88 Eaton 93PM UPS (400V/480V Four-Wire – 100 kW Frame) Installation and Operation Manual 164000566—Rev 0455..22 SSiinnggllee UUPPSSA single UPS operates independently to support an applied load from the inverter, providing conditioned anduninterruptible AC power to the critical load from the output of the module. During an outage, the invertercontinues to operate, supporting power to the load from the battery supply. If the unit requires service, appliedloads are transferred to the internal bypass either automatically or manually. With the exception of an optionalexternal battery cabinet, no other cabinets or equipment are required for the single UPS to successfully supportits applied loads.55..22..11 MMooddeessThe 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 throughthe internal bypass and transfers automatically to Normal mode (double-conversion on demand) if anabnormal condition is detected. The battery charger also provides charging current for the battery, ifneeded.• In Normal (double-conversion) mode, the critical load is supplied by the inverter, which derives its powerfrom rectified utility AC power. In this mode, the battery charger also provides charging current for thebattery, if needed.• In Bypass mode, the critical load is directly supported by utility power. The battery charger also providescharging current for the battery, if needed.• In Battery mode, the battery provides DC power, which maintains inverter operation. The battery supportsthe critical load.The following paragraphs describe the differences in the UPS operating modes, using block diagrams to showthe power flow during each mode of operation.Understanding UPS Operation
