Nano-enabled metal oxide varistors

Zinc oxide based metal oxide varistors (MOV) are widely used electrical surge protection components. The design of modern high power, high-density electronic systems necessitate the need for smaller footprint, higher current density and higher nonlinearity MOVs. Such requirements can no longer be satisfied by commercially available MOVs due to their limited voltage capability, high leakage current and mechanical cracking related reliability issues, most of which are associated with the presence of defects and coarse granularity and lack of uniformity in their microstructures. New formulations and processes have been developed to overcome such limitations. This work has developed nano-enabled MOV compositions that can be sintered at relatively lower temperatures than typical commercial MOVs, but with largely improved I-V characteristics due to refined and uniform sub-micron structures. These nano-enabled MOVs show not only high breakdown strength (1.5 kV/mm) with low leakage current, but also a large nonlinear alpha coefficient > 50 at high fields, a measure of the speed of the transition from the insulating to conducting state and the effectiveness of over-voltage protection. A > 10x increase in breakdown strength compared to commercial MOVs, along with much higher nonlinearity, will enable MOV miniaturization, high voltage surge protection, and open up new areas of application.     

低β值给水流量喷嘴的异种钢焊接

在低β值给水流量喷嘴安装中,采用A307焊材对Q345R主管道和304不锈钢喷嘴进行焊接,焊后的检测结果表明,焊接工艺满足DL/T 752—2001规定;焊接接头无裂纹和超标缺陷,符合JB 4730—2005.3Ⅱ级要求;水压试验无泄漏,无可见的异常变形,无异常响声;喷嘴有轻微变形,但可满足测量精度要求。     

绕组交叉换位对高频变压器参数影响的分析

为了掌握不同交叉换位结构对变压器参数影响的情况,针对平面卧式变压器,利用有限元分析(FEA)方法计算变压器窗口内磁场能量,将绕组交流电阻和漏感随交叉换位的变化进行量化,获得了KR、KL两个系数来分别表征线圈交流电阻和漏感的变化规律。实例计算验证了系数的有效性,即已知一种绕组结构的交流电阻和漏感,就可利用这两个系数通过简单计算获得其它形式绕组结构的参数,此为高频变压器的初期设计提供有效支持。     

Comparison of the Electrical Characteristics of PZT and SBT Thin Films

The electrical properties of lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) thin films are compared for nonvolatile random access memory applications. PZT thin films have high switchable polarization with poor fatigue resistance and higher leakage current densities as compared to SBT thin films deposited on platinized silicon substrates. Characterization of these films in terms of their domain dynamics under application of sub-switchable and switchable electric fields give valuable insight about the observed differences in the electrical behavior. In the present work the dielectric behaviors of SBT and PZT thin films at sub-switchable electric field were analyzed in terms of Rayleigh law. The reversible and irreversible polarization component of switchable polarization was separated by the measurement of capacitance-voltage (C-V) and polarization hysteresis loops. The conduction mechanisms in these films were evaluated by measuring field dependence of leakage current densities at various temperatures. The observed differences in electrical properties are explained in terms of the intrinsic defects and defect-domain interaction of these two materials.     

不同体系低温无铅玻璃在铜端电极浆料中的应用

研究了4种不同体系低温无铅玻璃粉在多层陶瓷电容(MLCC)铜端电极浆料中的应用。通过DSC、SEM等测试玻璃的玻璃化转变温度、析晶温度、烧结特性、耐酸性,并研究了玻璃粉对MLCC力学性能、电性能的影响。4种低温无铅玻璃的玻璃化转变温度不同,适合的烧结温度也有不同。在合适的烧结温度下,4种低温无铅玻璃均可以提供良好耐酸性、致密的端电极表面及合格的端电极附着力和MLCC电性能。2#(B-Zn-Na-Cu)玻璃的综合性能最优,满足MLCC对端电极浆料无铅低温高可靠性的要求。     

基于多种检测手段的高压电缆头绝缘放电诊断分析

高压电缆头制作由于结构封闭、部件复杂以及电场均匀度要求高,一直是一个难题。在利用红外精确测温、超声波和高频电流局放检测法的基础上,创新性地引入了X射线吸收衬度成像技术对电力电缆头进行无损检测。通过多种检测手段综合诊断及解体论证,对一起35 kV单芯高压电力电缆头绝缘放电案例进行了详细分析。分析结果表明：X射线吸收衬度成像技术能够有效辅助查找高压电缆头在制作或使用中老化产生的孔洞、裂缝等缺陷;多种检测方式相互验证,可以提高缺陷定性分析的准确率。文中率先将X射线吸收衬度成像技术应用于工程现场,实现通过图形查找高压电缆头故障缺陷,提高电力电缆故障诊断直观性和可靠性。     

防爆电机铸件过滤网应用技术

生产实践表明采用铸型过滤网技术生产防爆电机铸件可大大降低铸件出现渣、砂、缩孔等缺陷。     

750kV串抗并联避雷器泄漏电流表指示异常分析研究

针对一起换流站串抗避雷器的电流泄漏电流表出现指针异常满偏问题进行故障诊断,理论分析可能引起泄漏电流表指示异常的原因,通过开展一系列对比试验并结合建模仿真,重点研究了外界磁场和异常高电压对电流泄漏电流表指针偏转的影响,结果表明泄漏电流表指针偏转与串抗周围强磁场环境无关,而与其下引线处异常高电压有关。经综合分析,确定该电流泄漏电流表同避雷器并接于线路串抗两侧,其下引线处因无法接地而存在异常高电压是引起指针异常满偏的主要原因,随后提出处理建议。     

Electrical performance of RTV silicone rubber coatings

The role played by two major constituents in a room temperature vulcanized (RTV) silicone rubber coating, namely, the inorganic alumina trihydrate (ATH) filler and the silicone polymer, on the coating's electrical performance was examined. The principal variable in the RTV silicone rubber coatings evaluated was the different weight fraction of the silicone polymer and ATH inorganic filler normally used for improving the tracking and erosion resistance. Other formulation details were essentially the same in the cured rubber. The coatings were spray coated on glazed porcelain rods and subjected to accelerated aging in a salt fog chamber. The changes produced by accelerated aging on the contamination withstand capability, leakage current suppression and erosion resistance were determined and correlated with the ratio of polymer to inorganic filler in the coating. It is shown that critical aspects of electrical performance necessary for satisfactory service operation such as contamination withstand capability before flashover and leakage current suppression are superior for the coating with a relatively high ratio of polymer to inorganic filler in comparison to the coatings with a relatively low ratio of polymer to inorganic filler. While all the coatings showed a high erosion resistance under mild discharge activity, the erosion resistance was found to be superior for the formulations with high inorganic filler under conditions of intensive surface discharge activity     

快速充电型Cd-Ni电池的研究

介绍了采用烧结式镍正极与拉浆式镉负极匹配制备快速充电型Cd Ni电池的研究。通过对镉负极的改进和选择低电阻高透气率隔膜 ,提高了镉负极吸氧能力 ,降低了电池内阻 ,大大改善了电池的大电流过充能力 ,使半烧结式SC型Cd Ni电池 ,即使采用 1C充电 1 .75h ,电池也不鼓底、不泄气 ,最高充电电压控制在 1 .6 0V以下 ,同时电池还具有良好的大电流放电能力和循环寿命性能 ,其 1 0C放电 3min时的放电电压大于 1 .0 7V ,采用 1C充电1 .5h ,1 0C放电至 0 .8V的循环寿命性能明显优于常规Cd Ni电池。批量生产结果表明 ,改进的快充型Cd Ni电池重复性及稳定性均好 ,适合于大规模生产。