三相電加熱管

        380伏(fu)(fu)三相(xiang)四線(xian)(xian)電(dian)(dian)路中，任意(yi)兩根火線(xian)(xian)之間的(de)電(dian)(dian)壓都是380伏(fu)(fu)，任意(yi)一根火線(xian)(xian)與零線(xian)(xian)之間都可以組成220伏(fu)(fu)。這(zhe)個系統可以形(xing)成三種(zhong)電(dian)(dian)源：即單(dan)相(xiang)220伏(fu)(fu)電(dian)(dian)源，單(dan)相(xiang)380伏(fu)(fu)電(dian)(dian)源，三相(xiang)380伏(fu)(fu)電(dian)(dian)源，第(di) I 種(zhong)家用比較多(duo)，第(di)三種(zhong)工廠里電(dian)(dian)機(ji)類用得多(duo)，第(di)二種(zhong)用得少(shao)，只有交(jiao)流電(dian)(dian)焊機(ji)經(jing)常(chang)用到單(dan)相(xiang)380伏(fu)(fu)電(dian)(dian)源。