Filter
Top Products
Understanding UPS Operation
7-11
EATON Powerware
®
9390 UPS (100–160 kVA) Installation and Operation Manual S 164201604 Rev B powerware.com
7.3.2 Normal Mode – Parallel
In Normal mode, utility AC power is supplied to the UPMs. Each UPM then conditions the
incoming AC power and provides clean, regulated AC power to either a module tie cabinet
or distribution panel for parallel systems up tofourmodules.Theappliedloadisequally
shared among the available UPMs in the system.
Figure 7-5 shows the path of electrical power through the parallel system when operating
in Normal 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 7-5. Path of Current through the UPMs in Normal Mode – Parallel
If the utility AC power is interrupted or is out of specification, the UPMs automatically
switch to Battery mode to support the critical load without interruption. When utility
power returns, the UPMs return to Normal mode.
IftheUPMsbecomeoverloadedorunavailable,theparallelsystemswitchestoBypass
mode. The parallel system automatically returns to Normal mode when the overload
condition is cleared and system operation is restored within specified limits.