Vertiv Liebert APS series, Installer And User Manual

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2.5 Operating Modes
The Liebert APS is a true online double-conversion system, with the following operating modes:
• Normal Mode
• Backup Mode
• Auto Restart Mode
• Bypass Mode
2.5.1 Normal Mode
The power-module rectifiers derive power from a utility AC source and supply regulated DC power to the
inverter. The module’s inverter regenerates precise AC power to supply the connected equipment. The
battery charger is in the power module and maintains a float-charge on the batteries of the UPS. The
optional charger module can also charge the batteries to maintain a quicker recharge time for long back-
up time applications.
2.5.2 Backup Mode
When AC utility fails, the connected equipment is supplied power by the inverter, which obtains energy
from the battery modules. The output power will not be interrupted during the failure or restoration of the
AC utility/mains source.
2.5.3 Auto Restart Mode
After a power outage and complete battery discharge, and once AC utility is restored, the UPS
automatically restarts and resumes supplying power to connected equipment. This feature is enabled at
the factory, but can be disabled by you. You can also program two auto-restart delay settings from the
LCD:
• Battery capacity level (%)
• Countdown timer
2.5.4 Bypass Mode
The bypass provides an alternate path for power to the connected equipment and operates as follows:
• Automatic: In the event of an internal fault or the inverter overload capacity be exceeded, the
UPS performs an automatic transfer of the connected equipment from the inverter to the
bypass source.
• Manual: If the UPS needs taken out of service for limited maintenance or repair, manual
activation of the bypass causes an immediate transfer of the equipment from the inverter to
the bypass source.
Vertiv | Liebert® APS™ Installer/User Guide | 22