Electrically induced heat dissipation in metallized film capacitors

Elevated temperature is a key aging factor for metallized polymer film capacitors with the capacitor life expectancy halved with every 8/spl deg/C of temperature rise. For film capacitors in service, both application of a time-varying external voltage and the extinction of internal breakdown events can deposit significant heat onto the capacitor structure leading to an undesirable temperature rise. Often such heat generation is localized spatially and the resulting temperature gradient enhances the probability of subsequent breakdowns. To facilitate a thorough and generic understanding, a thermal model of metallized film capacitors is developed to simulate the dynamics of heat generation and transfer under the switching impact of an external voltage. Thermal processes in solids (polymer layers, electrode coating, and zinc-spray segment) are modeled with conduction mechanism, whereas convection mechanism is considered for silicone oil and air. Heat generation is induced either by ohmic losses of the externally applied electric field, or by internal breakdown events within the metallized film capacitor structure. This allows a seamless interface between the heat transfer model and the equivalent circuit based field calculation model. Based this electrothermal model, numerical examples are used to study temperature distribution within film capacitors and then to examine the likelihood of localized temperature hot-spots that may lead to spatially preferential breakdowns.     

离子束溅射淀积光学薄膜的膜厚均匀性实验

介绍了离子束溅射技术改善薄膜均匀性的两种方法。研究了修正板技术,根据工程需要将修正板技术应用于行星转动条件下的光学薄膜的均匀性修正。分别研究了靶摆动和不摆动的情况下,淀积薄膜的均匀性修正。实验结果表明,修正后的均匀性结果优于 1%,能满足实际应用的要求;靶摆动修正的均匀性结果优于修正板技术。     

以人为本抓管理依靠科技求发展

天铁劳动服务实业有限公司坚持依靠科技进步和技术创新,不断改造现有设备,提高装备水平,研制新工艺,新 材料,使劳服公司为天铁集团的稳定和发展及进步奠定了基础。     

智能卡话者确认系统的研究

介绍了一个将参考模板存放在智能卡上的与相关的话者确认系统及其工作原理、相关算法和参数设置。     

苛性碱分解高钙黑钨精矿试验研究

研究了在高温，高压（Ｔ＝１８０℃，ｐ＝１．０～１．２×１０＾６Ｐａ）的加磷酸盐情况下，苛性碱分解高钙黑钨精矿的工艺，试验表明，高钙钨精矿的分解率（η）可达９８％以上，钨酸钠溶液中Ｐ／Ｗ比值也能满足工艺要求，与常温，常压工艺相比苛性碱的用量降低，分解时间缩短。     

镀锌产品表面粗糙度影响因素的研究

以马钢第四钢轧总厂1#镀锌线的产品为研究对象,通过大量的数据检测,分析了热浸镀锌产品带钢表面粗糙度的影响因素,并得出变化规律。这些规律可以运用到实际生产中来对带钢表面的粗糙度进行计算和控制。     

电子新品可靠性技术

文中分析了新研制电子产品的可靠性技术的有关问题，在明确这些问题实质的基础上提出了解决的措施和办法。     

退火炉自动控制系统设计

山东烟台钢管总厂冷拔分厂退火炉自动控制系统的设计以微机、智能仪表、变频调速器为主,具有控制精度高、降低消耗、操作维修方便、提高劳动生产率等特点。