Eaton 9390IT Installation And Operation Manual

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UNDERSTANDING UPS OPERATIONEaton®9390 UPS (20–80 kVA) and 9390IT (20-40 kVA) Installation and Operation Manual 164201603 Rev 4 www.eaton.com/powerquality7-8If at any time during the battery discharge the input power becomes available again,contactors K1 and K5 close and the rectifier begins to supply DC current to theconverter and inverter. At this point, the unit returns to Normal mode. Depending onthe total load and the duration of the battery discharge, battery current limit alarmsmay be seen for a short time due to the current required to recharge the battery.The system's total operating time on battery depends on many factors. Some factorsthat affect battery support times are battery type and capacity, number of parallelstrings, environmental temperatures, age of the battery, and fluctuations in loaddemand during the discharge. The greater the load, the less support time the batteryhas. Decreasing the load generally increases the battery support time.7.2 Multiple Module Parallel SystemParallel operation extends the normal operation of Eaton 9390 UPS units by offeringincreased capacity and/or redundant capability. The parallel system continues tomaintain power to the critical loads during commercial electrical power brownout,blackout, overvoltage, undervoltage, and out‐of‐tolerance frequency conditions. SeeDrawing 164201603-5, sheets 4 of 6, 5 of 6, and 6 of 6 in Appendix A, for a detailedrelationship of the parallel system.The output of the system is normally supplied by several uninterruptible powermodules (UPMs). Multiple UPMs are connected with their outputs in parallel (tiedtogether) to provide a load level greater than the rating of one UPM and/or forredundancy. The paralleled UPMs supply the output load with protected power aslong as the load does not exceed the combined rating of the paralleled UPMs.The power system is redundant as long as one of the UPMs can be disconnectedfrom the output bus and the remaining UPMs can continue to supply power to theload without exceeding their ratings.When the load is being supplied by the UPMs, the system output bus is continuouslymonitored for an overvoltage or undervoltage condition. If an out of limits condition isdetected, the paralleled UPMs transfer the load to bypass using the UPM staticswitches.Communication is required between the UPMs for system metering and modecontrol. System level communication and control are accomplished using aPowerware Hot Sync CAN Bridge Card. A single building alarm in each UPM,connected to the other UPMs in parallel, and tied to the bypass contactor auxiliarycontacts in each UPM are used for a secondary communication path. Thisarrangement ensures bypass control even if the CAN bus is lost.Up to four units can be paralleled for redundancy or capacity without any additionalcabinets.The system is paralleled for redundancy (1+1) in a system where two UPMs areparalleled together and the load is less than the supporting capability of one of theUPMs. The system is paralleled for capacity (2+0) if both UPMs in a system arerequired to support the load.A parallel capacity system can also be redundant (2+1), as long as there is always oneor more UPMs online than required to support the load.