當市電(dian)(dian)供電(dian)(dian)中(zhong)斷或市電(dian)(dian)電(dian)(dian)壓超(chao)限 (±15%或±20%額定輸入電(dian)(dian)壓)時,互投裝置(zhi)將立即投切至逆變器(qi)供電(dian)(dian),在電(dian)(dian)池組所提供的(de)直流能源的(de)支持下,此時,用戶負載所使用的(de)電(dian)(dian)源是(shi)通過EPS的(de)逆變器(qi)轉換的(de)交(jiao)流電(dian)(dian)源,而不是(shi)來自市電(dian)(dian)