380伏(fu)(fu)(fu)(fu)三(san)相四線(xian)電(dian)(dian)路中,任(ren)意兩根火線(xian)之間的電(dian)(dian)壓都(dou)(dou)是380伏(fu)(fu)(fu)(fu),任(ren)意一根火線(xian)與(yu)零線(xian)之間都(dou)(dou)可以組成220伏(fu)(fu)(fu)(fu)。這個系(xi)統可以形成三(san)種電(dian)(dian)源(yuan):即(ji)單相220伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan),單相380伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan),三(san)相380伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan),第 I 種家用比較(jiao)多(duo),第三(san)種工廠里電(dian)(dian)機(ji)(ji)類用得多(duo),第二種用得少(shao),只有交流電(dian)(dian)焊機(ji)(ji)經常用到單相380伏(fu)(fu)(fu)(fu)電(dian)(dian)源(yuan)。