DC NORMAL GENERATION SWITCHINGThis circuit monitors and controls the DC normal network supply (DCBUS 1, DC BUS 2 and DC BAT BUS).The switching enables:- normal supply of the DC busbars,- automatic power transfer in case of failure and,- transfer inhibition in case of a short circuit.DC NORMAL BUS SWITCHINGThe switching circuit consists of contactors 1PC1 and 1PC2. Theyare controlled in parallel by the Electronic Contactor ManagementUnits 1 and 2 (ECMU 1 and 2).ECMUThe DC supply configuration is sensed by the ECMUs. Due to supplychanges, the ECMUs provide control logic for contactors 1PC1 and1PC2.In normal supply configuration, contactor 1PC1 is closed and 1PC2is opened.NORMAL OPERATIONIn normal configuration the LH side AC BUS is supplied and TR1 isoperating (contactor 5PU1 closed), ECMU1 internal control logiccloses contactor 1PC1. 1PC1 contactor control logics only active inECMU 1 and ECMU 2 internal control logic keeps contactor 1PC2open.ABNORMAL OPERATIONIf TR1 fails, not due to over-current, ECMU1 detects that 5PU1 isopen, and then opens 1PC1.ECMU2 detects that 1PC1 is open and closes 1PC2 to supply DCBAT BUS.As soon as 1PC2 is closed, ECMU2 closes 1PC1 to supply DC BUS1 from DC BAT BUS.TR2 now supplies the three DC buses (DC BUS 2, DC BAT BUS andDC BUS1).If TR1 fails due to over-current, contactor 5PU1 opens. ECMU1 opens1PC1.The TR1 overcurrent signal inhibits the closure of 1PC2 and 1PC1.If TR1 and TR2 are faulty, contactors 1PC1 and 2, and 5PU1 and 2stay open.Power is no longer supplied on DC BUS 1, DC BUS 2 and DC BATBUS.