Liebert NXL UPS
Operation and Maintenance Manual
250-300-400-800kVA
Page 46
2.6 Automatic Operations
The Liebert NXL UPS system is designed to function while unattended by an operator. The
system control logic monitors the performance of the UPS, the availability of power sources
and the current required by the critical load.
The system control logic:
•
Determines what overload conditions can be sustained without a transfer to bypass.
•
Initiates an automatic transfer to bypass to sustain an overload or when selected
UPS faults occur.
•
Can initiate an automatic retransfer to the UPS after an overload has been cleared.
•
Initiates an automatic transfer to bypass and emergency module shutdown when
specified UPS faults occur.
2.6.1
Overloads (Without Transfer)
The UPS system is capable of sustaining full output voltage (±2% of the nominal voltage)
for overload conditions that remain within (under) the current versus time curve of
overload capacity (Figure 37).
Note that the time scale is not linear.
For high current demands of short duration (momentary overloads) the critical load is
supplied simultaneously by both the UPS system and the bypass line. Whenever an
overload condition occurs, you should determine the cause of the overload. If an overload
condition exceeds the overload capacity, the UPS system initiates an automatic load
transfer to the bypass line.
Figure 37
Current-versus-time curves of overload capacity
85 min
60 min
10 min
1 min
1
5
0
%
1
2
5
%
1
1
0
%
1
0
5
%
Summary of Contents for Liebert NXL series
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