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Liebert EXL S1
5. NORMAL AND SAFE OPERATION
5.1. Function
The uninterruptible power supply (UPS) is connected between line power and electrical load. It
protects the load from line power interruptions and power failures.
Warning
To avoid overheating inside the UPS, do not operate the unit for extended periods with the
rectifier running, the Inverter switched off and the Bypass switch open.
5.1.1. On-line Principle
In on-line operation, the alternating voltage of the line power is converted into direct voltage. This DC
voltage is used simultaneously to charge the battery and supply the inverter. The inverter converts
the direct voltage into interference-free alternating voltage at a fixed frequency and amplitude, which
supplies the connected loads. This protects the load from line power disturbances and provides a
secure supply for electrical loads (PCs, network servers, multi-console systems).
In case of a line power failure, the batteries provide uninterrupted power to the loads for a given
period, depending on battery capacity and connected load.
5.1.2. Battery management
The battery is charged and discharged, as well as monitored, using a dedicated microprocessor
control. This ensures maximum battery life. For details, see para 5.2. on page 58.
5.1.3. Bypass-line principal and overload management
In the event of an overload (e.g. > 150% of nominal load), the load is supplied by the inverter for a
limited time (see chap. 9. on page 79, inverter output section) after which, if the Bypass line is available,
the load will be transferred to Bypass; otherwise, the supply to the load will be interrupted. A
corresponding fault message is displayed on the touch screen. To restore the initial conditions, the
output load must first be reduced, and then a manual reset must be carried out to clear the fault
message from the touch screen. Contact customer service for more information. In the event of an
inverter fault, the supply for the load is transferred immediately to the Bypass line. The touch screen
displays the corresponding fault message. Before carrying out a manual reset to restore initial
conditions, it is necessary to remove the root cause of the fault. It is strongly recommended you
contact customer support for more information.
User Manual 10H52264UM60 - Rev. 6 - 12/2021
Figure 25 - UPS in on-line operation
Normal and safe operation
57
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