Eaton Powerware 9390 Installation And Operation Manual

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Contents

Understanding UPS Operation7-3EATON Powerware® 9390 UPS (20–80 kVA) Installation and Operation Manual S 164201603 Rev 1 www.powerware.comThe UPS continually monitors itself and the incoming utility power, and automaticallyswitches between these modes as required, without operator intervention. Thesophisticated detection and switching logic inside the UPS ensures that operating modechanges are automatic and transparent to the critical load, while internal monitoringsystems indicate the current mode of operation. The UPS switches operating modes inresponse to these system events: A command is an intervention that is externally initiated by an operator or by some siteaction. A command causes the UPS to switch operating modes; it usually does notrequire any further action. A notice is a minor system event that may or may not require attention. An alarm is a system event that requires immediate operator intervention.System events, alarm horns, and indicator lights are described in Chapter 12, “Respondingto System Events.”The following paragraphs describe the differences in the three UPS operating modes, usingblock diagrams to show the power flow during each mode of operation.