开关电源对设备EMI的影响及抑制方法

随着开关电源在各领域的广泛应用,由其导致的电磁发射问题也越来越引起关注。本文以开关电源的基本工作原理为基础,按其内部的各部分电路组成分别分析了电磁干扰的产生机理,并简要介绍了几种抑制由开关电源引起的电磁干扰的措施。     

开关电源模块可靠性的研究

本文分析了某军用开关电源模块的工作原理以及关键点波形,找出了开关电源模块中易于失效的关键元件,提出了目前开关电源发展所面临的可靠性寿命评价的关键问题。     

强电磁干扰下舰船通信的可靠性分析

为了提高强电磁干扰下舰船通信的可靠性,需要进行通信信号的抗干扰设计和信道均衡设计,提出一种基于自相关匹配滤波检测的强电磁干扰下舰船通信的可靠性优化方法。构建强电磁干扰下舰船通信的信号输出模型,提取强电磁干扰下舰船通信信号的输出谱特征,根据信道的冲激响应进行频谱畸变抑制,采用分数间隔均衡结合的方法进行强电磁干扰下舰船通信信道均衡设计,结合自相关匹配滤波检测方法实现强电磁干扰下舰船通信信号滤波检测和可靠性输出。仿真结果表明,采用该方法进行强电磁干扰下舰船通信的可靠性较好,抗干扰能力较强,输出的稳定性较好。     

机电产品电磁干扰综述

本文就电磁干扰对机电产品的影响进行综合性叙述,以便使读者对于电磁干扰的概况、作用及国内外有关电磁干扰的组织机构和试验标准有一初步的了解.     

军用微机电磁干扰的抑制技术和实践

由于航天产品电子设备之间存在着日益严重的电磁干扰,军用微机的电磁兼容性设计巳成为其一项设计指标和鉴定内容。本文从工程实践的再认识,以某型弹载计算机为例,介绍了一些抑制军用微机电磁干扰的技术。     

高频变压器饱和电流测试装置的设计

本文设计一种高频变压器饱和电流测试装置,解决开关电源设计过程中变压器饱和电流测试困难的问题,在开关电源设计的过程中方便工程师对高频变压器的评估,准确地设计出合理的高频变压器参数,缩短开发周期、提高所开发产品的可靠性。     

电磁干扰环境下产品失效机理分析

论述了电磁干扰环境对产品所产生的影响,阐述了在此环境下产品的失效模式,分析了在电磁干扰环境应力下产品功能失效的原因,指出了产品一般都会受到电磁波感应耦合、核电磁脉冲、静电失效、雷电电磁脉冲等干扰的影响作用,并针对性地提出了对产品进行有效防护的方法。     

变电站复杂电磁环境下的无线通信干扰抑制方法

变电站内的电磁环境复杂多变,存在各种电磁干扰,对无线通信产生了严重的影响。本文提出了一种基于独立成分分析算法的变电站无线网络设备电磁干扰识别与抑制方法。首先分析了变电站中电磁脉冲对通信链路的影响,然后提出干扰抑制方法。最后用所提出的方法对变电站的无线通信图像的干扰进行了抑制,抑制后的图像的误码率明显降低,说明了所提出方法对干扰抑制的有效性。     

磁光盘平面温度传感器的抗干扰设计

磁光盘的温度特性测量中，盘面温度的测量可采用平面温度传感器来感温。在磁光盘测试现场存在磁场干扰的情况下，还需考虑传感器的抗干扰设计。本文提示了能消除电磁干扰的传感器图形的最小磁链设计方法以及采用补偿器的方法和相应的传感器驱动电路，并举出实例说明这些措施有效地消除了传感器的电磁干扰。     

环境温度对开关电源适配器温升的影响及性能研究

为了确定出环境温度对开关电源适配器温升的影响规律,现提出一套行之有效的开关电源适配器温度试验方案。首先,介绍了试验流程。其次,从选取样品、测试环境搭建、试验方法三个方面入手,研究了试验前期准备。最后,从各样品温度实测值、环境温度差及对应的温度监测点温度差、计算△T/△Tamb的比值γ、统计分析值的规律等方面入手,对试验数据进行整理和分析。结果表明：本文所提出的开关电源适配器温度试验方案具有较高的可靠性和可行性,不仅可以保证最终试验结果的精确性,还能实现对相关温度试验极限值的精确化计算打下坚实的基础,完全符合实际应用需求。希望通过这次研究,为技术人员提供有效的借鉴和参考。     

A novel single-stage LED driver for energy-saving streetlight applications with interleaved power-factorcorrection

This paper proposes a novel single-stage light-emitting diode (LED) driver with interleaved power-factor corrections (PFC) suitable for energy-saving streetlight applications. The presented circuit combines an interleaved boost PFC converter with a half-bridge-type series-resonant converter cascaded with a full-bridge rectifier into a single-stage power-conversion topology. Two inductors in the interleaved boost PFC converter sub-circuit are designed to operate in discontinuous-conduction mode (DCM) in order to achieve input-current shaping, and the half-bridge-type series-resonant converter cascaded with a full-bridge rectifier is designed to obtain zero-voltage switching (ZVS) on two power switches to reduce their switching losses. The proposed driver features high power factor, low total-harmonic distortion (THD) of input current, and high circuit efficiency, all of which results in energy savings. A prototype driver is developed and implemented to supply a 165W-rated LED streetlight module with utility-line input voltages ranging from 210 V to 230 V. In addition, satisfactory experimental results have demonstrated the feasibility of the proposed LED driver.     

An isolated AC module for photovoltaic energy conversion

In this paper, an isolated ac module with pseudo dc-link and galvanic isolation is proposed for photovoltaic energy conversion. The studied grid-tie ac module can individually extract the maximum solar power from each photovoltaic panel and transfer to ac utility system. It consists of an interleaved active-clamping single-ended primary-inductive circuit (SEPIC) with a secondary voltage doubler, a full-bridge polarity selector operating under line frequency to achieve high efficiency. For the studied topology, key features such as reduced input current ripple, zero-voltage switching (ZVS) of primary switches, low reverse-recovery current of the output diodes, and lower switch voltage stress are obtained. Also, to reduce input current ripple, an interleaved control strategy is adopted. A simple control strategy is proposed to generate a rectified sinusoidal waveform voltage at the pseudo dc-link capacitors and achieve the high maximum power point tracking (MPPT) accuracy. The operation principles and design considerations of the studied ac module are analyzed and discussed. A prototype with 25–60 V dc input, 110 V/60 Hz ac output and 150 W power rating has been constructed for verifying the feasibility of the proposed ac module.     

Optimization of contactless transformer coupling transmission system by Taguchi method

A contactless transformer coupling (CTC) transmission system transmits electric energy via an alternating magnetic field through an air-gap. The transmitted power can be enhanced by the application of resonant effects. Transmitting and receiving coils are usually single layer solenoids with series capacitors, which, in combination, allow the receiving element to be tuned to the required transmitter frequency. An input DC source is used to obtain high-frequency AC signal through the standardized half-bridge DC/AC switching circuit. Further, the high-frequency signal passes through matching transformer and contactless coupling induction coil, which can be considered as an isolated input and output stage. Coupling must be tight to achieve high efficiency. This paper then applies the methods of Taguchi parameter design forthe contactless transformer coupling transmission system, which enhances the output voltage, loss factor, and output efficiency of the transmission system. The results of measurement verify the feasibility of this structure in the experiment.     

Shift to continuous operation of an air-cathode microbial fuel cell long-running in fed-batch mode boosts power generation

Microbial fuel cells (MFCs) which are operated in continuous mode are more suitable for practical applications than fed batch ones. The aim of the present study was to characterize an air-cathode MFC operating in continuous mode and to determine the intrinsic properties for suitable performance and scalability. Air-cathode MFCs were constructed from plexiglass with a total working volume of 220 mL. Zirfon® separator used in this MFC had cross section area of 100 cm². The air cathode MFCs were operated in fed-batch mode and then shifted to the continuous mode. To determine the behavior of anode and cathode in long term operation (274 days), their contribution in MFC performance was evaluated over time. Once the active biofilm was formed, power production and substrate consumption rate were significantly higher. The internal resistance increased with the passage of time. After stabilization of biofilm when the MFC was placed in close circuit by connecting an external resistance, the anode-reference and cathode-reference electrode behavior showed that anode potential is near to the bacterial cell inside potential. The maximum open circuit voltage achieved was 623 mV and the highest power and volumetric power density were 38.03 mW/m² and 1296 mW/m³, respectively.     

燃煤电厂PM_(2.5)减排技术与装备探讨

燃煤电厂在我国电力工业中占有很大的比重,其烟尘排放污染问题也尤其突出。大量燃煤烟尘的排放造成了严重的环境污染,特别是其中的细颗粒物PM2.5,能长期悬浮于大气中,对人类的健康造成了长期持续的危害,因此燃煤电厂PM2.5减排技术对于环境保护事业具有重要的意义和深远的影响,大力发展PM2.5减排技术与装备是电力行业大势所趋。     

Graphical Presentation of 50/60 Hz Magnetic Field Contours as an Engineering Tool for Minimizing ELF Fields

Summary Since IARC classified ELF magnetic field as Possibly Carcinogenic to Human the fear from 50/60 Hz magnetic field exposure had been increased to the state of public “panic”. Subsequently, environment quality preservation organizations increased their pressure on their government to adopt the “precautionary principle” and to reduce the allowable ELF Magnetic Field exposure to much lower values than are recommended by ICNIRP-1998. As an example the present Environmental Ministry in Israel recommendation is to lower the ELF Field exposure to 10 mG averaged over 24 h. As a result of this stringent exposure guideline imposed by the government, electrical engineers who are involved in the deployment and installation of large and medium electrical utilities, such as overhead power lines, transformers, UPS systems, electrical public transportation, switching stations, etc., are much more aware to the need to employ special measures and methods for reducing the magnetic fields that might be emitted from such utilities. There are few computer codes that are capable of analyzing with great accuracy magnetic and electric fields surrounding single phase and three phase electrical utilities in a 3-D system. The best presentations of the analysis results are by equi-value contours depicting electric and magnetic fields. This graphical presentation is a powerful design tool that enables better deployment and installation design aided to reduce the magnetic field emissions from high-power electrical utilities. This paper describes the various types of graphical presentations available for ELF field contours, the dependent and independent variants and parameters, magnetic field animation for optimization of power line installation and routing, and finally an example that demonstrates the usefulness of the graphical presentation tools.     

MODIFYING AUTOMATED PUMPING SAMPLERS FOR USE IN SMALL MOUNTAIN STREAMS1

ABSTRACT: Two modifications to automated pumping samplers improve discrete sampling during high flow events in small mountain streams. One modification entails mounting the intake nozzle on a bent, free-swinging metal rod supported in midstream. This allows sampling in midstream yet prevents the buildup of floatable organic debris that otherwise would cause the intake to fail. On the lower end of the rod, dynamic forces exerted by the stream keep the intake submerged over diverse flow conditions. The second modification consists of a magnetic switching device that automatically activates the pumping sampler at any preset stage on the rising limb of a storm hydrograph. The pumping sampler then remains on to collect one sample per hour which allows field crews sufficient time to change bottles before the sampler fills its 28-bottle capacity. This device improves the capability to sample frequently at fixed intervals, yet with minimal maintenance between runoff events. It also ensures sample collection during the rising limb of the hydrograph when flow and sediment concentrations are rapidly changing. Both modifications have improved data collection during periods of storm runoff.     

超低排放背景下煤电机组氨管控存在的问题及对策探析

近年来,我国大气污染防治成效显著,煤电机组超低排放政策实施对此做出了突出贡献。氮氧化物是煤电机组超低排放中的重要控制指标之一。然而,受现有氮氧化物排放监测和喷氨控制技术的精度、反馈时效等因素的限制,为提高脱硝效率保证性,电厂在实际运行中存在过量喷氨现象,未完全反应的氨进入大气后可能造成二次颗粒物增加。针对这一现象,本文回顾了我国火电行业氮氧化物排放标准和治理措施的演化及实施效果,对煤电机组氨排放现状和存在的问题进行了深入分析,提出在推进氮氧化物超低排放过程中应开展脱硝过量喷氨现状调研,鼓励企业开展脱硝系统优化,加强复杂烟气环境下氨监测技术研发,完善脱硝氨逃逸日常环境监管,推动氨排放全生命周期转化规律基础研究和大气环境效应评估,进一步提升煤电机组超低排放政策实施的综合环境效益,也对其他行业超低排放政策推进起到示范作用。