當市電(dian)(dian)(dian)供電(dian)(dian)(dian)中斷或市電(dian)(dian)(dian)電(dian)(dian)(dian)壓超(chao)限 (±15%或±20%額(e)定輸入電(dian)(dian)(dian)壓)時,互投裝置(zhi)將立即(ji)投切至(zhi)逆(ni)變(bian)器供電(dian)(dian)(dian),在電(dian)(dian)(dian)池組所(suo)提供的直流(liu)能源(yuan)的支持(chi)下,此時,用戶負載(zai)所(suo)使用的電(dian)(dian)(dian)源(yuan)是(shi)通過EPS的逆(ni)變(bian)器轉換的交流(liu)電(dian)(dian)(dian)源(yuan),而不(bu)是(shi)來自(zi)市電(dian)(dian)(dian)