380伏(fu)(fu)(fu)三相四線(xian)電(dian)路中,任意兩(liang)根火線(xian)之(zhi)間的電(dian)壓都是380伏(fu)(fu)(fu),任意一根火線(xian)與零線(xian)之(zhi)間都可(ke)以組(zu)成220伏(fu)(fu)(fu)。這個系統可(ke)以形(xing)成三種電(dian)源(yuan):即單相220伏(fu)(fu)(fu)電(dian)源(yuan),單相380伏(fu)(fu)(fu)電(dian)源(yuan),三相380伏(fu)(fu)(fu)電(dian)源(yuan),第(di)(di) I 種家用(yong)比較多,第(di)(di)三種工廠里電(dian)機(ji)類用(yong)得(de)多,第(di)(di)二種用(yong)得(de)少,只(zhi)有(you)交流(liu)電(dian)焊機(ji)經常用(yong)到單相380伏(fu)(fu)(fu)電(dian)源(yuan)。