Screen-printed piezoceramic thick films for miniaturised devices

The development towards smaller devices with more functions integrated calls for new and improved manufacturing processes. The screen-printing process is quite well suited for miniaturised and integrated devices, since thick films can be produced in this manner without the need for further machining. On the other hand, the process of screen printing thick films involves potential problems of thermal matching and chemical compatibility at the processing temperatures between the functional film, the substrate and the electrodes. As an example of such a miniaturised device, a MEMS accelerometer based on PZT thick film will be presented. The design and process flow of this accelerometer has been optimised by means of finite element modelling (FEMLAB©). Consequently it has proved possible to eliminate post-processing steps after the screen printing of the PZT thick film.     

Heat generation in 1–3 piezoceramic—polymer composites

This paper describes the mechanism of heat generation in lossy 1–3 piezoceramic- polymer composite active layer of ultrasonic transducers excited at different voltages at resonance and off-resonance frequencies. The physical parameters controlling the heat generation and dissipation are estimated by least squares fitting the experimentally measured time-temperature profiles to a theoretical model. The theoretical profiles agree well with the measured data. The temperature rise at resonance frequency (250 kHz) and at an off-resonance frequency (30 kHz) is found to be 54 °C at 13.2 V_p-p and 38 °C at 169 V_p-p, respectively. The temperature rise, the total loss and the radiation heat transfer coefficient are found to vary quadratically with driving electric field. The convection heat transfer coefficient is estimated to be in the range (6–10) Wm^?2?K^?1, validating the free convection in air. Variations in the physical parameters with applied voltage are found to be different at resonance and off-resonance frequencies, indicating that the process of heat generation in piezocomposite transducers depends on the frequency region in which they are operated, with respect to the resonance frequencies.     

Nonlinear elastic phenomena near the radial antiresonance frequency in piezoceramic discs

The aim of this work is to study the nonlinear behaviour of a ceramic through the analysis of the radial mode at resonance and antiresonance frequencies. To obtain the nonlinear characterization from the impedance measurements, a correction of the current and impedance is proposed in order to obtain simple relationships between the motional impedance and the mean stress. The obtained relations are weakly dependent on frequency. This behaviour is also verified at resonance and at antiresonance. We use a nonlinear model where the elastic, dielectric and piezoelectric coefficients depend on the mean amplitude of the stress, which is more complete than the discrete elements models (RLC type), that are fulfilled only near the resonance.     

Numerical modelling of ceramic mems structures with piezoceramic thick films

The correctness of the material parameters that are used in numerical models is of key importance for any numerical analysis. Because of a lack of available material parameters and standard procedures for characterising piezoceramic thick films, special attention has to be paid to providing data for accurate material models. In the presented work, thick-film (TF) lead–zirconate–titanate (PZT) structures made on different ceramic substrates were considered. In order to obtain proper material parameters for TF PZT some unconventional characterisation approaches were used e.g. nano-indentation test for evaluation of the compliance of the piezo film. The results of characterising TF PZT structures on two different ceramic substrates, Al₂O₃ and pre-fired low temperature cofired ceramic (LTCC), are presented. For validation purposes simple cantilever-type actuators were modelled using the piezoelectric coupled-field capabilities of the finite-element (FE) package Ansys/Multiphysics and simulation results were compared with the measurements of the real structures.     

变压器空载损耗中的磁滞损耗和涡流损耗的区分

介绍了区分变压器空载损耗中的磁滞损耗和涡流损耗的方法,阐述了测试原理.     

线损二项式在线损分析预测中的应用

通过引入线损二项式,以及对过境电量、供电量增长等单一影响因素的计算分析,提出了线损预测的一种思路。     

Lifetime of piezoceramic multilayer actuators: Interplay of material properties and actuator design

We report an investigation into factors limiting the functional lifetime of multilayer piezoceramic actuators. The study consists of a combination of lifetime experiments by means of an accelerated lifetime test, inspection of the actuator microstructure at different stages of the accelerated lifetime test, and numerical simulation of the displacements and mechanical stresses that arise during actuator performance. During the lifetime test, both displacement and electrical properties were measured. The results show a clear correlation between the microstructure and the mechanical stresses in the actuator, giving evidence that crack initiation starts early in actuator lifetime and humidity effects accelerate degradation. The numerical simulations performed provide clues for optimization of the actuator design with respect to stress development and performance. Attention is paid to the choice of adhesive interlayer and its effect on the performance and lifetime of the actuator.     

Cymbal actuator fabricated using (Na0.46K0.46Li0.08)NbO3 lead-free piezoceramic

(Na_0.46K_0.46Li_0.08)NbO₃ (NKLN8) lead-free piezoceramic was prepared by a mixed oxide route. The ceramic showed a single phase of orthorhombic perovskite structure at room temperature and a high Curie temperature of ∼430^∘C. A cymbal actuator using NKLN8 as the actuation element and titanium alloy as the endcaps was fabricated and characterized. A similar actuator with traditional Pb(Zr,Ti)O₃ (PZT) piezoceramic was also constructed for comparison. The results showed that the NKLN8 actuator has a higher fundamental resonance frequency of 107.1 kHz and a faster response of 9.3 μs with a comparable effective coupling coefficient of 0.15 at the expense of a lower strain coefficient of 1.9 nm/V. The observed actuator performance was discussed in relation to the ceramic properties.     

变电站变压器运行损耗计算与智能降耗探讨

介绍了双绕组和三绕组变压器损耗计算方法,针对实例,从综合功率损耗角度出发,并考虑变压器并列运行的多种情况,分析了其运行中的损耗情况及降耗思路。     

边际网损系数法中的网损分摊调整方法

边际网损系数法由于能够反映各节点造成全网网损的微增成本信息,提供经济信号．已成为国外电力市场中最典型、最有应用前景的一种网损分摊方法。完全的边际网损系数法(FMLC)能提供最好的经济信号,但它不能保证所分摊的总网损与系统实际总网损一致,所以需要对该方法所分摊的网损量进行调整。本文应用比例法来调整网损分摊量。IEEE-14、IEEE-30和华东电网2243节点系统的算例表明：比例法合理地分摊了系统总网损,使之与实际总网损一致,并且,使用比例法后,保持了边际网损系数法的经济信号。     

金卤灯的钠损失

本文主要讨论了石英金卤灯里钠损失带来的危害以及钠损失产生的机理，并提出了几种减少钠损失的方法。钠损失往往会影响到电弧管里填充药丸的组成成分，药丸成分的改变会影响到灯的光电参数；钠损失还会造成灯寿命的降低。电弧管里钠损失主要是由于光电效应和高温下钠的扩散效应所引起的。     

高效电机损耗的控制

介绍了控制和降低铁耗、定子铜耗、转子损耗、负载杂散损耗及机械耗的措施及工艺手段,经实践验证表明介绍的措耗有利于提高电动机的效率,设计制造高效、超高效的电动机。     

用电管理中的降损措施

线损率是供电企业的主要经济技术考核指标之一。线损主要由两大部分组成 ,即 :技术线损和管理线损。线损理论计算工作是降损工作的基础。线损的统计分析 ,降损方案的确立和降损措施的采取都是以理论计算为依据的。研究降损措施是我们供电部门的一个重要课题。用电管理过程中的降损措施是降低线损的关键 ,主要有 :业扩过程中的降损措施 ;营业抄核收工作中的降损措施和电能计量管理中的降损措施。现分述如下。1　业扩过程中的降损措施业扩是我国电力工业营业工作中的一个习惯用语 ,它的主要含义是接受用户用电申请 ,根据电网实际情况 ,办理供…     

应用边际网损系数法分摊网损

网损的大小受各节点注入有功和无功功率的影响,以此为依据,提出了边际网损系数法,根据各节点注入功率对网损的影响程度分摊网损。综合考虑了有功、无功对系统网损的影响,并能向用户提供正确的经济信号,引导潮流向有利于网损减小的方向分布。     

高压电机铁心损耗和附加损耗的研究

用瞬态时步有限元法,应用场路结合法计算电机的铁心损耗和电机的空载附加损耗,以场路结合的思路为依据,用定子卡氏系数近似等效整个电机卡氏系数,通过实例验证用场路结合法计算铁耗及空载损耗的可行性,并简述了附加损耗试验方法。     

灯泡贯流式水轮机水力损失分析

对一台灯泡贯流式水轮机进行了全流道各过流部件的流场分析,探讨了各段流道内的水力损失在总损失中占有的比重以及产生的原因.分析结果表明,由于灯泡贯流式水轮机引水室形式的特殊性,几乎不能在导叶进口前提供环量,因此与有蜗壳的水轮机相比,这类水轮机的各过流部件在水力损失方面有不同的表现.活动导叶不仅作为调节流量的部件之一,也是转轮进口环量的提供者,导叶形状及与转轮的协联都对水轮机总损失有较大影响.