三相電加熱管

        380伏(fu)(fu)三(san)相(xiang)四線(xian)(xian)電(dian)(dian)路中，任意兩(liang)根火(huo)線(xian)(xian)之間的電(dian)(dian)壓都是380伏(fu)(fu)，任意一根火(huo)線(xian)(xian)與零線(xian)(xian)之間都可以(yi)組成220伏(fu)(fu)。這個(ge)系統可以(yi)形成三(san)種(zhong)(zhong)電(dian)(dian)源(yuan)：即單相(xiang)220伏(fu)(fu)電(dian)(dian)源(yuan)，單相(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan)，三(san)相(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan)，第(di) I 種(zhong)(zhong)家用(yong)(yong)比較多(duo)，第(di)三(san)種(zhong)(zhong)工廠里電(dian)(dian)機類用(yong)(yong)得多(duo)，第(di)二(er)種(zhong)(zhong)用(yong)(yong)得少，只有交流電(dian)(dian)焊機經常(chang)用(yong)(yong)到單相(xiang)380伏(fu)(fu)電(dian)(dian)源(yuan)。