當市電(dian)(dian)供(gong)(gong)電(dian)(dian)中(zhong)斷或(huo)市電(dian)(dian)電(dian)(dian)壓超(chao)限 (±15%或(huo)±20%額定(ding)輸入電(dian)(dian)壓)時,互投裝置將(jiang)立即(ji)投切至逆(ni)變器供(gong)(gong)電(dian)(dian),在電(dian)(dian)池組所提供(gong)(gong)的(de)(de)直(zhi)流(liu)能(neng)源的(de)(de)支持下,此時,用(yong)戶負載所使用(yong)的(de)(de)電(dian)(dian)源是(shi)通過EPS的(de)(de)逆(ni)變器轉換的(de)(de)交流(liu)電(dian)(dian)源,而(er)不是(shi)來自市電(dian)(dian)