三相電加熱管

        380伏三相(xiang)(xiang)四線(xian)電(dian)(dian)(dian)路中，任(ren)意兩(liang)根火(huo)線(xian)之間的電(dian)(dian)(dian)壓都(dou)(dou)是380伏，任(ren)意一根火(huo)線(xian)與零線(xian)之間都(dou)(dou)可以組成(cheng)220伏。這個(ge)系(xi)統可以形成(cheng)三種(zhong)(zhong)電(dian)(dian)(dian)源：即(ji)單(dan)(dan)相(xiang)(xiang)220伏電(dian)(dian)(dian)源，單(dan)(dan)相(xiang)(xiang)380伏電(dian)(dian)(dian)源，三相(xiang)(xiang)380伏電(dian)(dian)(dian)源，第 I 種(zhong)(zhong)家用比較(jiao)多，第三種(zhong)(zhong)工(gong)廠里電(dian)(dian)(dian)機類用得多，第二種(zhong)(zhong)用得少，只(zhi)有交(jiao)流電(dian)(dian)(dian)焊(han)機經常(chang)用到單(dan)(dan)相(xiang)(xiang)380伏電(dian)(dian)(dian)源。