ZX7-200焊機外殼實際上就是(shi)(shi)(shi)具有下降(jiang)外(wai)(wai)特(te)(te)性(xing)的變(bian)(bian)壓(ya)器，將220V和(he)(he)380V交流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)變(bian)(bian)為低(di)壓(ya)的直(zhi)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)焊(han)機(ji)一般按(an)輸(shu)出電(dian)(dian)(dian)(dian)源種類可(ke)分為兩種，一種是(shi)(shi)(shi)交流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)源的；一種是(shi)(shi)(shi)直(zhi)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)的。直(zhi)流(liu)(liu)(liu)的電(dian)(dian)(dian)(dian)焊(han)機(ji)可(ke)以(yi)說也是(shi)(shi)(shi)一個大功率的整流(liu)(liu)(liu)器，分正負，交流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)輸(shu)入時(shi)，經(jing)變(bian)(bian)壓(ya)器變(bian)(bian)壓(ya)后，再由整流(liu)(liu)(liu)器整流(liu)(liu)(liu)，然后輸(shu)出具有下降(jiang)外(wai)(wai)特(te)(te)性(xing)的電(dian)(dian)(dian)(dian)源，輸(shu)出端(duan)在(zai)接(jie)通和(he)(he)斷開時(shi)會產(chan)生巨(ju)大的電(dian)(dian)(dian)(dian)壓(ya)變(bian)(bian)化(hua)，兩在(zai)瞬間短路時(shi)引燃(ran)電(dian)(dian)(dian)(dian)弧，利用(yong)產(chan)生的電(dian)(dian)(dian)(dian)弧來(lai)熔(rong)化(hua)電(dian)(dian)(dian)(dian)焊(han)條和(he)(he)焊(han)材(cai)，冷卻后來(lai)達到使它們結合的目的。焊(han)接(jie)變(bian)(bian)壓(ya)器有自(zi)身(shen)的特(te)(te)點，外(wai)(wai)特(te)(te)性(xing)就是(shi)(shi)(shi)在(zai)焊(han)條引燃(ran)后電(dian)(dian)(dian)(dian)壓(ya)急劇下降(jiang)的特(te)(te)性(xing)。

ZX7-200焊機外殼的(de)主要部(bu)件(jian)是一個(ge)降壓(ya)變壓(ya)器，次(ci)級線圈(quan)的(de)兩端是被焊(han)(han)接工(gong)件(jian)和焊(han)(han)條(tiao)，工(gong)作時引燃電弧，在電弧的(de)高(gao)溫(wen)中將焊(han)(han)條(tiao)熔(rong)接于工(gong)件(jian)的(de)縫隙中。由于電焊(han)(han)變壓(ya)器的(de)鐵芯有自身的(de)特點，因此具有電壓(ya)急(ji)劇下降的(de)特性，即在焊(han)(han)條(tiao)引燃后電壓(ya)下降；在焊(han)(han)條(tiao)被粘連短(duan)路 時，電壓(ya)   是急(ji)劇下降。

在(zai)焊(han)(han)(han)接(jie)(jie)操作時，雖然電(dian)(dian)(dian)(dian)路中的(de)電(dian)(dian)(dian)(dian)流處處相等，但由(you)于各(ge)處的(de)電(dian)(dian)(dian)(dian)阻(zu)(zu) 不一(yi)樣，在(zai)不固定接(jie)(jie)觸處的(de)電(dian)(dian)(dian)(dian)阻(zu)(zu)    大(這(zhe)個電(dian)(dian)(dian)(dian)阻(zu)(zu)叫接(jie)(jie)觸電(dian)(dian)(dian)(dian)阻(zu)(zu))，根據電(dian)(dian)(dian)(dian) 流的(de)熱(re)效(xiao)應定律(lv)(也(ye)叫焦爾定律(lv))，即 Q=IR．t可知：在(zai)電(dian)(dian)(dian)(dian)流相等時，則電(dian)(dian)(dian)(dian) 阻(zu)(zu)越大的(de)部(bu)位(wei)發熱(re)越高，因(yin)此在(zai)焊(han)(han)(han) 接(jie)(jie)時，焊(han)(han)(han)條(tiao)(tiao)的(de)觸頭也(ye)就(jiu)是被(bei)接(jie)(jie)的(de)金(jin) 屬體(ti)的(de)接(jie)(jie)觸處的(de)接(jie)(jie)觸電(dian)(dian)(dian)(dian)阻(zu)(zu)   大，則 在(zai)這(zhe)個部(bu)位(wei)產生的(de)電(dian)(dian)(dian)(dian)熱(re)自然也(ye)就(jiu)    多，加之(zhi)焊(han)(han)(han)條(tiao)(tiao)是熔(rong)點較(jiao)低的(de)合金(jin)，自然容(rong)易(yi)熔(rong)化(hua)。熔(rong)化(hua)后(hou)的(de)合金(jin)焊(han)(han)(han)條(tiao)(tiao)芯 粘(zhan)合在(zai)被(bei)焊(han)(han)(han)物體(ti)上(shang)，冷卻(que)后(hou)便(bian)把焊(han)(han)(han) 接(jie)(jie)對象粘(zhan)合在(zai)一(yi)塊。

焊機外殼使用(yong)電能(neng)源(yuan)，將電能(neng)瞬間(jian)轉換為熱能(neng)，電很普(pu)遍，ZX7-200焊(han)機(ji)外(wai)殼電焊(han)機(ji)適合在干燥的(de)(de)環境下工作，不需要太多要求，因體積小巧(qiao)，操(cao)作簡單，使用(yong)方便，速度(du)較快，焊(han)接(jie)后焊(han)縫結(jie)實等優(you)點廣(guang)泛用(yong)于各個，特(te)別對要求強(qiang)度(du)很高的(de)(de)制件特(te)實用(yong)，可以瞬間(jian)將同(tong)種金(jin)屬材料（也可將異種金(jin)屬連接(jie)，只是焊(han)接(jie)方法不同(tong)）   性的(de)(de)連接(jie)，焊(han)縫經熱處理后，與母材同(tong)等強(qiang)度(du)，密封(feng)很好，這給儲存氣體和(he)液體容器的(de)(de)制造解(jie)決(jue)了密封(feng)和(he)強(qiang)度(du)的(de)(de)問題。