三相電加熱管

        380伏(fu)(fu)(fu)三相(xiang)四線(xian)電(dian)路中，任意兩根火(huo)線(xian)之間的電(dian)壓都是380伏(fu)(fu)(fu)，任意一根火(huo)線(xian)與零線(xian)之間都可以(yi)組成(cheng)220伏(fu)(fu)(fu)。這個系(xi)統可以(yi)形(xing)成(cheng)三種(zhong)電(dian)源(yuan)：即單(dan)相(xiang)220伏(fu)(fu)(fu)電(dian)源(yuan)，單(dan)相(xiang)380伏(fu)(fu)(fu)電(dian)源(yuan)，三相(xiang)380伏(fu)(fu)(fu)電(dian)源(yuan)，第(di) I 種(zhong)家用(yong)(yong)(yong)比(bi)較(jiao)多，第(di)三種(zhong)工(gong)廠里電(dian)機類(lei)用(yong)(yong)(yong)得多，第(di)二種(zhong)用(yong)(yong)(yong)得少(shao)，只有交(jiao)流電(dian)焊機經(jing)常用(yong)(yong)(yong)到單(dan)相(xiang)380伏(fu)(fu)(fu)電(dian)源(yuan)。