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Operation 83
3.2.5 One Module Off-Line
A multi-module UPS system can be supplied with a back-up (redundant) UPS module, which is the typical con-
figuration. A redundant system includes one more module than the number required to supply the critical load. A
redundant system operates in the redundant mode if all modules are ON LINE. Note that the UPS system can
also operate in the redundant mode with one module OFF LINE if the critical load is reduced so that not all ON
LINE modules are required. The UPS modules share the load, and the critical load will remain on the UPS sys-
tem if any one of the modules is disconnected (goes OFF LINE) for maintenance or because of an internal fault.
The system control logic monitors the connected critical load and the number of UPS modules ON LINE. If the
UPS system is operating in the redundant mode, the REDUNDANT status message will be displayed at the Sys-
tem Control Cabinet (SCC). If the UPS system is operating in the non-redundant mode (redundant module is
OFF LINE or was not included in the system configuration), the NON-REDUNDANT status message is dis-
played at the SCC. In the Non-Redundant mode, the critical load will be transferred to bypass if any UPS module
goes OFF LINE, and you must transfer the load to bypass in order to perform maintenance on any UPS module.
Figure 52 One Module Off-Line (Load on UPS)
BIB
SKRU
MIB
MBB
I
R
#2UPS
CB1
CB2
System
Controls
RIB RIB
RIB BFB
Output
SBB
SBS
RIB RIB
RIB BFB
I
R
#1UPS
CB1
CB2
I
R
#3UPS
CB1
CB2
SCCT
SCCT
(can accommodate up to 6 UPS modules)
To CriticalLoad
Battery
MBD
Battery
MBD
Battery
MBD