多芯片并联压接式IGBT中温度不均对电流分布的影响

多芯片并联的压接式IGBT器件是柔性直流输电设备中的关键部件,因制造工艺、回路寄生参数和热耦合问题使得器件内部应力分布不均,造成器件不均匀老化,使得内部温度不均程度加剧,进而使得电流分配不均。围绕不同温度差异下导致的电流分布不均问题展开研究。首先,对造成IGBT器件并联不均流的原因以及温度对不均流特性的作用进行分析。然后,利用单芯片压接式IGBT器件并联模拟多芯片器件内部的温度分布不均情况,进行温度分布不均匀程度对电流分配影响的实验。最后,通过实验验证并联器件间温度差异与不均流程度的关系。所提方法为提高器件的运行可靠性和对压接式IGBT失效机理认知奠定基础。     

Interdiffusion behavior of Al‐rich oxidation resistant coatings on ferritic–martensitic alloys

Interdiffusion of thin Al‐rich coatings synthesized by chemical vapor deposition (CVD) and pack cementation on 9Cr ferritic–martensitic alloys was investigated in the temperature range of 650–700 °C. The compositional changes after long‐term exposures in laboratory air and air + 10 vol% H₂O were examined experimentally. Interdiffusion was modeled by a modified coating oxidation and substrate interdiffusion model (COSIM) program. The modification enabled the program to directly input the concentration profiles of the as‐deposited coating determined by electron probe microanalysis (EPMA). Reasonable agreement was achieved between the simulated and experimental Al profiles after exposures. The model was also applied to predict coating lifetime at 650–700 °C based on a minimum Al content (C_b) required at the coating surface to re‐form protective oxide scale. In addition to a C_b value established from the failure of a thin CVD coating at 700 °C, values reported for slurry aluminide coatings were also included in lifetime predictions.     

包埋渗铝法制备Fe-Al渗层及其扩散机制

包埋渗铝法可在钢基体表面制备出一层致密、坚固、连续的Fe-Al渗层，以改善基体性能。本文在不同温度和不同时间下对Q235低碳钢进行包埋渗铝，形成Fe-Al渗层，采用X射线衍射、扫描电镜及能谱分析等方法研究了渗铝层的物相结构、表面及截面形貌和成分，采用显微硬度仪测量了截面硬度。结果表明，不同渗铝温度下获得的渗铝层，主要含有Fe₂Al₅和FeAl₃两相，且750℃得到的渗层存在较多Fe₂Al₅相；随着渗铝温度升高，Fe-Al渗层厚度增加，Al原子扩散系数增大，但显微硬度降低；不同渗铝时间下制备的渗铝层，物相仍以Fe₂Al₅和FeAl₃为主，但随着渗铝时间延长，FeAl₃含量减少，且Al原子扩散系数变大，渗层显微硬度略有降低。在进一步分析Fe-Al渗层形成的热力学与动力学基础上，总结了渗铝层形成的扩散机制。     

Establishing multilayered coating on Mo–12Si–8.5 B alloy by Si pack cementation and its oxidation behavior at 900°C–1300°C

A multilayered oxidation protection coating consisting of MoSi₂ outer layer, Mo₅Si₃ internal layer, and Mo₅SiB₂/MoB inner layer was developed on the surface of Mo–12Si–8.5B 1.0 wt% ZrB₂ alloy via Si pack cementation. The multilayered coating significantly enhanced the oxidation resistance of the alloy at 900°C, 1100°C, and 1300°C in the air by exhibiting negligible oxidation recession. MoSi₂ outer layer provided admirable oxidation protection for the alloy at high temperatures by forming a thin and protective SiO₂-rich glass scale on its surface. This was supplemented by the Mo₅Si₃ internal layer and Mo₅SiB₂/MoB inner layer that reduced the thermal expansion mismatch between the MoSi₂ outer layer and substrate, and therefore no obvious cracks were found in the MoSi₂ outer layer. More importantly, the Mo₅SiB₂/MoB layer as an in situ barriers of Si interdiffusion ensured the stable existence of MoSi₂ and Mo₅Si₃ layers without obvious thickness change during oxidation at 900°C and 1100°C. Mechanical property test indicated that the formation of the coating layers could not affect the fracture toughness of the alloy.     

Oxidation of a novel CeO2‐dispersed chromium coating in wet air

An electrodeposited Ni–CeO₂ composite was used as a “precursor film” for a novel CeO₂‐dispersed chromium coating deposited using a traditional pack cementation method. The substrate was a carbon steel. For comparison, chromium coatings were also prepared on the untreated and pure Ni‐film‐treated carbon steel using the same pack cementation conditions. Oxidation in 5% O₂ + 40% H₂O + N₂ at 900 °C showed that, compared to the CeO₂‐free coating counterparts, the CeO₂‐dispersed chromium coating exhibited greatly increased oxidation resistance, owing to the development of a denser and more slowly growing chromia scale. The slow growth of the scale was correlated with the CeO₂ dispersion exerting the so‐called “reactive elemental effect (REE)” on oxidation. The oxidation mechanisms in wet air of the various types of coatings were compared to those in dry air and are fully discussed in this work.     

通信基站用电池组负荷要求与设计应用

通信基站用电池组系统质量比较大，将其安装在楼层上时，设计及布局对建筑物本身的安全有着较大影响。本文对通信用户提出的负荷要求进行了分析计算，为电池组的设计和布局提供了理论依据。     

Gas‐producing and spoilage potential of Enterobacteriaceae and lactic acid bacteria isolated from chilled vacuum‐packaged beef

This study aimed to enumerate and identify lactic acid bacteria and Enterobacteriaceae from spoiled and nonspoiled chilled vacuum‐packaged beef and determine their potential to cause blown pack spoilage. These microbial groups were also enumerated in nonspoiled samples and detected in abattoir samples. The potential of isolates to cause ‘blown pack’ spoilage of vacuum‐packaged beef stored at chilled temperature (4 °C) and abuse temperature (15 °C) was investigated. Populations of lactic acid bacteria in exudate of spoiled and nonspoiled samples were not significantly different (P > 0.05), whereas the number of lactic acid bacteria on the surface was significantly higher (P < 0.05) in spoiled samples as compared to nonspoiled samples. The population of Enterobacteriaceae species in exudate and on the surface of samples were significantly higher (P < 0.05) in spoiled packs in comparison with nonspoiled packs. Results of the deterioration potential showed that ‘blown pack’ spoilage was noticeable after 7 days at 15 °C and after 6 weeks at 4 °C for samples inoculated with Hafnia alvei.     

基于参数分析的蓄电池模型健康状态估计

为了及时、准确地评价蓄电池的老化水平,保证其应急放电时刻的输出性能,基于备用蓄电池组定期维护放电阶段的背景,对蓄电池健康状态(SOH)的估计方法进行研究.首先,利用仿真试验,验证了可较好反映其内部特性的二阶RC电路模型作为蓄电池模型的合理性以及模型参数辨识的准确性.然后,通过对同一型号铅酸蓄电池进行老化试验,分析蓄电池...     

基于钛酸锂电池的离线均衡研究

以东芝钛酸锂电池组为研究对象,设计电池组的均衡方案,选择了能耗型均衡方式来实现电池组均衡,并且对不同情况下的电池组进行均衡实验。最终验证设计方案可靠,能对电池组进行有效均衡,从而提高了电池组的利用效率。