Operation 103
3.4 Automatic Operations
TheLiebert Series 600T UPS system is designed to function while unattendedby an operator. The system con-
trollogic monitors the performance of the UPS, the availabilityof power sources, and the current requiredby the
criticalload.
Thesystem control logic at the SCC
1. Determineswhat overload conditions can be sustained without a transfert o bypass.
2. Initiatesan automatic transfer to bypass to sustain an overload.
3. Caninitiate an automatic retransfer to the UPS after a system overload hasbe encleared.
4. Initiatesan automatic transfer to bypass and emergency module shutdown when a specified UPS fault
occurs.
Thecontrol logic at each UPS module
1. Determineswhat overload conditions can be sustained by them odulewhile it is on-line.
2. Automaticallytakes the UPS module off line and initiatesan emergency module shutdown when selected
UPSfaults occur.

3.4.1 Overloads (Without Transfer)

TheUPS system is capable of sustaining full output voltage(±2% of the nominal voltage) for overload condi-
tionsthat remain within (under) the current versus time curve of system overloadcapacity and the capacity of
moduleson-line (Fi gure 64). Note that the time scaleis not linear. Load On UPS is illustratedin F igure 49.
Forhigh current demands of short duration (momentary overloads) the criticalload is supplied simultaneously
byboth the UPS system and the bypass line. Whenever the critical load requires more than 155% of the capacity
ofthe modules on-line, the bypass line willsupply up to 1000% rated system current throughthe solid state static
switchfor 40 milliseconds. Refer to 3.2.3 - Momentary Overloads.
Wheneveran overload condition occurs, you should determine the cause of the overload.
Ifan overload condition exceeds the UPS system overload capacity or the capacityof the modules on-line, the
UPSsystem initiates an automatic load transfer to the bypass line.
Figure 64 Current-Versus-Time Curves of Module Overload Capacity
DISCONTINUED
PROD U C T