三相電加熱管

        380伏(fu)三(san)相(xiang)四線電(dian)(dian)(dian)路中，任意(yi)兩根火(huo)線之(zhi)間(jian)的電(dian)(dian)(dian)壓都是380伏(fu)，任意(yi)一根火(huo)線與零(ling)線之(zhi)間(jian)都可(ke)以組成220伏(fu)。這個系統可(ke)以形成三(san)種(zhong)電(dian)(dian)(dian)源：即單相(xiang)220伏(fu)電(dian)(dian)(dian)源，單相(xiang)380伏(fu)電(dian)(dian)(dian)源，三(san)相(xiang)380伏(fu)電(dian)(dian)(dian)源，第 I 種(zhong)家用比較(jiao)多，第三(san)種(zhong)工(gong)廠里電(dian)(dian)(dian)機(ji)類用得多，第二(er)種(zhong)用得少，只有交(jiao)流電(dian)(dian)(dian)焊(han)機(ji)經常用到單相(xiang)380伏(fu)電(dian)(dian)(dian)源。