Liebert Series 600T 2.0 THEORY OF OPERATION

Theoryof Operation 13

2.0 THEORY OF OPERATION

TheUPS system includes all of the equipment necessary tocontinuously provide computer-grade AC power to a

criticalload, even when there is an interruption ofthe utility line power. It consists ofa System Control Cabinet

(SCC),UPS modules, and a back-up battery plant. Refer to Figure 6 and Figure 7. Except w here otherwise

noted,the configuration is presumed to be parallel-redundant (with at least one more UPS modulethan required

tosupport the rated load).

TheSystem Control Cabinet (SCC) includes system controls,static bypass switch, load transfer control, protec-

tivedevices, and other accessories. The system controls simultaneously monitortwo or more parallel UPS mod-

ulessharing a critical load for increased capacity and/or redundancy.The two (2) motor-operated system circuit

breakers(system bypass breaker—SBB and UPS output breaker) may be contained within theSCC, depending

onthe configuration designed for your installation.

SystemCo ntrols:The system control logic automatically manages criticalbus operation and monitors perfor-

manceof the UPS modules. Microprocessor technology and dedicatedfirmware provide advanced logic control

anda comprehensive display of information. The system controllogic synchronizes the output of the UPS sys-

temto the bypass source. The SCC includes ports for communicating with external devices.Liebert Multi-Mod-

uleUnits do not require an SCC for load sharing. Automatic, parallelmodule load sharing is a function built into

themodules themselves; however interconnection throughthe SCC enables the modules to share data for more

precisecontrol. Modules do not require master clocks or controls in order to loadshare or free-run at 60.0 Hz.

StaticBypass Switch: The static (solid-state) bypassswitch immediately transfers the load from the inverter to

thebypass AC power source in the event of a severe overload on the systemor a failure within the UPS. This

transfertakes place without any interruption of the power suppliedto the load. The system includes redundant

circuits to detect and i solate shorted SCRs in t he static switch.

Fusesare installed in series with the staticbypass circuit to ensure reliable overloadprotection in the unlikely

eventof a catastrophic output condition (e.g., a dropped wrench) electricallyclose to the output of your UPS sys-

tem.The static switch SCRs themselves arerated to easily handle the fuse-blowingcurrent.

Bypass Circuit: The bypass circuit consists of electrically operatedcircuit breakers and associated synchroniz-

ingand control circuitry to transfer the load to/from the bypass source.

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