380伏(fu)三(san)(san)相(xiang)四(si)線(xian)電(dian)(dian)路中,任(ren)意兩根火(huo)線(xian)之間的電(dian)(dian)壓都(dou)是380伏(fu),任(ren)意一根火(huo)線(xian)與零線(xian)之間都(dou)可以組成(cheng)220伏(fu)。這(zhe)個系統可以形(xing)成(cheng)三(san)(san)種(zhong)(zhong)電(dian)(dian)源(yuan):即單(dan)相(xiang)220伏(fu)電(dian)(dian)源(yuan),單(dan)相(xiang)380伏(fu)電(dian)(dian)源(yuan),三(san)(san)相(xiang)380伏(fu)電(dian)(dian)源(yuan),第 I 種(zhong)(zhong)家用(yong)比較多,第三(san)(san)種(zhong)(zhong)工廠里電(dian)(dian)機(ji)類用(yong)得多,第二種(zhong)(zhong)用(yong)得少,只有交(jiao)流(liu)電(dian)(dian)焊機(ji)經常(chang)用(yong)到單(dan)相(xiang)380伏(fu)電(dian)(dian)源(yuan)。