利德华福:品质奠基 大功率腾飞适逢其时——访北京利德华福电气技术有限公司副总工程师覃正清先生

随着高压变频技术日趋成熟和节能降耗、提高经济效益的市场需求越来越深化,高压变频技术正向着电压更高、功率更大、性能更优越的方向发展.大功率和超大功率高压变频器的市场前景日益被业内看好.如何解决大功率高压变频器在设计、生产、制造和应用中的技术难题成为打开国内大功率高压变频器市场的关键.     

高压变频器PLC监测保护系统的功能设计和实现

在工业应用中对高压大容量变频调速装置的需求越来越迫切,开发直接高压变频器,是一种技术含量高,开发难度大的高新技术.介绍了三电平IGCT直接高压变频器的工作原理和典型系统配置,总结了高压变频器的起动、停止和旁路等运行逻辑和联锁逻辑;设计了高压变频器的可编程序控制器(PLC)监测保护系统,阐述了系统的设计思想和实现过程中涉及的几个典型技术关键及其解决办法.系统设计具有一定的通用性,希望能够对高压变频器的设计、研制和使用提供参考.     

应用变频调速技术推进节能减排

20世纪80年代末期国外的交流变频调速技术渐渐兴起,进口产品价格昂贵,很难普及使用.国内近10年开始生产,随着国产高压变频器质量达到国际同类产品先进水平,价格也逐步下降, "十一五"期间国家计划节能20%,也促进了高压变频器在各行业的应用.虽然应用变频器可节电50%～50%,但变频器使用并不广泛,如全面推广应用变频技术,能最大限度地减少能源消耗和污染物排放,提高经济效益.文中介绍了变频调速技术在重点领域节电的显著效果及我国变频器产业的发展现状.     

高压变频器在输油管道上的应用

随着高压变频器技术的日益成熟,越来越多的高压变频器在生产实际中得到应用。通过系统构成、变频器性能特性、变频器工作原理和变频器操作及维护等环节的阐述,介绍了东临线惠民输油站两台罗宾康公司的空冷型完美无谐波系列高压变频器在管道输油上的应用情况。     

浅析高压变频器在锅炉风机中的应用

通过对高压变频器的工作原理和常用的控制方式、调速方案等主要技术特点的分析,结合高压变频器在本公司锅炉风机改造中的应用情况,指出高压变频器在实际应用中效果非常明显,在工业生产中具有较强的应用价值。     

能馈型高压变频器整流部分的研究

传统的级联型高压变频器只能电动运行,是电网污染的主要来源之一,为克服此不足,这里提出了一种应用三相PWM整流技术的级联型高压变频器.该变频器采用双闭环控制策略,具有输出电压恒定、单位功率因数运行等特点,可实现电能回馈电网,解决了电网的污染问题.通过实际应用显示,该变频器在降低谐波,抑制直流侧电容两端电压波动等方面有很大...     

利德华福：品质奠基 大功率腾飞适逢其时——访北京利德华福电气技术有限公司副总工程师覃正清先生

随着高压变频技术日趋成熟和节能降耗、提高经济效益的市场需求越来越深化,高压变频技术正向着电压更高、功率更大、性能更优越的方向发展。大功率和超大功率高压变频器的市场前景日益被业内看好。如何解决大功率高压变频器在设计、生产、制造和应用中的技术难题成为打开国内大功率高压变频器市场的关键。     

高压变频调节技术在锅炉风机改造上的应用

阐述了高压变频器在火电厂锅炉风机调节应用情况,着重介绍了盐城发电有限公司9号炉送引风机实施高压变频调节技术改造方案．高压变频器的技术特点以及高压变频器的运行调试和运行维护注意事项,分析了实施变频调节后节能经济效益。     

两种常见电压源型高压变频器的比较

1.引言 随着电气传动技术,尤其是变频调速技术的发展,作为大容量传动的高压变频调速技术也得到了广泛的应用。近年来,各种高压变频器不断出现,电压源型高压变频器具有运行稳定、调速范围宽、输出波形好、输入电流谐波含量低、功率因数高和效率高等优点,应用较为广泛。本文对三电平PWM变频器和单元串联多电平PWM变频器二种应用较为普遍的电压源型高压变频器进行分析比较,指出各自优缺点。 2.三电平PWM电压源型变频器 在PWM电压源型变频器中,当输出电压较高时,为了避免器件串联引起的动态均压问题,同时降低输出谐波和dv/dt,逆变器部分可以采用三电平方式,也称中心点钳位(Neutral Point Clamped:NPC)方式,如图1。逆变部分功率器     

ABB变频器在新型水煤浆气化高压煤浆泵变频传动中的应用

对ABB ACS800系列变频器在新型水煤浆加压气化技术高压煤浆泵变频传动系统中的应用情况进行了介绍,详细描述了变频器的选型、接线、调试及运行与维护.该变频器的应用提高了生产效率,降低了设备维护、运行费用.     

一种全光纤电流互感器运行性能现场测试方法

在综合分析全光纤电流互感器特点和运行中可能对其运行性能产生影响因素的基础上,提出了一种适用于工程现场的包括振动和VFTO等测试项目的全光纤电流互感器的测试方法,并对国内某220 kV智能变电站全光纤电流互感器进行了实际测试,证明全光纤电流互感器现场测试方法可行。     

Fabrication,modelling and use of porous ceramics for ultrasonic transducer applications

Porous ceramics are of interest for ultrasonic transducer applications. Porosity allows to decrease acoustical impedance, thus improving transfer of acoustical energy to water or biological tissues. For underwater applications, the d_hg_h figure of merit can also be improved as compared to dense materials. In the case of high frequency transducers, namely for high resolution medical imaging, thick film technology can be used. The active films are generally porous and this porosity must be controlled. An unpoled porous PZT substrate is also shown to be an interesting solution since it can be used in a screen-printing process and as a backing for the transducer. This paper describes the fabrication process to obtain such materials, presents microstructure analysis as well as functional properties of materials. Modelling is also performed and results are compared to measurements. Finally, transducer issues are addressed through modelling and design of several configurations. The key parameters are identified and their effect on transducer performance is discussed. A comparison with dense materials is performed and results are discussed to highlight in which cases porous piezoceramics can improve transducer performance, and improvements are quantified.     

Instrument current transducer for measurements in asymmetrical conditions in three-phase circuits with upper harmonics

The theme of the article is protection of electrical circuits against negative sequence currents both with sinusoidal and trapezoidal waveforms. The suggested solution is enhancement of instrument current transducers used in industrial relaying and control applications. The instrument negative sequence current transducer connected to Rogowski coils designed by the authors is presented in the article. To protect circuits with extremely non-sinusoidal currents (such as trapezoidal waveforms), instrument transducers with 2nd order low pass filter are suggested. In the presence of higher-order harmonics in the protected three-phase circuit the low pass filter will reduce the THD in the output voltage of instrument negative sequence current transducer (as compared to harmonics in currents of the protected circuit) and compensate for the differentiation effect typical of such transducer schemes.The paper may be of interest for investigators and engineers engaged in research, design and commissioning of protection and control equipment, current instrument and measurement devices used in industrial applications, and also for undergraduate and postgraduate students in electrical engineering.     

电力系统适用光学电流互感器的研究新进展

用于测量电力系统电流的光学电流互感器由于具有许多传统的电磁感应式电流互感器无法比拟的优点,具有广阔的应用前景。文中给出了基于法拉第磁光效应、以光纤为介质的光学电流互感器的基本原理和研究现状,重点论述为了加快实用化进程需要加以深入研究和解决的问题,包括新型的传感材料和传感头结构的研究、克服双折射效应、与光纤通信相结合等。     

The vibro-acoustic analysis of a matching layer attached on a 1–3 piezoelectric composite transducer

Journal of Electroceramics - A well-designed matching layer attached to a transducer is an effective method to obtain broad bandwidth. In practical applications, the optimal material parameters and...     

火电机组有功功率变送器应用分析

对火电机组常用的模拟式功率变送器进行了暂态特性分析,发现各种型号的模拟式功率变送器均不具备良好的暂态性能,在电网发生故障或扰动时其输出信号将发生畸变,可能导致机组汽门误动作。通过分析指出了响应时间过长与内部小电流互感器(TA)饱和是模拟式功率变送器输出波形畸变的原因。介绍了一种新型的功率变送装置,对功率变送器应用及改造中存在的问题进行了分析,指出当机组DEH系统中含有汽门快关功能时,须用新型的功率变送装置替代传统的功率变送器,以解决汽门快关误动作问题。     

浅谈防爆变频器的散热

文章介绍了几种用于防爆变频器的散热方法，并比较了它们性能及使用上的优劣。     

Electromechanical modeling and properties of the electret film EMFI

An electromechanical film can be manufactured with different thickness and elasticity. The thickness for sensor and actuator applications is typically between 30 and 70 μm. The film is modeled using a simplified structure, which shows the reciprocity of the sensor and actuator operation models. The value of the transducer constant depends on the ambient temperature and increases at higher temperatures. During aging the transducer constant begins to decrease permanently at 323 K, but some sensitivity remains even at 333 K. Corona charging that gives a sensitivity value ~200 pCN^-1 for HS01 type film is preferred over electron beam charging. The development of such films is aimed at sensor and actuator applications. An interesting field is the active control of sound where flat and efficient microphones and loudspeakers are needed     

Development of a new type of optical transducer for measuring faultcurrent

An optical current transducer has been developed capable of measuring current up to short-circuit currents of 50 kA. The optical current transducer is composed of a current measuring unit, an insulator with integral optical fibers, and an optical interface. The current measuring unit combines a winding with a magnetic iron core and a solenoid coil containing a Faraday sensor. The optical interface converts optical signals into electrical signals. Prototype optical current transducers have satisfied target performance requirements and have demonstrated the ability to maintain that level of performance in field applications     

三电平大功率通用变频器的研制

三电平逆变器的拓扑结构成熟,输出电压谐波含量低,所以广泛用于高电压大功率场合。在此,阐述了三电平大功率通用变频器的主回路设计、控制回路构成,以及控制软件编制;给出了一种基于滞环比较的中点电压平衡控制方法,以及该装置在工业现场运行的相关结果。通过对实际输出电压的频谱分析,得出了三电平逆变器输出电压的谐波特性,并概括了其谐波分布的一般规律。现场运行结果表明,该变频器的输出波形良好,性能可满足要求。