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Operation
72
8.0 OPERATION
The Liebert APM operates in the modes shown in Table 22. This section describes various kinds of
operating procedures under each operating mode, including transfer between operating modes, UPS
setting and procedures for turning on/off inverter.
As shown in Figure 48, the AC utility source is supplied through the input breaker, and the rectifier
converts the alternating current into DC power. The inverter converts the AC power from the
utility—or DC power from the batteries—into AC power for the load. The batteries power the load
through the inverter in the event of a power failure. The utility source can also power the load
through the static bypass.
If maintenance or repair of the UPS is necessary, the load can be switched without interruption in
service using the Liebert BDC.
Figure 48 Single module block diagram—Single input configuration with three-breaker Liebert BDC
!
WARNING
Risk of electrical shock and arc flash. Can cause property damage, injury and death.
The Liebert
®
APM
™
contains high voltages internally. Components that can only be accessed
by opening the protective cover with tools cannot be serviced or replaced by the user.
Only properly trained and qualified service personnel are authorized to remove the protective
covers.
Table 22 UPS operating modes
Operating mode Descriptions
Normal mode NORMAL UPS powers the load
Bypass mode BYPASS
The load power supply is provided by the static bypass. This mode can be regarded
as a temporary transition mode between the normal mode and maintenance bypass
mode, or a temporary abnormal operating status.
Maintenance
Mode
MAINT
UPS shuts down, the load is connects to the mains through the Liebert BDC. In this
mode the load is not protected against abnormal input utility power.