负载范围内使主、副开关管和续流二极管均实现软开关．采州四组IGBT并联的逆变器,对每个IGBT进行分时控制,逆变器的工作频率是IGBT开关频率的四倍．逆变器工作在负载谐振状态,开关管工作在零电流开通和零电压关断的条件下．设计了输出300kHz／50kW的串联谐振感应焊接电源,给出了设计参数和试验波形．结果表明．采用四倍频分时控制的方法,用IGBT替代功率MOSFET制作高频大容量感应加热焊接电源成为可能．     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.