集成磁技术和恒频脉宽调制的谐振开关变流器分析及优化设计方法

集中分析及研究了谐振开关变流器的工作原理和控制方法,并建立了改进型谐振开关变流器各个工作模式的转换条件;针对各种谐振型开关变流器进行优化分析和设计,对谐振型开关变流器电路拓扑结构提出了相关优化电路结构;在此基础上,进一步减小变流器磁性器件的体积、重量和损耗,研究了集成磁技术,即把开关变流器中所有主要磁性器件从结构上集中在一起,用一个磁性器件来实现,经过优化设计,磁芯当中的磁通变化量减小,从而降低磁芯损耗,减小磁芯体积.通过电路分析、计算机仿真以及变流器电路实验,证实了优化后变流器所具有的优点.     

两相电磁搅拌逆变器主电路与参数设计

提出了一种适合两相电磁搅拌逆变器的主电路选择方案，计算功率器件IGBT的导通损耗、瞬时开关损耗值和器件温升的方法。提出了在电磁搅拌逆变器中采用两相半桥和两相全桥拓扑结构的功率、电压、电流限制范围与设计准则。合理选择电磁搅拌逆变器的拓扑结构和参数，能够提高功率器件的利用率和可靠性，降低控制电路的复杂性和主电路的成本。     

SQUID读出电路的仿真及其调试电路的设计

超导量子干涉器件(SQUID)配合其读出电路可实现极其微弱磁场的测量,设计低噪声高性能的读出电路是SQUID应用中的一个重要工作。本文介绍了根据电路数学模型进行电路行为仿真的方法,对电路进行模块划分,建立各模块的数学模型,通过仿真分析影响电路性能的关键参数,进而指导具体电路的设计实现,同时介绍了一种调试电路的研制,可实现基于交流调制的磁通锁定式读出电路在常温下的调试。     

全桥式逆变电路抗单向偏磁自动调节保护电路

本文提出了全桥式逆变电路抗单向偏磁自动调节保护电路。该电路通过提取变压器承受的双向电压信号和工作磁通信号以及实时进行闭环反馈控制,保证了全桥式逆变焊接电源的变压器正反向工作磁通相等,从而解决了全桥电路的不平衡问题。     

FeCoV/Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3/Ni薄膜复合结构的磁电效应

为了适应器件的小型化、提高薄膜两相复合磁电材料的磁电效应,采用磁控溅射方法在Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT)衬底上生长FeCoV薄膜和Ni薄膜,形成FeCoV/PMN-PT/Ni薄膜复合结构。采用动态磁电系数测量系统对复合结构的磁电性能和共振频率进行了研究。结果表明:复合结构的磁电系数随直流偏置场的增加呈现先增加后减小的趋势,在约39.8kA/m附近达到峰值17.8×10-3 mV·cm-1·A·m-1,在31.84kA/m的直流偏置场下,磁电电压随着交流激励场强度的增加呈线性增加。复合结构在85.5kHz下具有一个明显的共振峰,在共振频率下,磁电性能提高5倍以上。     

逻辑电平的转换电路

在改造机床的数控装置时，由于机床上传感器电路输出的高电平为24伏，低电平为3．2伏，和数控装置的TTL电平不能匹配，为此，我们增设了逻辑电平转换的接口电路，将机床上高电压逻辑电平转换为低电压逻辑电平，使其适应TTL电路的要求。同时，将TTL发出的串行数据转换成高电平为5伏、低电平为5伏的传输信号送入计算机的接口中，以提高信号的噪声容限和传输中的抗干扰能力c其电路如图1所示。集成运放采用电压比较器LM339，一块LA339中一共有4个电压比较器，图中只用～个。S；一马为CMOS双向模拟开关CD4the，当控制端为高电平时开关接…     

焊接系统中直流电机速度调节的实现

研究了焊接系统中直流电机的速度调节,提出了一种新型的拓扑电路结构,通过控制上下桥背的高频开关导通后,再经过变压器进行电压变换,使直流电机得到稳定可靠的直流电压.为了让开关管能实时得到触发信号,也对采样电路进行了设计,该采样电路能对电压和电流信号实时精确处理,理论分析了变压器设计的参数,通过设计指标理论计算出变压器和各器件的参数值.最后进行了样机实验,验证了本研究提出电路拓扑结构和电路参数的可行性.     

基于DSP的点焊逆变电源硬件控制系统研究

分析了以数字信号处理器(DSP)为核心的逆变点焊电源的控制电路,按照系统要求对DSP进行了I/O扩展,根据实际进行了电平转换.并设计了电压电流采样、键盘及显示等外围电路,实现双闭环控制;为保护焊机的功率器件设计了过压欠压电路.硬件电路测试表明所设计的硬件系统满足要求.     

基于SMES的动态电压恢复器的补偿策略研究

介绍了基于超导磁储能的动态电压恢复器的电路结构和补偿控制原理,提出了一种基于最佳实用性的电压补偿控制策略,该补偿控制策略能使动态电压恢复器在工作时输出较小的能量并保持高质量的补偿效果,并在MATLAB中模拟配电系统中负载端发生电压暂降时动态电压恢复器的工作情况,从仿真计算结果中能看出新型补偿策略能为装置带来更好的综合性能。     

零电压、零电流倍流整流电阴焊逆变电源

设计了一种新型的零电压、零电流倍流整流电阻焊逆变电源,采用移相控制实现零电压、零电流开关全桥变换,其中超前桥臂实现零电压开通,滞后桥臂实现零电流关断。变压器二次侧采用一种单线圈双电感双管全波整流电路,整流二极管实现零电流自然关断,逆变器所有的功率器件都工作在软开关状态,降低了功率器件的应力和开关损耗,提高了弧焊逆变器的电磁兼容性能力,突出了逆变电源节能、体积小、质量轻、响应速度快的优点,特别适合大功率场合。     

Advantages of asymmetrical over symmetrical cells for detection of under deposit CO2 corrosion using electrochemical noise

Electrochemical noise (EN) measurements were done on symmetrical and asymmetrical cells after immersion in 3.5% NaCl solutions saturated with CO₂ and containing different concentrations of sodium bicarbonate to get a better interpretation of the under‐deposit corrosion of mild steel. The symmetrical cell was constructed from two sand‐deposited electrodes and the asymmetrical cell was prepared from one sand‐deposited electrode and one bare electrode. The combination of the standard deviation of partial signal (SDPS) plots arising from wavelet analysis and recurrence plots for analyzing the EN signals obtained from symmetrical and asymmetrical cells confirmed the higher detective ability of the asymmetrical cells in comparison with the symmetrical cells for measuring the under‐deposit corrosion of mild steel. Both the SDPS and recurrence plots arising from symmetrical cells showed no significant change in the corrosion severity of the steel alloy with adding sodium bicarbonate. In contrast, the SDPS and recurrence plots of the asymmetrical cells proved that the corrosion severity decreased initially with adding the bicarbonate and thereafter remained constant with increasing the bicarbonate concentration. The optical microscopy images of the sand‐covered electrode surface confirmed the latter result.     

Lithium-ion cell inconsistency analysis based on three-parameter Weibull probability model

The inconsistency of lithium-ion cells degrades battery performance,lifetime and even safety.The complexity of the cell reaction mechanism causes an irregular asymmetrical distribution of various cell parameters,such as capacity and internal resistance,among others.In this study,the Newman electrochemical model was used to simulate the 1 C discharge curves of 100 LiMn_2 O_4 pouch cells with parameter variations typically produced in manufacturing processes,and the three-parameter Weibull probability model was used to analyze the dispersion and symmetry of the resulting discharge voltage distributions.The results showed that the dispersion of the voltage distribution was related to the rate of decrease in the discharge voltage,and the symmetry was related to the change in the rate of voltage decrease.The effect of the cells' capacity dominated the voltage distribution thermodynamically during discharge,and the phase transformation process significantly skewed the voltage distribution.The effects of the ohmic drop and polarization voltage on the voltage distribution were primarily kinetic.The presence of current returned the right-skewed voltage distribution caused by phase transformation to a more symmetrical distribution.Thus,the Weibull parameters elucidated the electrochemical behavior during the discharge process,and this method can guide the prediction and control of cell inconsistency,as well as detection and control strategies for cell management systems.     

力学性能非对称焊接接头断裂特征参量研究

根据力学性能和几何的对称性,本文对焊接接头非均匀体进行了分类。研究了更接近实际情况的力学性能非对称的焊接接头非均匀体的断裂特征参量,以及力学性能非对称性对裂纹开裂角的影响。     

新一代几何模型（周模型）与对称和非对称模型的应用比较

编制了新一代几何模型（周模型）和其它几种对称和非对称几何模型的计算机应用程序,并计算了液态合金体系Ａｇ－Ｓｎ－Ｚｎ的混合自由能,结果表明,新一代几何模型的应用更为合理,可靠,而且克服了人为的因素,并用利于计算机程序化。     

变截面零件辊锻过程数值模拟优化

采用美国MARC公司的MSC／superform软件对叶片辊轧工艺进行了数值模拟。模拟建立两种有限元模型——对称模型和非对称模型，在两种模型下分别分析了坯料与轧辊之间的摩擦系数对中性角的影响，得出中性角随摩擦系数增大而增大，前滑区变形金属随之增多。反之，摩擦系数过小影响坯料的正常咬入，出现打滑现象。模拟结果显示摩擦系数取0．3为最佳选择。在不同模拟模型下不同型槽内变形区金属的流动情况不同。非对称型槽成形的工件由于上下表面金属流动速度不同，出现弯曲现象；对称型槽成形的工件较平直。因此，为保证叶片的成形质量，设计选用对称型槽形式。通过数值模拟优化设计工艺参数，为叶片辊轧工艺的制定提供依据。     

Detection of plastic deformation in low carbon steel by SQUID magnetometer using statistical techniques

In order to non-destructively detect the amount of plastic deformation accumulated in low carbon steel of S25C, the distribution of localized magnetism has been measured for plate-type S25 tensile specimens with plastic strains up to 6.45% by ultrahigh sensitive magnetic probes using superconducting quantum interference device (SQUID). The slope value obtained from the SQUID signal pattern, which means the ratio of the change in SQUID output voltage to the change in AC current flow in the superconducting magnet, was chosen as a candidate indicator to detect plastic strains in the present study. For quantitative assessment, statistical processing was performed for determining the datum of the distribution of the slope value. As a result of the statistical approach, small-scale plastic deformation could be detected on S25C tensile specimens. It was suggested that the magnetic measurement using SQUID magnetometer supported by the statistical techniques was a promising non-destructive evaluation method to detect the amount of plastic deformation accumulated in low carbon steel.     

电液比例对称阀控非对称液压缸的模型研究

针对阀控液压缸的建模,分析现有研究成果的特点。现有建模过程中需要线性化近似,同时负载压力、负载流量的定义多样化,虽然最终可以建立统一的传递函数,但传递函数的系数不确定性因素较大,这将直接影响高精度的应用。从工程角度出发,重新定义负载压力、负载流量的概念,推导出对称阀控非对称液压缸两个方向的传递函数,并对其进行进一步的分析,为电液比例对称阀控非对称液压缸系统的高精度应用提供了参考。     

Evaluation of the localized corrosion on Mg electrode surface by electrochemical noise technique

The symmetrical and asymmetrical electrodes made of Mg were studied in 0.1-M NaCl electrolyte adjusted at pH 12. The statistical and wavelet methods were employed for analyzing the electrochemical current noise (ECN) signals. The asymmetric configuration was used for electrochemical detection of filiform corrosion on Mg electrode. The real time scale of the dominant transients of the asymmetric electrodes was detected on the basis of the maximum peak in the SDPS plots. The SDPS values of the real time scale crystals of the ECN signals resulting from asymmetrical electrodes increased with the increase in immersion time due to the onset of filiform corrosion.     

刀具钝化非对称刃口对铣削温度场影响的研究

刀具刃口通过钝化可以去除刃口缺陷,提高刀具使用寿命和切削过程的稳定性。刀具钝化刃口可以是对称的,也可以是非对称的。通过建模软件SolidWorks建立不同形状因子的非对称刃口二维模型,采用切削仿真软件ThirdWave建立硬质合金刀具钝化非对称刃口对铣削45钢过程的有限元模型,分析形状因子对温度场的分布规律,揭示刀具钝化非对称刃口对切削温度的影响规律,研究结果对于实现刀具钝化刃口优化,提高加工水平具有重要意义。     

Evolution of {001 } （110） orientation and related lattice rotation of A1 alloy 6111 during rolling

The texture evolution and lattice rotation in A1 alloy 6111 with an initial {001} （110）component during symmetrical and asymmetrical roiling were investigated by means of orientation distribution function（ODF）. The results show that the as-rolled initial {001 } （110） orientation evolves into not only the copper orientation but also all the other orientations along the β fiber, including the brass orientation, by lattice rotation around special directions. Compared with the symmetrical rolling, the {001 } （110）component in the surface layer on the slower roller side evolves more quickly into the orientations along the β fiber during asymmetrical rolling, while that in the surface layer on the faster roller side evolves more slowly.