T型客车充电器的基本原理BUSELECTRICALINST

T型客车充电器的基本原理ZHENGZHOURAILWAYVOCATIONAL&TECHNICALCOLLEGE客车电气装置/BUSELECTRICALINSTALLATIONSpeaker主讲人Zhangjia张嘉一、充电器基本原理从系统的安全性和可靠性来考虑，充电器是供电系统中最重要的设备之一，一旦充电器发生故障，蓄电池无法充电，电压会放到很低，有可能使本车挂在蓄电池上的所有设备都无法启动和工作。Consideredfromthesafetyandreliabilityofthesystem,thechargerisoneofthemostimportantequipmentinthepowersupplysystem,oncethechargerfails,thebatterycannotbecharged,thevoltagewillbeverylow,maymakethecar’salltheequipmentrelatingtothebatterycannotstartandwork.25T客车无论兼容供电还是DC600V供电，都需要充电器，将DC600V或AC380V变换成DC110V供给蓄电池和照明等负载。Whetherthe25TpassengercariscompatiblewithpowersupplyorDC600Vpowersupply,itneedsachargertoconvertDC600VorAC380VintoDC110Vtosupplybatteriesandlightingandotherloads.一、充电器基本原理PWM桥式DC/DC变换电路图PWMbridgeDC/DCconversioncircuitisshowninthefigure.充电器的输入隔离、滤波和缓冲电路与逆变器相同，逆变桥由4只IGBT组成，功率的传递靠高频变压器传递，变压器的输出经过高频整流和滤波后，供给直流负载和蓄电池。Theinputisolation,filteringandbufferingcircuitofthechargeristhesameasthatoftheinverter,theinverterbridgeiscomposedoffourIGBTs,andthepowertransmissionistransmittedbythehigh-frequencytransformer,andtheoutputofthetransformerisprovidedwiththeDCloadandthebatteryafterhigh-frequencyrectificationandfiltering.1.高频桥式逆变主电路V1～V4构成DC/DC变换的主电路，V1～V4的控制逻辑和变压器原副边电压波形如图4－18所示。V1toV4formthemaincircuitoftheDC/DCconversion.Figure4-18showsthecontrollogicofV1toV4andthevoltagewaveformoftheprimaryandsecondarysidesofthetransformer.t1～t2区间内，V1和V4导通，变压器原边电压为正相电压；Intherangeoft1~t2,V1andV4areswitchedon,andtheprimaryvoltageofthetransformerisapositivephasevoltage.t3～t4区间内，V2和V3导通，变压器原边电压为反相电压。Intherangeoft3tot4,V2andV3areon,andtheprimarysidevoltageofthetransformeristhereversephasevoltage.

2、电压变换的实现DC600V供电客车的DC/DC变换，主要是通过IGBT桥式逆变电路将直流600V电压变换成占空比可调的高频方波电压，经变压器隔离后整流滤波成DC110V电压。TheDC/DCconversionofDC600VpoweredpassengercarismainlythroughIGBTbridgeinvertercircuittoconvertDC600Vvoltageintohighfrequencysquarewavevoltagewithadjustabledutycycle,andthenrectifiedandfilteredintoDC110Vvoltageafterisolationbytransformer.兼容供电客车则是先将AC380V整流后，变成DC540V,然后采取与DC600V相同的DC/DC变换。ThecompatiblepowerpassengercarisfirstlyrectifiedAC380VintoDC540V,andthenadoptsthesameDC/DCconversionastheDC600V.所谓占空比是指一个半波内，驱动IGBT的脉冲宽度占整个半波周期的比例。Theso-calleddutycyclereferstotheproportionofthepulsewidthdrivingtheIGBTtothewholehalfwaveperiodwithinonehalfwave.为了调整输出电压，占空比是可变化的，属于脉冲宽度可调模式即PWM方式。Inordertoadjusttheoutputvoltage,thedutycycleisvariable,belongingtothepulsewidthadjustablemode,thatis,PWMmode.在这种控制方式下，脉冲的幅值是不变的，当负载发生变化时,依靠改变脉冲的宽度来保证输出电压的稳定;如果输入电压发生变化，也可以通过改变脉冲宽度来保证输出的稳定，如图所示。Inthiscontrolmode,theamplitudeofthepulseisconstant.Whentheloadchanges,thepulsewidthischangedtoensurethestabilityoftheoutputvoltage.Iftheinputvoltagechanges,youcanalsochangethepulsewidthtoensurethestabilityoftheoutput,asshowninthefigure.3、高频的影响采用20kHz的工作频率，主要是为了减小变压器、滤波器的体积。Theoperatingfrequencyof20kHzismainlyusedtoreducethevolumeoftransformersandfilters.变压器的原边或副边的感应电压有一个基本公式：Theinducedvoltageoftheprimaryorsecondarysideofthetransformerhasabasicformula:U=kfW1BS其中U为变压器线圈端电压，f为工作频率，W1为线圈匝数，B为磁通密度，S为磁路面积。WhereUisthetransformercoilendvoltage,fistheoperatingfrequency,W1isthenumberofcoilturns,Bisthemagneticfluxdensity,andSisthemagneticcircuitarea.从公式U=kfW1BS中可以看出，相同的输出电压和磁密时，当频率f提高，W1和S可相对减小，W1的减小即线圈绕组的匝数减少，亦即变压器的铜重可以减小；Itcanbeseenfromtheformulathatwhentheoutputvoltageandmagneticdensityarethesame,W1andScanberelativelyreducedwhenthefrequencyfisincreased,andthereductionofW1meansthatthenumberofturnsofthecoilwindingisreduced,thatis,thecopperweightofthetransformercanbereduced.S的减小即变压器铁心面积减小，亦即铁重减少，而铜线和铁心是决定变压器的主要有效体积和重量。ThereductionofSisthatthetransformercoreareaisreduced,thatis,theironweightisreduced,andthecopperwireandtheironcorearethemaineffectivevolumeandweightofthetransformer.当频率提高到20kHz时，变压器的铁心非常小，线圈匝数大幅减小。Whenthefrequencyisincreasedto20kHz,thecoreofthetransformerisverysmall,andthenumberofturnsofthecoilisgreatlyreduced.同样，高频输出脉冲（对应40kHz）的滤波电感和电容也明显减小，这就是高频化的效果。Similarly,thefilterinductanceandcapacitanceofthehigh-frequencyoutputpulsearealsosignificantlyreduced,whichistheeffectofhigh-frequency.

4、DC/DC变换器的功能和保护功能Function保护ProtectionDC/DC充电器的主要功能是将输入DC600V或AC380V变换成适合蓄电池充电和直流负载使用的DC110V，并在输入电压和负载变化时，保持输出稳定即稳压功能。ThemainfunctionoftheDC/DCchargeristoconverttheinputDC600VorAC380VintoDC110VsuitableforbatterychargingandDCload,andkeeptheoutputstablewhentheinputvoltageandloadchange.DC/DC充电器的输入保护和工作原理与逆变器相同。TheinputprotectionandworkingprincipleoftheDC/DCchargeristhesameasthatoftheinverter.5、限流定压充电功能充电器的输出电流分三个部分Theoutputcurrentofthechargerisdividedintothreesections部分向本车蓄电池充电,someofwhichchargethecarbattery,另有部分供给本车照明、控制等负载，someofwhichsupplythecarlighting,controlandotherloads,还有部分通过二极管向列车母线供电。andsomeofwhichsupplypowertothetrainbusthroughthediode.DC/DC充电器的工作原理图DC/DC变换器采用双闭环即电流环和电压环控制。TheDC/DCconverteradoptsdoubleclosedloopcontrol,thatis,currentloopandvoltageloop.图中，电压反馈靠电压传感器U/V输出测量信号，充电电流反馈靠电流传感器I2/V的输出信号,而电流传感器I1/V的反馈则提供输出总电流的检测信号。ThevoltagefeedbackdependsontheoutputmeasurementsignalofthevoltagesensorU,thechargingcurrentfeedbackdependsontheoutputsignalofthecurrentsensorI2,an