Powerware 9390 UPS 100160 kVA - Manual (Page 64)

UNDERSTANDING UPS OPERATION
EATON Powerware ® 9390 UPS (20–80 kVA) Installation and Operation Manual S 164201603 Rev 2 www.powerware.com 7-12
7.2.4 Battery Mode – Parallel
The UPMs transfer to Battery mode automatically if a utility power outage occurs, or
if the utility power does not conform to specified parameters. In Battery mode, the
battery provides emergency DC power that the inverter converts to AC power.
Figure 7‐7 shows the path of electrical power through the parallel system when
operating in Battery mode.
Main Power Flow
UPM 1
UPM 2
UPM 3
UPM 4
Output to
Critical
Load
Battery
UPM Input
Module Tie Cabinet
UPM 1 Output
Bypass Input
UPM 2 Output
UPM 3 Output
UPM 4 Output
Battery
Battery
Battery
Closed
Open
Breakers
Figure 7‐7. Path of Current through the UPMs in Battery Mode – Parallel
While in Battery mode, the UPMs sound an audible horn, illuminate a visual indicator
lamp on the front panel (System Normal, On Battery), and create an entry into the
alarm event history. As the battery discharges, the boost converter and inverter
constantly make minute adjustments maintaining a steady output. The UPMs remain
in this operating mode until the input power to the rectifier is again within the
specified voltage or frequency acceptance windows.
If the input power fails to return or is not within the acceptance windows required for
normal operation, the battery continues discharging until a DC voltage level is reached
where the inverter output can no longer support the shared loads. When this event
occurs on each UPM, UPMs that are about to be shut down issue another set of
audible and visual alarms that indicate a two-minute SHUTDOWN IMMINENT
warning. Unless the system has a valid AC input soon, redundant UPMs begin
shutting down until there are no longer enough UPMs online to support the
connected load. When this event occurs, the system shuts down. If the bypass
source is available, the system transfers to bypass instead of shutting down.