A study on characteristic indexesof railway ballast bed underhigh-frequency radar

Purpose–In this paper,a high-frequency radar test system was used to collect the data of clean ballast bed and fouled ballast bed of ballasted tracks,respectively,for a quantitative evaluation of the condition of railway ballast bed.Design/methodology/approach–Based on original radar signals,the time–frequency characteristics of radar signals were analyzed,five ballast bed condition characteristic indexes were proposed,including the frequency domain integral area,scanning area,number of intersections with the time axis,number of timedomain inflection points and amplitude envelope obtained by Hilbert transform,and the effectiveness and sensitivity of the indexes were analyzed.Findings–The thickness of ballast bed tested at the sleep bottom by high-frequency radar is up to 55 cm,which meets the requirements of ballast bed detection.Compared with clean ballast bed,the values of the five indexes of fouled ballast bed are larger,and the five indexes could effectively show the condition of the ballast bed.The computational efficiency of amplitude envelope obtained by Hilbert transform is 140 s$km
1,and the computational efficiency of other indexes is 5 s$km
1.The amplitude envelopes obtained by Hilbert transform in the subgrade sections and tunnel sections are the most sensitive,followed by scanning area.The number of intersections with the time axis in the bridge sections was the most sensitive,followed by the scanning area.The scanning area can adapt to different substructures such as subgrade,bridges and tunnels,with high comprehensive sensitivity.Originality/value–The research can provide appropriate characteristic indexes from the high-frequency radar original signal to quantitatively evaluate ballast bed condition under different substructures.

Local High-Frequency Heating in Electronics Technology

Modeling and investigation of HF electromagnetic heating in induction devices with unclosed magnetic circuit has allowed to optimize heating speed in local zones of formation of soldering connections and to improve their quality due to joint action of superficial effects and electromagnetic forces.For all magnetic materials is nonlinear decrease in heating power depending on frequency of HF.Installed the optimal parameters of HF heating for soldering electronics modules by inductor with open-ended magnetic conductor.

HPS Electronic Ballast Based on CIC-CPPFC Technique

Investigates the application of CIC CPPFC techniques to high pressure sodium(HPS) lamp electronic ballast. In order to ensure a unity power factor, different power electronic ballasts are studied by PSpice simulation. A dynamic model of HPS lamp with simple and accurate features is proposed for further study of characteristics. Experimental results verify the feasibility of HPS lamp operating at high frequency. It is shown that the presented electronic ballast has 0.99 power factor and 9% total harmonic distortion(THD).

Starting of HPS lamps driven by electronic ballast

A complete research of two different starting techniques for HPS lamps driven by electronic ballast is presented while a traditional starting technique based on the series resonant theory which is used widely for fluorescent lamps starting is analyzed in detail. An improved nth harmonic resonant technique is also simulated. Furthermore, a novel starting technique based on a pulse transformer is proposed, which still offer the automatic switch off capability. The differences between two starting techniques are explained. The experimental results from a lab prototype are used to verify the design.

A New-Style Two-Staged Dimmable Electronic Ballast

A two-staged electronic ballast with wide dimming range, high power factor(PF) and low electromagnetic interference(EMI) is presented. It changes the input voltage of the stage of power inverter for dimming control, so it overcomes some limitations of traditional electronic ballasts that use frequency variation. At the same time, the stage of power inverter runs under the soft-switching at the fixed switching frequency and reduces EMI greatly. Its principle and characteristic are analyzed in detail,and experimental and simulated results are obtained on a 40 W fluorescent lamp.

A Novel Single-Switch Single-Stage Electronic Ballast

A single-stage single-switch high- frequency electronic ballast topology is presented. The circuit topology is the integration of a buck power- factor-correction （PFC） converter and a class E resonant inverter with only one active power switch. The buck converter is operated in discontinuous conduction mode and at a fixed switching frequency, and constant duty cycle to achieve high power factor and it can be controlled easily. Detailed analysis of the operation and characteristics of the circuit is provided. Simulation results satisfy present standard requirements.

Dynamics of high-frequency modulated waves in a nonlinear dissipative continuous bi-inductance network

This paper presents intensive investigation of dynamics of high frequency nonlinear modulated excitations in a damped bimodal lattice. The effects of the dissipation are considered through a linear dissipation coefficient whose evolution in terms of the carrier wave frequency is checked. There appears that the dissipation coefficient increases with the carrier wave frequency. In the linear limit and for high frequency waves, study of the asymptotic behavior of plane waves reveals the existence of two additional regions in the dispersion curve where the modulational phenomenon is observed compared to the lossless line. Based on the multiple scales method exploited in the continuum approximation using an appropriate decoupling ansatz for the voltage of the two different cells, it appears that the motion of modulated waves is described by a dissipative complex Ginzburg–Landau equation instead of a Korteweg–de Vries equation. We also show that this amplitude wave equation admits envelope and hole solitons in the high frequency mode. From basic sources, we design a programmable electronic generator of complex signals with desired characteristics, which delivers signals exploited as input waves for all our numerical simulations. These simulations are performed in the LTspice software that uses realistic components and give the results that corroborate perfectly our analytical predictions.

基于平均电流控制的恒功率控制电路设计

为解决HID灯的老化及灯的伏安特性变化引起的功率漂移问题,基于Buck降压变换器的平均电流控制模式,设计并制作了一款具有恒功率控制能力的数字控制电子镇流器驱动电路,包含两个控制环路:内电流环路用于维持稳定驱动,外功率环路用于维持灯在其使用期间的功率恒定,并根据Buck降压变换器DCM模式下的小信号模型,以PI算法作为数字补偿器,完成补偿环路设计,保证电路输出稳定性。为抑制声共振,该电路结构采用三级式结构的电子镇流器,以低频方波驱动。设计和测试结果表明,该电子镇流器驱动电路可实现450 W的恒功率控制,误差值小于3%。该电子镇流器驱动电路结构简单,可靠性高,可适用于450 W HID灯驱动。

便携式低压钠灯电子镇流器设计

针对现有低压钠灯光源功耗高、输出稳定性差的问题,提出一种便携式低压钠灯电子镇流器设计方法。通过分析低压钠灯伏安特性曲线,对比现有典型低压钠灯镇流器的特点,根据低压钠灯工作原理设计相应的镇流电路。在电磁滤波的基础上,加入功率因数校正及恒功率控制电路以保证电路输出功率的稳定,加入LC谐振电路以保证电路输出频率的稳定,通过反馈控制实现电路的可靠工作。采用GP20NA-1型低压钠灯作为输出对象对低压钠灯电子镇流器输出电压、电流及低压钠灯辐射光谱进行验证,结果表明,低压钠灯电子镇流器输出功率稳定,常态下输出功率不大于20W,钠灯辐射光谱稳定于589.3nm,在光学计量、实验室照明等方面具有较高的应用价值。

气体放电灯电感镇流器与电子镇流器性能的比较

介绍了气体放电灯电感式镇流器和电子式镇流器的结构特点、性能特点及电子镇流器的应用举例,并对两种镇流器电网电压变化时的参数变化、发光效率等进行了对比分析。

高压钠灯电子镇流器的研究

简述了高压钠灯气体放电的工作特性 ,分析了高压钠灯电子镇流器的技术要求和实际电路拓扑 ,研制成功高功率因数 2 5 0W高压钠灯电子镇流器 。

无极灯系统的建模与分析

作为一种高光效、长寿命电光源,无极灯系统由作为供电电源的电子镇流器和发光泡体组成,电子镇流器的输出特性和发光泡体的阻抗特性之间存在着复杂的相互关系,共同决定了无极灯系统的启动速度和发光效率等性能。为了对无极灯系统进行建模与分析,本文首先搭建实验平台,对2.65MHz下发光泡体的阻抗特性进行了测量;其次,本文基于无极灯电子镇流器的电路拓扑,结合发光泡体的阻抗,通过数值拟合建立了电子镇流器串联谐振并联负载输出级参数与输出电压之间的关联数学模型,并对电子镇流器输出级的基本状态变量进行了分析,联立相应的边界条件得到了电子镇流器输出电压和电流的解析表达;最后,对电子镇流器输出电压进行了数值计算、Pspice仿真和实验验证,三者结果基本吻合,验证了所建系统模型和分析结果的准确性。

CLCL谐振软开关DC-AC变换器

针对大功率高压钠灯(HPS)电子镇流器的低电压大电流输出需求,本文提出一种CLCL谐振变换器,通过谐振实现零电压零电流开关(ZVZCS)及正弦波输出。根据变换器开关管实现软开关的条件,阐述了新电路的工作原理。提出了一种新的电路参数优化设计方法,使得ZVZCS条件下谐振器件上的电压应力最低。对新电路进行了理论和仿真分析。理论和仿真结果表明,新电路的开关管工作在零电压零电流或者准零电流开关状态。同时,输出端的电压、电流波形为正弦波,有效降低负载电流的波峰系数,延长负载使用寿命。研制了一台400V输入,100V/10A输出,开关频率为260kHz的DC-AC变换器样机。用来表明上述软开关实现策略的正确性,其最高满载效率可达99.1%。

电压间谐波分量对荧光灯闪变效应的研究

运用调制理论,对自激式电子镇流器荧光灯在间谐波导致的闪变电压下的功率波动进行理论分析,得到了在电源电压中含间谐波分量时荧光灯的功率响应,建立了荧光灯瞬时功率波动特征与间谐波特征之间的关系曲线。利用Matlab/Simulink软件对该研究对象进行的仿真和实验研究,验证了理论分析结果的正确性。理论分析和实验结果均表明电源电压中的间谐波分量可能导致荧光灯闪变,且闪变频率与间谐波造成的电压波动频率相同。荧光灯瞬时功率波动特征与间谐波特征之间关系的建立,有助于进一步对荧光灯在间谐波电压条件下的闪变效应进行评价方法研究,及其间谐波闪变限制标准的制定。

荧光灯照明光输出和闪烁的研究

对荧光灯照明光输出特性的研究和评价十分必要。闪烁指数是重要的评价指标。闪烁基频为工频频率的二倍 ,采用电感镇流时闪烁高达 10 %以上 ,降压或调光则急剧增加。采用电子镇流时 ,特别是输入功率因数有源校正方式 。

电子镇流器的拓扑结构、设计方法及其发展趋势

电子镇流器以其质量轻、体积小、高效节能等优良特性 ,成为电力电子技术在小功率范围内的典型应用。在回顾电子镇流器发展的基础上 ,全面介绍了电子镇流器的拓扑结构、性能差别、设计方法以及电子镇流器的发展趋势。

基于HID灯的电子镇流器控制技术综述

小型化、数字化、高效化和绿色化是镇流器发展方向,这对其控制技术提出了更高要求。在分析HID灯启动特性的基础上,归纳了点灯各阶段的基本控制方法。在对国内外研究成果系统化的基础上,分别从不同控制技术的工作原理、实现方法、性能指标等多方面进行了分析,为HID灯电子镇流器控制技术的研究和应用提供参考。

低频小功率金卤灯电子镇流器的研制

设计了一种适用于小功率金卤灯的低频高性能电子镇流器 ,在此基础上 ,试制成功 5 0W、 70W和 10 0W金卤灯电子镇流器 ,实验结果证明这种电子镇流器具有良好的工作性能。

低频方波金卤灯电子镇流器及其控制策略研究

该文提出了一种两级低频方波输出的高性能电子镇流器,作为MH灯工作电源。PFC级用于功率因数校正,DC/AC级结合了BUCK DC/DC变换器和全桥DC/AC逆变器的特点, 负载侧输出为低频方波,可有效克服MH灯声共振现象。采用分段控制方法实现镇流器与灯特性的配合,给出了其相应的控制策略。详细分析了它的工作原理和控制方法,给出了主要参数的计算方法。与传统三级低频方波电子镇流器相比,结构简单、所用器件少、可靠性高。电路仿真和实验结果验证了该方案是可行的。

基于单片机控制的35W汽车金卤灯电子镇流器

设计一种基于单片机控制的35W汽车金卤灯电子镇流器。采用变频技术,实现了金卤灯的快速启动;利用单端反激式变换器的输出尖峰电压,直接对高压点火电路充电,省去了传统高频变压器的专用点火绕组,从而减小了体积。经测试表明,该电子镇流器性能稳定,效率较高,能满足汽车前大灯照明要求。