在經歷2016年1月份股災的小伙伴們,想必知道了一個新的詞,那就是“熔斷”。對,就是在2016年股市開盤的1月4日至7日,中國股市經歷了過山車似的震蕩起伏。由于實施熔斷機制, 4天內連續引發4次熔斷,股市蒸發7.5萬億元,迫使滬深交易所深夜宣布,從1月8日起暫停實施熔斷機制。本文也來聊聊在新能源汽車中的高壓保護最后一道防火墻--熔斷(duan)器(熔斷器就是在所有其它保護都失效時,最后的有效保護器件)。

熔斷器的(de)應用(yong)領(ling)域(yu)非常廣泛,如前幾年火爆的(de)光(guang)伏市場等(deng),新能源汽車領(ling)域(yu)如直(zhi)流充電樁、DC、水暖PTC 充電機、風暖PTC、動(dong)力電池、維(wei)修開(kai)關、高(gao)壓箱、電動(dong)空調等(deng)涉及到高(gao)電壓需要保護的(de)地(di)方(fang),下文主要聊聊在PUD里面(mian)的(de)應用(yong)。

先來看看高壓配電盒,簡稱PDU(Power Distribution Unit),新能源車高壓系統解決方案中的高壓電源分配單元。通過母排及線束將高壓元器件電連接,為新能源汽車高壓系統提供充放電控制、高壓部件上電控制、電路過載短路保護、高壓采樣、低壓控制等功能等,保護和監控高壓系統的運行。PDU也能夠集成BMS主控、充電模塊、DC模塊、  PTC控制模塊等功能,與傳統PDU相比多了整車功能模塊,功能上更加集成化,結構上更復雜,具有水冷或是風冷等散熱結構。PDU配置靈活,可以根據客戶要求進行定制開發,能夠滿足不同客戶不同車型需求。BDU(Battery Disconnect Unit )電池包斷路單元,專為電池包內部設計,也是高壓配電盒的一種。

熔斷器熔斷原理介紹:

熔(rong)斷器(qi)作(zuo)用(yong):正(zheng)常(chang)情況下(xia),熔(rong)斷器(qi)在電(dian)(dian)路(lu)(lu)中起(qi)連接(jie)電(dian)(dian)路(lu)(lu)作(zuo)用(yong);非正(zheng)常(chang)(超(chao)負載)情況下(xia),熔(rong)斷器(qi)做(zuo)為電(dian)(dian)路(lu)(lu)中的安全(quan)(quan)保(bao)護(hu)(hu)元(yuan)件(jian),通過(guo)自身熔(rong)斷安全(quan)(quan)切斷并(bing)保(bao)護(hu)(hu)電(dian)(dian)路(lu)(lu)。熔(rong)斷器(qi)的作(zuo)用(yong)是保(bao)護(hu)(hu)電(dian)(dian)氣設備,防止電(dian)(dian)氣設備因過(guo)載造成損(sun)壞。

熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)(qi)(qi)的(de)(de)熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)是熔(rong)(rong)體被過電流釋放的(de)(de)熱能(neng)(neng)所熔(rong)(rong)化(hua)而造(zao)成(cheng)的(de)(de),而能(neng)(neng)夠熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)(qi)(qi)的(de)(de)能(neng)(neng)量就是熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)(qi)(qi)的(de)(de)熔(rong)(rong)化(hua)熱能(neng)(neng)值I*I*t(Q=I*I*t*R,R是定(ding)值),理(li)論上說,只(zhi)要(yao)熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)(qi)(qi)熔(rong)(rong)化(hua)所需要(yao)的(de)(de)能(neng)(neng)量大于瞬間脈沖電流所釋放的(de)(de)能(neng)(neng)量,熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)(qi)(qi)就不會被沖斷(duan)(duan)(duan)(duan)(duan),也就是熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)(qi)(qi)可以抵抗這(zhe)種脈沖的(de)(de)沖擊,一般(ban)慢熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)型熔(rong)(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)(qi)(qi)都具備(bei)這(zhe)種特(te)性(xing)。

那么抵抗(kang)過一次(ci)瞬間脈沖(chong)(chong)(chong)(chong)(chong)(chong)的(de)(de)(de)(de)熔(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)有沒有發生什么變(bian)化呢(ni)?那就(jiu)(jiu)要(yao)看它(ta)受(shou)脈沖(chong)(chong)(chong)(chong)(chong)(chong)的(de)(de)(de)(de)傷(shang)(shang)害(hai)有多(duo)(duo)大(da)了。如果該脈沖(chong)(chong)(chong)(chong)(chong)(chong)能(neng)量(liang)遠小(xiao)于(yu)熔(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)熔(rong)化熱(re)能(neng),熔(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)受(shou)到(dao)的(de)(de)(de)(de)沖(chong)(chong)(chong)(chong)(chong)(chong)擊(ji)很小(xiao),那么熔(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)就(jiu)(jiu)可以接(jie)受(shou)許許多(duo)(duo)多(duo)(duo)次(ci)沖(chong)(chong)(chong)(chong)(chong)(chong)擊(ji)而不被沖(chong)(chong)(chong)(chong)(chong)(chong)斷(duan)(duan)(duan)(duan)(duan),反之如果脈沖(chong)(chong)(chong)(chong)(chong)(chong)能(neng)量(liang)接(jie)近熔(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)熔(rong)化熱(re)能(neng),熔(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)被沖(chong)(chong)(chong)(chong)(chong)(chong)擊(ji)一次(ci)受(shou)到(dao)的(de)(de)(de)(de)損(sun)傷(shang)(shang)很大(da),那么它(ta)就(jiu)(jiu)可能(neng)受(shou)不起第二次(ci)的(de)(de)(de)(de)沖(chong)(chong)(chong)(chong)(chong)(chong)擊(ji)了,也就(jiu)(jiu)是說:熔(rong)斷(duan)(duan)(duan)(duan)(duan)器(qi)在經(jing)受(shou)每一次(ci)脈沖(chong)(chong)(chong)(chong)(chong)(chong)的(de)(de)(de)(de)沖(chong)(chong)(chong)(chong)(chong)(chong)擊(ji)后都會受(shou)到(dao)一定程度的(de)(de)(de)(de)損(sun)傷(shang)(shang),即(ji)它(ta)的(de)(de)(de)(de)耐脈沖(chong)(chong)(chong)(chong)(chong)(chong)能(neng)力(li)有所減弱或I*I*t有所降(jiang)低(di)(di),減弱或降(jiang)低(di)(di)的(de)(de)(de)(de)程度跟(gen)脈沖(chong)(chong)(chong)(chong)(chong)(chong)的(de)(de)(de)(de)能(neng)量(liang)成(cheng)正比。

我們要(yao)使(shi)熔(rong)斷(duan)器(qi)能夠承受多次瞬間脈沖(chong)(chong)(chong)的(de)(de)(de)(de)(de)(de)沖(chong)(chong)(chong)擊,必須要(yao)在熔(rong)斷(duan)器(qi)的(de)(de)(de)(de)(de)(de)I*I*t和脈沖(chong)(chong)(chong)能量(liang)(liang)間放(fang)足夠的(de)(de)(de)(de)(de)(de)余量(liang)(liang),不(bu)同的(de)(de)(de)(de)(de)(de)電(dian)器(qi)產(chan)品(pin)由于使(shi)用壽命和開關頻率不(bu)同,需要(yao)承受脈沖(chong)(chong)(chong)的(de)(de)(de)(de)(de)(de)次數也不(bu)同,所以(yi)熔(rong)斷(duan)器(qi)的(de)(de)(de)(de)(de)(de)供應商應該提供相應的(de)(de)(de)(de)(de)(de)參考(kao)數據,即對(dui)應不(bu)同脈沖(chong)(chong)(chong)次數,需要(yao)選擇熔(rong)斷(duan)器(qi)的(de)(de)(de)(de)(de)(de)I*I*t對(dui)脈沖(chong)(chong)(chong)能量(liang)(liang)的(de)(de)(de)(de)(de)(de)不(bu)同倍數,這里僅是粗略的(de)(de)(de)(de)(de)(de)估算(suan),準確的(de)(de)(de)(de)(de)(de)選擇必須要(yao)通過具體數據的(de)(de)(de)(de)(de)(de)計(ji)算(suan)來得到(dao)。 

熔斷器的三個關鍵參數:

1. 額定(ding)電壓(ya);2. 定(ding)電流(liu);3. 極限分斷(duan)(duan): 這是(shi)(shi)(shi)熔(rong)斷(duan)(duan)器(qi)在(zai)故障條件(jian)下(xia)(xia)能可靠的分斷(duan)(duan)最大(da)短(duan)路電流(liu),它是(shi)(shi)(shi)熔(rong)斷(duan)(duan)器(qi)的主要技(ji)術指標(biao)之(zhi)一(其實也是(shi)(shi)(shi)很多技(ji)術人員忽略的地方)。下(xia)(xia)圖的產品為電壓(ya)1000VDC, 200A, 分斷(duan)(duan)能力IR為50KA,三者的關系(xi)見下(xia)(xia)文。

以上僅是針對在PDU中熔斷器的部分見解與認知。熔斷器在直流充電樁、DC、水暖PTC 充電機、風暖PTC、動力電池、維修開關、電動空調等場景應用不盡相同,電流持續時間,抗震性能,工作環境要求,海拔高度,壽命要求等,需要設計選型根據不同的工況來綜合考慮,本文不作為您設計與選型最終參考。

轉載：【電動汽車(che)資源網EV江湖 Bentty李清(qing)】