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3.5 Automatic Operations
The Liebert Series 610 UPS system is designed to function while unattended by an operator. The sys-
tem control logic monitors the performance of the UPS, the availability of power sources and the cur-
rent required by the critical load.
The system control logic:
1. Determines what overload conditions can be sustained without a transfer to bypass.
2. Initiates an automatic transfer to bypass to sustain an overload or when selected UPS faults
occur.
3. Can initiate an automatic retransfer to the UPS after an overload has been cleared.
4. Initiates an automatic transfer to bypass and emergency module shutdown when specified UPS
faults occur.
3.5.1 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 58).
Note that the time scale is not linear.
For high current demands of short duration (momentary overloads) the critical load is supplied simul-
taneously by both the UPS system and the bypass line. Refer to 3.3.3 - Momentary Overloads.
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 58 Current-versus-time curves of overload capacity
150%
125%
104%
150%
100%
% Load
1000%
100%
40ms 30s 10m 40ms
PULSED-PARALLEL
(FAULT-CLEARING)
INVERTER OVERLOAD
% Load