A . A、先合KJDK接地刀开关和DCK蓄电池刀开关，再合KGK整流器刀开关
B . B、先合KJDK接地刀开关KGK整流器刀开关，再合DCK蓄电池刀开关
C . C、先合DCK蓄电池刀开关KGK整流器刀开关，再合KJDK接地刀开关
D . D、须同时合上三个开关