74 Eaton 93PM UPS 480V Three-Wire – 100 kW Frame Installation and Operation Manual 164000227—Rev 07
55..22 SSiinnggllee UUPPSS
A single UPS operates independently to support an applied load from the inverter, providing conditioned and
uninterruptible AC power to the critical load from the output of the module. During an outage, the inverter
continues to operate, supporting power to the load from the battery supply. If the unit requires service, applied
loads are transferred to the internal bypass either automatically or manually.
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The Eaton 93PM UPS supports a critical load in four different modes of operation:
• In Energy Saver System (ESS) mode, commercial AC power is supplied directly to the critical load through
the internal bypass and transfers automatically to Normal mode (double-conversion on demand) if an
abnormal condition is detected. The battery charger also provides charging current for the battery, if
needed.
• In Normal (double-conversion) mode, the critical load is supplied by the inverter, which derives its power
from rectified utility AC power. In this mode, the battery charger also provides charging current for the
battery, if needed.
• In Bypass mode, the critical load is directly supported by utility power. The battery charger also provides
charging current for the battery, if needed.
• In Battery mode, the battery provides DC power, which maintains inverter operation. The battery supports
the critical load.
The following paragraphs describe the differences in the UPS operating modes, using block diagrams to show
the power flow during each mode of operation.
Understanding UPS Operation
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