Eaton 9E - Figure 5-2. Path of Current through the UPS in Standard Normal Mode

Understanding UPS Operation
Eaton 9E UPS (40–60 kVA, 208/220V) Installation and Operation Manual P-164000058—Rev 4 www.eaton.com/powerquality 5-3
If the utility AC power is interrupted or is out of specification, the UPS automatically switches to Battery mode
to support the critical load without interruption. When utility power returns, the UPS returns to Normal mode.
Figure 5-2. Path of Current Through the UPS in standard Normal Mode
If the UPS becomes overloaded or unavailable, the UPS switches to Bypass mode. The UPS automatically
returns to Normal mode when the overload condition is cleared and system operation is restored within
specified limits.
If the UPS suffers an internal failure, it switches automatically to Bypass mode and remains in that mode until
the failure is corrected and the UPS is back in service.
Rectifier Inverter
Battery
Converter
Battery
Relay
Main Power Flow
Output
Output
Relay
Bypass Input
Input
Relay
Input
Breaker
Rectifier
Input
Relays
Breakers
Closed
Open
Battery
Trickle Current
De-Energized
Energized
Static
Switch
Backfeed
Protection Relay