三相電加熱管

        380伏(fu)(fu)三相(xiang)四線(xian)(xian)電(dian)(dian)路中(zhong)，任(ren)意(yi)兩根火線(xian)(xian)之間的電(dian)(dian)壓都是380伏(fu)(fu)，任(ren)意(yi)一根火線(xian)(xian)與零線(xian)(xian)之間都可(ke)以(yi)組成220伏(fu)(fu)。這個(ge)系(xi)統可(ke)以(yi)形成三種(zhong)電(dian)(dian)源(yuan)(yuan)：即單相(xiang)220伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)，單相(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)，三相(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)，第(di)(di) I 種(zhong)家用(yong)比較多，第(di)(di)三種(zhong)工廠里(li)電(dian)(dian)機(ji)類用(yong)得多，第(di)(di)二種(zhong)用(yong)得少，只有(you)交流電(dian)(dian)焊機(ji)經(jing)常(chang)用(yong)到單相(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan)(yuan)。