Eaton Power Xpert 9395 UPS, Installation And Operation Manual

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Understanding UPS Operation
6-4 Power Xpert
TM
9395 UPS (450–825 kVA) Installation and Operation Manual 164201725—Rev 10 www.eaton.com/powerquality
6.2.3 Energy Saver System Mode
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.
If commercial power voltage or frequency disturbances are detected, the system forward transfers to Battery
mode for minor disturbances and then to double conversion mode for more severe disturbances. During a
complete power outage, the transfer takes place within 2 ms to ensure loads being fed by the system output
are not interrupted. All forward transfers transfer to Battery mode before returning to double conversion mode.
In High Alert mode the unit transfers from ESS mode to double conversion mode or if in double conversion
mode remains in double conversion mode for a default time period of one hour (customer configurable). At the
completion of the time period, the unit defaults back to ESS mode. If the High Alert command is received during
the time period, the timer will be restarted.
ESS 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.
6.2.4 Harmonic Reduction System (HRS)
The Harmonic Reduction system mode of the 9395 UPS allows the UPS to actively reduce the input Total
Demand Distortion (TDD) and increase the input power factor while maintaining high efficiency operation in
ESS mode. The UPS uses one of its UPMs to perform this active harmonic cancellation.
HRS mode uses an extra set of sensors (CTs) on the output bus of the unit. These sensors measure the
harmonics created by loads attached to the UPS output and the system actively reduces these harmonics.
HRS is a normal operating mode, not an alarm condition. The NORMAL light appears on the front of the UPS.
In HRS, the inverter is ON, the rectifier is OFF and the output contactor is CLOSED.
If the bypass source falls outside of a predetermined voltage or frequency level, the system forward transfers
to Battery mode and then to Normal mode with the inverter assuming the load. This transfer takes place within
two milliseconds to ensure loads being fed by the system output are not interrupted. All forward transfers go
to Battery mode before returning to Normal mode.
6.2.5 Variable Module Management System
In VMMS mode, the UPS operates as a traditional double-conversion UPS. However, the UPS will selectively
shift the load to fewer UPMs based on the required load in order to force the remaining UPMs to carry a higher
load. The efficiency rating for each UPM is highest when loads are greater than 50% of the system rating.
Therefore, with multiple UPMs, a UPS can achieve higher efficiencies for lighter loads.
NOTE VMMS and ESS modes are mutually exclusive. If ESS mode is enabled, VMMS
mode is disabled.
NOTE ESS mode requires the UPS to be factory built with a Continuous Static Switch
(CSS).
NOTE Total Demand Distortion as defined by IEEE 519-1992 is the total root-sum-square
harmonic current distortion, in percent, of the maximum demand load current (the
nameplate rating of a fully rated UPS).
NOTE VMMS and ESS modes are mutually exclusive. If VMMS mode is enabled, ESS
mode is disabled.