三相電加熱管

        380伏(fu)(fu)三(san)相四線(xian)電(dian)(dian)路中，任意兩(liang)根(gen)火(huo)線(xian)之間的電(dian)(dian)壓(ya)都是380伏(fu)(fu)，任意一根(gen)火(huo)線(xian)與零線(xian)之間都可(ke)以組成220伏(fu)(fu)。這個系統可(ke)以形成三(san)種(zhong)(zhong)電(dian)(dian)源：即單相220伏(fu)(fu)電(dian)(dian)源，單相380伏(fu)(fu)電(dian)(dian)源，三(san)相380伏(fu)(fu)電(dian)(dian)源，第 I 種(zhong)(zhong)家用比較多，第三(san)種(zhong)(zhong)工廠(chang)里電(dian)(dian)機類用得多，第二種(zhong)(zhong)用得少，只有交流電(dian)(dian)焊(han)機經常用到單相380伏(fu)(fu)電(dian)(dian)源。