0 引言

高(gao)(gao)壓(ya)開(kai)關(guan)主要(yao)是用(yong)于關(guan)合及開(kai)斷(duan)(duan)正常(chang)(chang)的(de)(de)或有(you)故障的(de)(de)電(dian)(dian)路?也(ye)可以用(yong)來隔(ge)離(li)高(gao)(gao)壓(ya)電(dian)(dian)源?它是保證電(dian)(dian)力(li)系(xi)統(tong)安全運行的(de)(de)重(zhong)(zhong)要(yao)設備。由于高(gao)(gao)壓(ya)開(kai)關(guan)在(zai)電(dian)(dian)力(li)系(xi)統(tong)中(zhong)(zhong)肩負著(zhu)控制(zhi)和保護的(de)(de)雙(shuang)重(zhong)(zhong)任務?其性能的(de)(de)可靠(kao)性程(cheng)度將對電(dian)(dian)力(li)系(xi)統(tong)的(de)(de)安全運行起著(zhu)至關(guan)重(zhong)(zhong)要(yao)的(de)(de)作(zuo)用(yong)?所以對高(gao)(gao)壓(ya)開(kai)關(guan)的(de)(de)各個參(can)(can)數指標的(de)(de)可靠(kao)性進行評(ping)估十分必(bi)要(yao)?其中(zhong)(zhong)導電(dian)(dian)回(hui)路電(dian)(dian)阻(zu)即接觸電(dian)(dian)阻(zu)是這(zhe)些參(can)(can)數中(zhong)(zhong)*重(zhong)(zhong)要(yao)的(de)(de)參(can)(can)數之一(yi)。高(gao)(gao)壓(ya)開(kai)關(guan)的(de)(de)觸頭(tou)接觸面經過(guo)多次的(de)(de)開(kai)斷(duan)(duan)、關(guan)合電(dian)(dian)流后逐漸(jian)被電(dian)(dian)磨(mo)損(sun)?導致接觸電(dian)(dian)阻(zu)增大?這(zhe)對高(gao)(gao)壓(ya)開(kai)關(guan)的(de)(de)開(kai)斷(duan)(duan)和導電(dian)(dian)性能都會產生非(fei)常(chang)(chang)不(bu)利的(de)(de)影響。而(er)通(tong)過(guo)測量(liang)接觸電(dian)(dian)阻(zu)阻(zu)值可以估計出觸頭(tou)的(de)(de)磨(mo)損(sun)程(cheng)度和回(hui)路的(de)(de)接觸狀況。

接(jie)(jie)觸(chu)(chu)電(dian)阻(zu)(zu)一般(ban)是(shi)微(wei)歐級的(de)(de)(de)(de)(de)小(xiao)(xiao)電(dian)阻(zu)(zu)。目前*常用(yong)(yong)的(de)(de)(de)(de)(de)接(jie)(jie)觸(chu)(chu)電(dian)阻(zu)(zu)測(ce)量(liang)方法(fa)是(shi)直(zhi)流(liu)電(dian)壓(ya)(ya)降法(fa)?即向高(gao)壓(ya)(ya)開關(guan)(guan)通(tong)入100 A 以上(shang)的(de)(de)(de)(de)(de)恒(heng)定(ding)大電(dian)流(liu)?測(ce)量(liang)高(gao)壓(ya)(ya)開關(guan)(guan)兩端的(de)(de)(de)(de)(de)電(dian)壓(ya)(ya)降?根據歐姆定(ding)律計算(suan)出(chu)高(gao)壓(ya)(ya)開關(guan)(guan)的(de)(de)(de)(de)(de)接(jie)(jie)觸(chu)(chu)電(dian)阻(zu)(zu)值。然而(er)?在(zai)長時間通(tong)入恒(heng)定(ding)大電(dian)流(liu)時?容易使觸(chu)(chu)頭過(guo)度發熱和(he)加(jia)速氧化?從而(er)引起接(jie)(jie)觸(chu)(chu)電(dian)阻(zu)(zu)測(ce)量(liang)值的(de)(de)(de)(de)(de)附加(jia)誤差(cha)?而(er)且通(tong)常使用(yong)(yong)的(de)(de)(de)(de)(de)大電(dian)流(liu)發生器體積和(he)重量(liang)都比(bi)較大（一般(ban)在(zai)幾千(qian)克到十幾千(qian)克左右）?不利于攜(xie)帶和(he)現(xian)場測(ce)試(shi)使用(yong)(yong)。因此?設計一種既能保(bao)證在(zai)接(jie)(jie)觸(chu)(chu)電(dian)阻(zu)(zu)上(shang)引起的(de)(de)(de)(de)(de)附加(jia)電(dian)阻(zu)(zu)非(fei)常小(xiao)(xiao)、又能夠減(jian)小(xiao)(xiao)測(ce)試(shi)儀器的(de)(de)(de)(de)(de)體積和(he)重量(liang)的(de)(de)(de)(de)(de)新(xin)型(xing)電(dian)源工作方式(shi)?有著重要的(de)(de)(de)(de)(de)現(xian)實意(yi)義。

筆者采用(yong)脈(mo)沖電源測量(liang)接(jie)觸電阻、智能化嵌入式(shi)系統采集和處理數據的(de)方法?設(she)計出一(yi)種在**度(du)和穩定度(du)都滿足要求的(de)前提下便于(yu)攜帶和現場使(shi)用(yong)的(de)高壓開(kai)關接(jie)觸電阻測試(shi)儀。

1 高壓開關接(jie)觸(chu)電阻測試儀原理

脈沖電(dian)(dian)源(yuan)接觸電(dian)(dian)阻(zu)測量方法即(ji)采用脈沖電(dian)(dian)源(yuan)對電(dian)(dian)容(rong)充電(dian)(dian)?然后該充電(dian)(dian)電(dian)(dian)容(rong)對串聯的二階(jie)電(dian)(dian)路(lu)進行放(fang)電(dian)(dian)?產生的沖擊電(dian)(dian)流即(ji)為(wei)脈沖電(dian)(dian)源(yuan)的脈沖輸(shu)出電(dian)(dian)流?測量原理框(kuang)圖如(ru)圖1所示（虛線(xian)框(kuang)內為(wei)脈沖電(dian)(dian)源(yuan)部分(fen)）。測量過(guo)程(cheng)(cheng)主要分(fen)為(wei)充電(dian)(dian)過(guo)程(cheng)(cheng)、放(fang)電(dian)(dian)過(guo)程(cheng)(cheng)、數(shu)(shu)據(ju)采集處理過(guo)程(cheng)(cheng)（數(shu)(shu)據(ju)采集是在放(fang)電(dian)(dian)過(guo)程(cheng)(cheng)中完(wan)成的）以及結果顯示。

圖1中?首先由 LPC2378控(kong)(kong)制充(chong)電(dian)(dian)(dian)(dian)(dian)回路(lu)繼電(dian)(dian)(dian)(dian)(dian)器(qi)開(kai)(kai)(kai)(kai)關(guan)(guan) K1 閉合?放電(dian)(dian)(dian)(dian)(dian)回路(lu)可控(kong)(kong)硅(gui)開(kai)(kai)(kai)(kai)關(guan)(guan) K2 斷(duan)開(kai)(kai)(kai)(kai)?使(shi)得可控(kong)(kong)電(dian)(dian)(dian)(dian)(dian)源(yuan)給電(dian)(dian)(dian)(dian)(dian)容器(qi) C 充(chong)電(dian)(dian)(dian)(dian)(dian)?充(chong)電(dian)(dian)(dian)(dian)(dian)完成后?LPC2378控(kong)(kong)制充(chong)電(dian)(dian)(dian)(dian)(dian)回路(lu)繼電(dian)(dian)(dian)(dian)(dian)器(qi)開(kai)(kai)(kai)(kai)關(guan)(guan) K1 斷(duan)開(kai)(kai)(kai)(kai)?放電(dian)(dian)(dian)(dian)(dian)回路(lu)可控(kong)(kong)硅(gui)開(kai)(kai)(kai)(kai)關(guan)(guan) K2 閉合?此時電(dian)(dian)(dian)(dian)(dian)容器(qi) C 放電(dian)(dian)(dian)(dian)(dian)產生一(yi)個(ge)沖(chong)擊電(dian)(dian)(dian)(dian)(dian)流(liu)至高壓開(kai)(kai)(kai)(kai)關(guan)(guan)和分(fen)流(liu)器(qi)?同時 LPC2378通(tong)過(guo)A／D轉換器(qi)連(lian)續采集(ji)分(fen)流(liu)器(qi)兩端電(dian)(dian)(dian)(dian)(dian)壓和高壓開(kai)(kai)(kai)(kai)關(guan)(guan)兩端電(dian)(dian)(dian)(dian)(dian)壓?并(bing)通(tong)過(guo)軟件編程來判斷(duan)放電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)是(shi)否達(da)到峰值(zhi)。

峰值(zhi)電(dian)(dian)壓(ya)(ya)是通過采集(ji)高壓(ya)(ya)開關兩(liang)端的電(dian)(dian)壓(ya)(ya)得到(dao)的?峰值(zhi)電(dian)(dian)流是通過采集(ji)分流器(qi)兩(liang)端的峰值(zhi)電(dian)(dian)壓(ya)(ya)除(chu)以分流器(qi)電(dian)(dian)阻得到(dao)的?這樣?就(jiu)可得到(dao)高壓(ya)(ya)開關接觸(chu)電(dian)(dian)阻

兩端的電壓和(he)通(tong)過的電流?進而得到高(gao)壓開(kai)關的接(jie)觸電阻阻值。

電(dian)(dian)流(liu)(liu)(liu)、電(dian)(dian)壓(ya)信(xin)號采集(ji)部(bu)分(fen)均使(shi)用(yong)了四端(duan)(duan)(duan)子(zi)(zi)接(jie)(jie)線(xian)技術：使(shi)用(yong)2對測(ce)試(shi)夾(jia)測(ce)量高壓(ya)開關(guan)兩(liang)端(duan)(duan)(duan)電(dian)(dian)壓(ya)?電(dian)(dian)流(liu)(liu)(liu)引線(xian)接(jie)(jie)在(zai)導(dao)電(dian)(dian)桿外(wai)側(ce)（圖1中2和2＇ 點(dian)處(chu)）?電(dian)(dian)壓(ya)引線(xian)接(jie)(jie)在(zai)導(dao)電(dian)(dian)桿內側(ce)（圖1中1和1＇ 點(dian)處(chu)）；測(ce)量放電(dian)(dian)回路電(dian)(dian)流(liu)(liu)(liu)時?采用(yong)具有(you)(you)4個(ge)端(duan)(duan)(duan)子(zi)(zi)的(de)(de)標(biao)準電(dian)(dian)阻－－－分(fen)流(liu)(liu)(liu)器(qi)?分(fen)流(liu)(liu)(liu)器(qi)中2個(ge)大的(de)(de)端(duan)(duan)(duan)子(zi)(zi)是電(dian)(dian)流(liu)(liu)(liu)端(duan)(duan)(duan)子(zi)(zi)?與被測(ce)高壓(ya)開關(guan)串聯?2個(ge)小的(de)(de)端(duan)(duan)(duan)子(zi)(zi)是電(dian)(dian)壓(ya)端(duan)(duan)(duan)子(zi)(zi)?通過采集(ji)這2個(ge)小的(de)(de)端(duan)(duan)(duan)子(zi)(zi)之(zhi)間的(de)(de)電(dian)(dian)壓(ya)信(xin)號可確定放電(dian)(dian)回路的(de)(de)電(dian)(dian)流(liu)(liu)(liu)。采用(yong)四端(duan)(duan)(duan)子(zi)(zi)接(jie)(jie)線(xian)技術可有(you)(you)效地消(xiao)除(chu)引線(xian)電(dian)(dian)阻和測(ce)試(shi)夾(jia)接(jie)(jie)觸電(dian)(dian)阻的(de)(de)影響?提高測(ce)量精度。

2 高壓(ya)開關(guan)接觸電阻測試儀的(de)設計

為了提高(gao)測(ce)量精度和儀器的(de)(de)抗(kang)干擾(rao)能(neng)力?該(gai)測(ce)試儀在(zai)硬件上(shang)選用的(de)(de)是(shi)飛(fei)利浦公(gong)司生產的(de)(de) ARM7核的(de)(de)工業級32位處(chu)理器 LPC2378?LPC2378具(ju)有512KB 的(de)(de)片內 FLAS H?*高(gao)頻率(lv)可(ke)達72 M Hz；在(zai)軟(ruan)件上(shang)采用平滑濾(lv)波方法(fa)?以消除部(bu)分受干擾(rao)的(de)(de)數據。

2．1 硬件(jian)結(jie)構

該測(ce)試儀的硬(ying)件電(dian)路主要分(fen)(fen)為(wei)2個部分(fen)(fen)：一是脈(mo)沖電(dian)源(yuan)部分(fen)(fen)?主要包(bao)括(kuo)充(chong)、放電(dian)回路和可控硅及繼電(dian)器等；二是以 LPC2378為(wei)中心的數據采集部分(fen)(fen)?主要包(bao)括(kuo)信號調理、A／D 轉換、信號隔離、人機接口等電(dian)路。

（1） 脈沖電源(yuan)部分

如圖2所示(shi)?220V 交流(liu)電(dian)(dian)(dian)(dian)(dian)先經過隔(ge)離(li)變(bian)壓(ya)器(qi)進入到(dao) J1 兩端(duan)?然后經二(er)極管 D0 進行半波整流(liu)?通過 LPC2378的(de) P2．1口控制繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)器(qi)開(kai)關(guan)(guan) K1 對電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容 C1 進行充電(dian)(dian)(dian)(dian)(dian)。二(er)極管 D2 用(yong)來限(xian)制 C1 放電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)方向(xiang)?防止 C1 被(bei)反向(xiang)充電(dian)(dian)(dian)(dian)(dian)。電(dian)(dian)(dian)(dian)(dian)阻(zu) R1 為(wei)充電(dian)(dian)(dian)(dian)(dian)限(xian)流(liu)電(dian)(dian)(dian)(dian)(dian)阻(zu)。充電(dian)(dian)(dian)(dian)(dian)過程中?繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)器(qi)開(kai)關(guan)(guan) K1 閉(bi)合?可控硅(gui)開(kai)關(guan)(guan) K2 斷(duan)開(kai)?當 C1 兩端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)達到(dao)所需的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)值時?通過 A／D 轉換器(qi)不斷(duan)檢測分壓(ya)電(dian)(dian)(dian)(dian)(dian)阻(zu) R3 兩端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)以判斷(duan)充電(dian)(dian)(dian)(dian)(dian)是否(fou)完成(cheng)。斷(duan)開(kai)繼(ji)(ji)電(dian)(dian)(dian)(dian)(dian)器(qi)開(kai)關(guan)(guan) K1、閉(bi)合可控硅(gui)開(kai)關(guan)(guan) K2?則 C1 便開(kai)始(shi)(shi)對后面的(de)電(dian)(dian)(dian)(dian)(dian)路(lu)進行放電(dian)(dian)(dian)(dian)(dian)。放電(dian)(dian)(dian)(dian)(dian)開(kai)始(shi)(shi)的(de)同時進行分流(liu)器(qi)和(he)被(bei)測高壓(ya)開(kai)關(guan)(guan)兩端(duan)電(dian)(dian)(dian)(dian)(dian)壓(ya)信號的(de)采集任(ren)務。

（2） 數據采(cai)集部分

由于分流(liu)器(qi)兩(liang)端電壓信號(hao)為毫(hao)伏級?為減少測量(liang)誤差?選用 INA114儀用放(fang)大器(qi)?INA114具有高(gao)輸入(ru)阻抗、低輸出阻抗、低溫漂、高(gao)共模(mo)抑制能力、低

失調電壓、高穩定增益等特點(dian)。A／D 轉換器選用(yong)(yong)12位的(de)(de)逐次逼近型 MCP3204?MCP3204具有4個通道?可分(fen)別檢(jian)測分(fen)壓電阻 R3 兩(liang)端電壓、分(fen)流器兩(liang)端電 壓 和(he) 高 壓 開 關 兩(liang) 端 電 壓?采 樣 速 率(lv) 達100kbit／s。信號隔離采用(yong)(yong)常用(yong)(yong)的(de)(de) T LP512隔離芯(xin)片。人機接口電路選用(yong)(yong) HG240128液晶顯示模(mo)塊(kuai)?該模(mo)塊(kuai)支持字(zi)符顯示?帶溫(wen)度補償自(zi)動調解背光?抗干擾性較強?有240×128個點(dian)?可直觀(guan)顯示測量結(jie)果。

2．2 軟件設(she)計

由于(yu)在(zai)短時間內(nei)連續(xu)采集數據?還要處(chu)理采集的(de)數據、判斷電流、電壓峰值?所以軟件設(she)計是該測試儀的(de)一個(ge)重要部分?其主程(cheng)序流程(cheng)如(ru)圖3所示。

主(zhu)程序(xu)的(de)功能主(zhu)要(yao)是進行脈沖電源的(de)充(chong)放電控制?調用(yong)各子程序(xu)模塊并進行數據處理得出所要(yao)測量(liang)的(de)高壓(ya)開關接(jie)觸(chu)電阻阻值(zhi)。

（1） 初(chu)始(shi)(shi)化(hua)：包括 CPU 的輸入、輸出端口(kou)初(chu)始(shi)(shi)化(hua)、液(ye)晶顯示初(chu)始(shi)(shi)化(hua)以及定(ding)時器初(chu)始(shi)(shi)化(hua)等。

 （2） 采(cai)集信號：不斷(duan)(duan)采(cai)集分流器(qi)、高(gao)壓開關（斷(duan)(duan)路(lu)器(qi)）兩端電(dian)(dian)壓?進行(xing) A／D 轉換后(hou)送(song)入 CPU?由于要判斷(duan)(duan)電(dian)(dian)流峰值?所以放(fang)電(dian)(dian)過程中要連續采(cai)集20次(ci)

分流器兩端電(dian)壓?采(cai)集次數(shu)(shu)主(zhu)要(yao)與 CPU 頻率(lv)(lv)和A／D轉換頻率(lv)(lv)有關?采(cai)集次數(shu)(shu)越多?結果(guo)越**。采(cai)集的數(shu)(shu)據暫(zan)時存(cun)儲以供數(shu)(shu)據處(chu)理用。

（3） 處理數(shu)(shu)(shu)據：對采集的數(shu)(shu)(shu)據進行平滑濾波處理?然后進行數(shu)(shu)(shu)據轉換處理?*后得到放電(dian)(dian)回(hui)路中的峰值電(dian)(dian)流(liu)和峰值電(dian)(dian)流(liu)時刻高壓(ya)開關兩端電(dian)(dian)壓(ya)值?進而(er)得到高壓(ya)開關接觸電(dian)(dian)阻(zu)阻(zu)值。

（4） LCD 顯(xian)示結果：主要(yao)調用(yong)顯(xian)示子程序(xu)將檢測到的電流(liu)值繪制成曲線以及顯(xian)示接觸電阻阻值。

3 高壓開關接(jie)觸電阻測試儀的技術性能指標

供(gong)電電壓：AC220V；

測試對象：高壓開關、接觸器等開關器件的接觸電阻；

測量范(fan)圍：1～5000μΩ；

測試電流（峰(feng)值(zhi)）：100～500A；

分辨率：1μΩ；

準(zhun)確度：0．2％。

4 結語

本文采(cai)用(yong)脈沖電源?結(jie)合嵌(qian)入式(shi)系統(tong)在數據采(cai)集和(he)數據處理中的速度(du)優勢?設計出一種在**度(du)和(he)穩定度(du)都滿足要(yao)求的前提下?便于攜帶和(he)現場使(shi)用(yong)的高壓(ya)開關接觸電阻測(ce)試(shi)儀。實際應(ying)用(yong)表(biao)明?該測(ce)試(shi)儀在測(ce)量(liang)(liang)精度(du)和(he)穩定性上比采(cai)用(yong)傳(chuan)統(tong)測(ce)量(liang)(liang)方法有(you)(you)了(le)較大的提高?且體積小、重(zhong)量(liang)(liang)輕?給(gei)現場測(ce)試(shi)帶來了(le)方便?有(you)(you)較好的應(ying)用(yong)推廣價值(zhi)。