47 Eaton® 9390 (100–160 kVA) UPS Installation and Operation Manual 164201604—Rev F
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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
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.
If at any time during the battery discharge the input power becomes available again, the rectifier begins to
supply DC current to the inverter. At this point, the unit returns to Normal mode. If at any time during the
battery discharge the AC input power becomes available again, each rectifier turns on, assumes the inverter
load from the batteries, and begins recharging the batteries. Depending on the total load and the duration of the
battery discharge, battery and rectifier input current limit alarms may be seen for a short time due to the current
required to recharge the batteries.
Understanding UPS Operation
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