Powerware 9390 UPS 100160 kVA - Manual (Page 60)

UNDERSTANDING UPS OPERATION
EATON Powerware ® 9390 UPS (20–80 kVA) Installation and Operation Manual S 164201603 Rev 2 www.powerware.com 7-8
7.2.1 Multiple Module Parallel System Modes
Similar to the single module system, the Powerware 9390 UPS parallel system
supports a critical load in three different modes of operation. The standard operation
modes are:
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In Normal mode, the paralleled UPMs supply the critical load with clean, filtered
power. Each UPM battery charger also provides charging current for the battery if
needed.
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In Battery mode, the battery provides DC power, which maintains UPM operation.
The UPM batteries support the critical load.
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In Bypass mode, the critical load is directly supported by utility power through the
continuous-duty static bypass switch in each UPM.
The UPMs continually monitor themselves and the incoming utility power, and
automatically switch between these modes as required, without operator
intervention, except when manually switching to Bypass mode. The sophisticated
detection and switching logic inside the UPMs ensures that operating mode changes
are automatic and transparent to the critical load, while internal monitoring systems
indicate the current mode of operation. The UPMs switch operating modes in
response to these system events:
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A command is an intervention that is externally initiated by an operator or by some
site action. A command causes the UPMs to switch operating modes; it usually
does not require any further action.
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A notice is a minor system event that may or may not require attention.
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An alarm is a system event that requires immediate intervention.
System events, alarm horns, and indicator lights are described in Chapter 11,
“Responding to System Events.”
To assist in developing an understanding of the parallel system modes of operation,
review and understand thoroughly the single module modes of operation.
The following paragraphs describe the differences in the three parallel system
operating modes, using block diagrams to show the power flow during each mode of
operation.