UNDERSTANDING UPS OPERATION
Eaton 9395 Plus 1 UPS (225–275 kVA) Installation and Operation Manual
S
164201710 Rev 2
www.eaton.com\powerquality
6-3
Static
Switch
Rectifier
Inverter
K1
K3
Battery
Converter
Battery
Battery
Breaker
Main Power Flow
Trickle Current
Energized
De-Energized
Closed
Open
Breakers
Contactors
Static
Switch
K5
Rectifier
Inverter
K1
K3
Main Power Flow
Trickle Current
Energized
De-Energized
Closed
Open
Breakers
Contactors
K2
Bypass Input
Rectifier
Input
Output
Input
Breaker
(CB1
Figure 6‐2. Path of Current Through the UPS in Online Mode
The inverter produces a three-phase AC output to a customer's load without the use
of a transformer. The inverter derives regulated DC from the rectifier and uses IGBT
devices and pulse-width modulation (PWM) to produce a regulated and filtered AC
output. The AC output of the inverter is delivered to the system output through the
output contactor K3.
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 Online mode.
If the UPS becomes overloaded or unavailable, the UPS switches to Bypass mode.
The UPS automatically returns to Online 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.
6.2.3
Energy Saver System Mode
NOTE
VMMS and ESS modes are mutually exclusive. If ESS mode is enabled, VMMS mode is disabled.
When the UPS is operating in ESS mode, commercial AC power is supplied directly to
the critical load through the continuous static switch. Power line filtering and spike
protection for the load are provided by the input and output filter networks, and the
UPS actively monitors the critical bus for power disturbances. When in this mode, the
input and output contactors are closed and the link is maintained through the diode
bridge.