下載本文檔
版權(quán)說明:本文檔由用戶提供并上傳,收益歸屬內(nèi)容提供方,若內(nèi)容存在侵權(quán),請進(jìn)行舉報或認(rèn)領(lǐng)
文檔簡介
1、Thesolutionofcurrentdetectionusecurrenttransform電流的檢出利用電流變壓器(CT)可以檢出與負(fù)載電流成比率關(guān)係的的切換器初級圈電流(切換電流)。將切換電流轉(zhuǎn)成電壓,然後使用峰值檢波電路,獲取直流電壓。半波式檢波電路(Fig.1)適用於前向變換器(有半個週期無法檢出的問題)。檢波器電路為單純的電容器輸入型整流電路。由RC值決定檢出的反應(yīng)時間,此方式的反應(yīng)時間比並連電阻型慢,但是,此一方法可以檢出功率切換晶體或整流二極體故障所產(chǎn)生的過大電流。Fig.1CTandhalfbridgerectifiercircuit1/52020/4/13Thesolut
2、ionofcurrentdetectionusecurrenttransformCoreSize&MagnetizingcurrentforalltypeofcurrenttransformerIngeneral,forcurrenttransformers,Thelargertheinductance.Thesmallerthemagnetizingcurrent.Moreaccuratethemeasurement.Themagnetizingcurrentcomponentincreaseduringthepulsedurationandwillbesubtractedfromthequ
3、antitytobemeasured.Consequently,attheendoftheconductionpulse,themagnetizingcurrentshouldbesmallcomparedwiththemeasuredquantity.Forcurrentlimitapplication,magnetizingcurrentof10%isatypicaldesignlimit.2/52020/4/13ThesolutionofcurrentdetectionusecurrenttransformCurrentTransformerDesignProcedureStep1Cal
4、culate(orobserve)Peakprimarycurrent.Theslopedi/dt(i)onthetopthecurrentwaveformThiswillbeusedtocalculatetheminimumcurrenttransformerinductance.Step2CurrenttransformersecondaryvoltageSelectcurrenttransformersecondaryvoltageatthelimitingcurrentvalueTypically1Vincludingthediodedrop.Step3Ahigh-permeabili
5、ty(uofmaterial)sothatalargeinductancewillbeobtainedfortheminimumnumberofturns.2becauseL=uAN/lAlowremanenceBrThiswillensurethatthecorewillnotsaturateafterafewcyclesofoperation.Note:Thisrapidcorerestorationallowscloselyspacedforwardcurrentpulsestobemonitoredaccurately,withoutsaturationofcore.Clearly,t
6、hevalueofr1willbechosentogettherequiredminimumrecoverytime,andthevoltageratingofD1mustbeselectedtoblockthereverseflybackvoltageacrossr1showninFig2.Fig2.Recoverypathacrossr1Theresetvoltageandtimearedeterminedbyr1andtheresettimemustbelessthantheshortest“off“time.3/52020/4/13Thesolutionofcurrentdetecti
7、onusecurrenttransformUnidirectionalCurrentTransformerDesignExampleStep1CalculatePrimaryAmpere-Turns(NI)Intheexample,iftheprimarycurrentisXAinasingleturn.ThisgivesaprimarymagnetizingforceofXampere-turnsduetoforwardforcingcurrentthatflowsintheprimaryoftheforwardconvertertransformer.Step2DefineSecondar
8、yTurnsandCalculateSecondaryCurrentThisdesignwillusethepreferredwindingnotexceeding100turnsof#34AWGinsinglelayer(togiveasmallcoresizeandgoodhigh-frequencyperformance).Therefore,toprovideanequaldepolarizingmagneticforce0f10ampere-turns,thesecondarycurrentwillbe100mA.IfIp=10A、N1=1&N2=100Formula:Is=(N1/
9、N2)Ip(10A)=100mAN2IsStep3DefinetheRequiredSecondaryVoltageThesecondaryvoltagewillbe0.8V,madeupofthe0.6Vdiodedropandthe0.2VcurrentanaloguesignaldevelopedacrossR2.Consequently,with100turnsonthesecondaryandasignalcurrent-linkedturnontheprimary,thevoltagedropontheprimarywindingwillbe8mV.0.81/100=8mVThep
10、rimaryinsertionlossisthusverysmall.Forforwardconverterapplication,thepeakvalueofprimarycurrentatendofanperiodisrequiredcurrent-limitingvalue(thisindicatesthepeakcurrentflowingintheoutputinductor).Hencethesecondarycurrentmustreflectarisingcurrentduringtheandthis“on”periosetsalimitonthemagnetizingcurr
11、ent.apulse-by-pulsevoltageanalogueofthecurrentisgivenbythevoltageacrossR2.Henceafast-actingcurrentlimitmaybeintroducedatthispointinthecontrolcircuit,Usingthepeakanaloguevoltageinformation,orthecurrentsignalmaybeusedinacurrentmodecontrolcircuit.4/52020/4/13Thesolutionofcurrentdetectionusecurrenttrans
12、formStep4CheckMagnetizingCurrentCheckthatthemagnetizationcurrentisacceptablysmall.Tocalculatethemagnetizationcurrent,thesecondaryinductanceisrequired.IftheAlvalueofthecoreisknown,thentheinductancewillbecalculatedfromthebasicformula:L=N2AlIftheAlvalueofthecoreisnotknown,thentheinductancewillbecalcula
13、tedfromthe2basicformula:L=(roAeN)/leN=numberofsecondaryturns=ro7o=410r=permeabilityofcoreifr=7500L=31mHTheslopeofthemagnetizationcurrent,di/dt,canbecalculatedfrome=-Ldi/dtthereforedi/dt=e/Le=0.8Vdi/dt=25.8A/secIfprimarycurrent(Ip)attheendofthe10spulse,Imag=0.258mAThemagnetizationcurrenttransformstotheprimaryas25.8mA,anegligibleerrorin10A.Thesecondarycurrentwillbeatruetransformoftheprimarycurrentwithalossofonly1/4mAin100mAThisindicatesthatasmallercorecouldbeused,itcanbedifficulttowindthesecondaryonacoremuchsmallerthanthis.ThevalueoftheburdenresistorR2requiretodevelopthechosensig
溫馨提示
- 1. 本站所有資源如無特殊說明,都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請下載最新的WinRAR軟件解壓。
- 2. 本站的文檔不包含任何第三方提供的附件圖紙等,如果需要附件,請聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶所有。
- 3. 本站RAR壓縮包中若帶圖紙,網(wǎng)頁內(nèi)容里面會有圖紙預(yù)覽,若沒有圖紙預(yù)覽就沒有圖紙。
- 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
- 5. 人人文庫網(wǎng)僅提供信息存儲空間,僅對用戶上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理,對用戶上傳分享的文檔內(nèi)容本身不做任何修改或編輯,并不能對任何下載內(nèi)容負(fù)責(zé)。
- 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容,請與我們聯(lián)系,我們立即糾正。
- 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時也不承擔(dān)用戶因使用這些下載資源對自己和他人造成任何形式的傷害或損失。
最新文檔
- 超市裝修工程用工合同
- 裝修工程監(jiān)理合同范本
- 橡膠原料物流合同模板
- 學(xué)校裝修監(jiān)理服務(wù)合同
- 地震館改造外包合同樣本
- 技術(shù)轉(zhuǎn)讓居間合同格式
- 液態(tài)橡膠運(yùn)輸合同樣本
- 花卉綠植冷鏈運(yùn)輸合同范本
- 攝影棚裝飾項(xiàng)目管理合同
- 2024康健·寶盛廣場前期物業(yè)服務(wù)合同
- 新媒體寫作課件
- 老年學(xué)概論(第3版) 課件 第1、2章 人類個體和群體老齡化、老年學(xué)的學(xué)科性質(zhì)
- 2023年建隊日校長講話稿6篇
- 2024年河北省職業(yè)院校技能大賽生產(chǎn)事故應(yīng)急救援賽項(xiàng)樣題
- 第七章-外科感染病人的護(hù)理課件
- 空談?wù)`國實(shí)干興邦
- 護(hù)理人員緊急調(diào)配方案
- 電動車檢查表
- 新質(zhì)生產(chǎn)力解讀課件
- (修訂)高等教育心理學(xué)歷年考題與參考答案
- 幼兒園安全會議記錄20篇
評論
0/150
提交評論