當市電(dian)(dian)供電(dian)(dian)中斷(duan)或(huo)市電(dian)(dian)電(dian)(dian)壓(ya)超限 (±15%或(huo)±20%額定輸(shu)入電(dian)(dian)壓(ya))時(shi)(shi),互投裝置將立(li)即投切(qie)至(zhi)逆變(bian)器(qi)供電(dian)(dian),在(zai)電(dian)(dian)池(chi)組(zu)所提供的(de)直流(liu)能源(yuan)的(de)支持下,此時(shi)(shi),用(yong)(yong)戶負(fu)載所使用(yong)(yong)的(de)電(dian)(dian)源(yuan)是通(tong)過EPS的(de)逆變(bian)器(qi)轉(zhuan)換的(de)交流(liu)電(dian)(dian)源(yuan),而(er)不是來自市電(dian)(dian)