基于ICE2PCS05高功率因数校正电路的设计

以单相Boost有源功率因数校正电路为研究对象,分析有源功率因数校正技术的基本原理及其分类,并对每一类型电路的拓扑结构、工作特点及工作方式进行比较。逆变焊机输入整流电路中的滤波电容是导致输入电流波形畸变的原因所在,产生高次谐波,并降低电源的功率因数。基于新型功率因数校正芯片ICE2PCS05,设计一款功率为300 W,输出为400 V的高功率因数校正电路,详细分析该电路的工作原理、升压电感、电容、功率开关管、二极管、开关频率和ICE2PCS05外围电路等部分参数的设计方式,并给出其测试结果。实验结果表明,该设计电路合理可行、输入电流畸变小,输出电压恒定,可获得高功率因数。     

电阻焊逆变电源的simulink建模及仿真

为了研究逆变电阻点焊系统工作特性及元件参数对系统响应的影响,采用MATLAB中的仿真工具对逆变电源、焊接变压器、整流器及其负载等各部分进行仿真分析,对不同滤波电容和次级负载情况下的输出波形进行了理论分析和仿真模拟.结果表明,滤波电容的选取,应使整流电路输出电流呈断续脉冲形态,由整流器和电容在电压高峰和低谷之间轮流向负载供电.次级电流沿指数曲线上升,且上升速度与次级回路电感成反比,但只要通电时间够长,次级电流最终达到的稳态幅值不受电感影响.     

晶闸管导通角的数控电路分析

某生产机械的动力装置为晶闸管控制的桥式整流电路 ,通过调整晶闸管导通角的大小来实现直流调压。由于生产工艺流程的变更 ,要求用数控装置的二进制代码来实现自动调压。图 1就是利用数控装置输出的二进制代码控制晶闸管Ｖ10的导通角 ,实现数控自动调压的。见图 1,二极管Ｖ1、Ｖ2、Ｖ3、Ｖ4组成桥式整流电路 ,通过二极管Ｖ5和电容Ｃ1滤波输出直流电压ＵＤＤ为电路提供直流电源。在桥式整流电路的输出电压中 (见图 2 ) ,只有过零点附近很短的时间内为低电平 ,使三极管Ｖ6截止 ,集电极输出高电平 ,而在大部分时间内Ｖ6处于饱和状态 ,输出低电…     

高铁中倍压整流电路的原理分析与仿真

传统高电压输出电源采用变压器升压时,变压器二次绕组的匝数增加,导致运行时产生充放电电流和噪声,同时使变压器的一次侧、二次侧产生能量损耗。为解决该问题,采用电力电子技术和倍压整流方法,分析两种常见的倍压整流电路——半波倍压整流和信克尔倍压整流,通过仿真分析,对比两种倍压整流电路的特点,信克尔倍压整流电路的输出脉动电压远小于半波倍压整流电路,输出电压建立时间短于半波倍压整流电路,输出电压高于半波倍压整流电路。     

等离子弧切割机中IGBT半桥逆变电容的研究

IGBT半桥逆变电路中的电容既是整流电容,又是逆变半桥电容,其值的大小对逆变半桥电路工作有很大的影响。为了限制该电容的充电电流,设置限流电感,但限流电感会造成IGBT过压。采用Amtlab软件研究限流电感对电容充电过程的影响,获得3 700μF时合理的限流电感值。研究半桥逆变电容值的大小对输出电流、电压的影响,在一定的输出电流的条件下,输出电压越高,所需的电容值要求越大,才能保证切割过程稳定。     

TIG焊倍压整流式引弧电路的设计与调试

如何既能保证引弧成功率高，又能实现以降低频率的方式减小对电网和控制系统的干扰，是设计引孤电路所要解决的问题。介绍了一种结构简单、燃弧率高、频率相对较低的引弧电路。以电容、二极管构成的倍压整流技术提升电压。并利用LC振荡在变压器二次侧耦合出高电压引弧信号。分析输出脉冲信号的驱动电路。并建立驱动电路模型，结合仿真研究。介绍其工作原理。     

晶闸管弧焊整流数字控制的研究

针对大功率弧焊整流焊机的工作环境及工作特点,本文详细分析了弧焊整流电源的拓扑电路以及数字控制的分析。在焊接过程中,根据焊接的需要其焊接电流值大小应实时变化,当通过改变SCR的触发角不能满足焊接功率时,可通过改变三相变压器输出的电压值来自适应焊接电流的大小,因此,本文采用了多输出变压器来满足宽范围的焊接电流值；在数字控制中采用DSP和FPGA共同实现焊接的电压、电流和温度采样以及用FPGA对SCR可靠稳定的触发。数字控制实现时是对焊接输出出的电压和电流进行采样,通过闭环进行PI控制运算,实现方法是采用DSP芯片处理器控制整个电焊机的性能和功能以及开关量信号的采样,由FPGA运算SCR触发导通角的大小,并发出触发信号让SCR可靠稳定的导通和关断。通过理论分析,实验验证了该控制系统拓扑电路的正确性以及控制方法的可行性,从而保证系统能稳定和可靠的运行。     

半桥逆变等离子切割电源主电路设计与仿真

等离子切割机输入电路采用半桥逆变电路,输出电路采用全桥整流电路,输出功率11 k W。分析主电路的工作过程,计算了IGBT和整流二极管等元器件的参数。输入电抗器和变压器一次侧的RC吸收回路作用的Matlab仿真结果表明:加入输入电抗器减少了合闸时换流电容充电电流的峰值;并联于变压器一次侧的RC吸收回路明显降低了IGBT关断时刻产生的电压尖峰。     

三相桥式整流功率因数校正的分析

针对三相桥式整流输入电源功率因数值较低进行分析,对三相桥式整流电路的不同拓扑电路结构及控制方法做出了分析和比较。通过引入Boost二级电路并采用滞环控制的方法,在三相输入端添设相应的滤波电路完成了对三相桥式整流输入电源功率因数的校正,有效的将三相桥式整流输入电源功率因数值从不加Boost二级控制时的0.950提升到0.994。所使用的电路具有结构简单,易于控制,成本低且性能高等优点,并通过Matlab/simulink的仿真验证及其相关数据的计算,证实了本研究所使用方法的优越性。     

单相电压型PWM整流器研究

现代轨道交通电气化中需要高效、高功率、稳定和可靠的整流电源,而整流电源会产生大量谐波导致网侧低功率因数运行和网侧电流波形畸变。分析单相电压型PWM整流器的拓扑电路结构及数学模型,采用一种基于幅相控制(phase and amplitude control-PAC)策略的间接控制方法,该方法是对桥侧交流电压基波分量的幅值和相位进行控制,从而实现对网侧电流的间接控制。仿真验证了该控制策略网侧功率因数达到0.99以上,网侧电流THD低于5%,同时满足能量双向流动和输出电压可调的要求。     

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。     

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.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

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.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.     

Laser Cladded TiCN Coatings on the Surface of Titanium

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

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.     

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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