Powerware 9315 - Manual (Page 52)

UNDERSTANDING UPS OPERATION
EATON Powerware ® 9315 UPS (500–750 kVA) Installation and Operation Manual S 164201244 Rev E www.powerware.com 7-2
If utility power is interrupted or falls outside the parameters specified in Chapter 14,
“Product Specifications,” the UPS uses a backup battery supply to maintain power to
the critical load for a specified period of time or until the utility power returns. For
extended power outages, the backup battery supply allows you to either transfer to
an alternative power system (such as a generator) or shut down your critical load in an
orderly manner.
7.1 Operating Modes
The UPS system supports the critical load with the following operating modes:
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Normal mode – The critical load is supplied by the inverter, which derives its power
from rectified utility AC power. In this mode, the rectifier also provides charging
power to the battery.
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Bypass mode – Utility power directly supplies the critical load.
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Battery mode – The battery cabinet provides DC power, which maintains inverter
operation. The battery supports the critical load.
The UPS continually monitors itself and the incoming utility power, and automatically
switches between these modes as required, with no operator intervention. The
sophisticated detection and switching logic inside the UPS ensures that operating
mode changes are automatic and transparent to the critical load. The UPS changes
operating modes in response to:
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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 UPS 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 your attention.
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An alarm is a system event that requires immediate operator intervention.
System events, horns, and indicators are described in Chapter 11, “Responding to
System Events.”
The following paragraphs describe the differences in UPS operating modes, using
block diagrams to show the power flow during each mode of operation.