當市電(dian)(dian)供(gong)電(dian)(dian)中斷或市電(dian)(dian)電(dian)(dian)壓超限 (±15%或±20%額(e)定輸入(ru)電(dian)(dian)壓)時,互投裝置將立即投切至逆變(bian)器(qi)(qi)供(gong)電(dian)(dian),在(zai)電(dian)(dian)池組所提供(gong)的直流能源的支持下,此時,用戶(hu)負載所使用的電(dian)(dian)源是通過EPS的逆變(bian)器(qi)(qi)轉換(huan)的交流電(dian)(dian)源,而不是來自市電(dian)(dian)