那么一(yi)旦高(gao)于變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)額定(ding)(ding)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)時(shi)會有什(shen)么危(wei)害呢？通(tong)常，變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)在額定(ding)(ding)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)下運行時(shi)，鐵芯中(zhong)的(de)(de)(de)磁(ci)通(tong)密(mi)度已接近飽和狀態(tai)。如果電(dian)(dian)(dian)源電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)高(gao)于額定(ding)(ding)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)，則勵磁(ci)電(dian)(dian)(dian)流將急(ji)劇增大，功率因(yin)數隨之降低(di)。此(ci)外，電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)過高(gao)還可能燒(shao)(shao)壞變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)的(de)(de)(de)繞(rao)組。當(dang)電(dian)(dian)(dian)源電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)超過額定(ding)(ding)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)的(de)(de)(de)105時(shi)，變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)繞(rao)組電(dian)(dian)(dian)勢的(de)(de)(de)波形(xing)就(jiu)會發生較大的(de)(de)(de)畸變(bian)(bian)，其(qi)中(zhong)含有較多的(de)(de)(de)高(gao)次諧波分(fen)量(liang)，會使電(dian)(dian)(dian)勢最(zui)大值增高(gao)，從而(er)損壞繞(rao)組絕(jue)緣。 另一(yi)方面(mian)，電(dian)(dian)(dian)源電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)過高(gao)，變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)的(de)(de)(de)輸出電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)也會相應增大，這不(bu)(bu)但會導致(zhi)用電(dian)(dian)(dian)設(she)備過負(fu)荷(he)、過電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)，而(er)且還將降低(di)用電(dian)(dian)(dian)設(she)備的(de)(de)(de)壽命(ming)，嚴重時(shi)甚至擊穿絕(jue)緣，燒(shao)(shao)壞設(she)備。 因(yin)此(ci)，為了保(bao)證變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)和用電(dian)(dian)(dian)設(she)備安全運行，規(gui)定(ding)(ding)變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)的(de)(de)(de)輸入電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)，即電(dian)(dian)(dian)源電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)不(bu)(bu)得大于變(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)額定(ding)(ding)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)的(de)(de)(de)105。