78 Operation
3.2 Modes of Operation
Thissection illustrates the flow of powerthrough circuit breakers, switches, and UPS componentsduring various
modesof operation. An SCCB with three modules is shown. The same modes of operation apply to all configu-
rationsof the Liebert Series 600T UPS multi-module system.Highlighted (thick) lines in the diagramsindicate
powerflow and power availability.
Theseillustrations show a three-breaker maintenance bypassbecause it is most commonly used. Yourinstalla-
tionmay have a two-breaker, three-breaker, or four-breakermaintenance bypass, or none at all.
Theseillustrations do not show an alternate power source (generator)a nd automatictransfer switch (external to
theUPS) that might be present at your installation.
Thefollowing circuit breaker abbreviations are used:

3.2.1 Load On Bypass

Loadon Bypass, with the UPS not available, is shown in Figure 47. The UPS system couldbe in this mode of
operationduring either initial start-up or UPS system shutdown and isolationfor maintenance.
Figure 47 Load on Bypass (UPS Not Available)
BFB Bypass Feeder Breaker
BIB BypassInput Breaker
CB1 Module Input Breaker
CB2 Module Output Breaker
MBB MaintenanceBypass Breaker
MBD ModuleBattery Disconnect
MIB MaintenanceIsolationBreaker
RIB RectifierInput Breaker
SBB System Bypass Breaker
I
R
#2UPS
CB1
CB2
I
R
#1UPS
CB1
System
Controls
I
R
#3UPS
CB1
CB2
RIB RIB
BIB
CB2
SKRU
RIB BFB
MIB
Output
SBB
SBS
MBB
SCCT
(canaccommodate up t o 6UP S modules)
ToCriticalLoad
Battery
MBD
SCCT
Battery
MBD
Battery
MBD
DISCONTINUED
PROD U C T