UNDERSTANDING UPS OPERATION
Power Xpert
9395 UPS (450–550 kVA) Installation and Operation Manual
164201701 Rev 3
www.eaton.com/powerquality
6-4
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, the bypass source supplies the commercial
AC power to the load directly through the static switch. Some power line filtering and
spike protection is provided to the load but no active power conditioning or battery
support is available. All power converters are off and are in the ready state (in case a
forward transfer is needed). During this mode, the output contactor is closed and the
link is maintained through the diode bridge. Figure 6‐3 shows the path of electrical
power through the UPS system when operating in Energy Saver mode.
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
Static
Switch
Rectifier
Inverter
K1
K3
Battery
Converter
Battery
Battery
Breaker
Main Power Flow
Trickle Current
Energized
De-Energized
Closed
Open
Breakers
Contactors
Input
Breaker
(CB1
Figure 6‐3. Path of Current Through the UPS in Energy Saver Mode
If the bypass source falls outside of a predetermined voltage or frequency window,
the system forward transfers to Battery mode and then to Online mode with the
inverter assuming the load. The transfer takes place with a 2 ms typical transfer time,
to ensure loads being fed by the system output are not interrupted. All forward
transfers transfer to Battery mode before returning to Online mode.
Energy Saver mode is a normal operating mode, and not an alarm condition. While the
UPS is in this mode, the
ONLINE
light on the front display will illuminate.
