UNDERSTANDING UPS OPERATIONEATON Power Xpert 9395 UPS (1000–1100 kVA) Installation and Operation Manual 164201764 Rev 3 www.eaton.com/powerquality6-2The emergency bypass consists of either a momentary static switch and wraparoundbypass breaker or a continuous static switch, and a backfeed protection contactor K5.The bypass breaker (if installed) is located in parallel with the static switch. Thebackfeed protection contactor is located in series with the static switch. The staticswitch is armed and ready during normal operation.On a UPS configured as an Input Output Module (IOM), bypass circuitry is notinstalled. This configuration is primarily used in multiple UPS parallel systems that donot need a bypass for each UPS and use a separate System Bypass Module (SBM) toprovide system bypass capabilities.6.2 Single UPSA single UPS operates independently to support an applied load from the inverter,providing conditioned and uninterruptible AC power to the critical load from the outputof the module. During an outage, the inverter continues to operate, supporting powerto the load from the battery supply. If the unit requires service, applied loads aretransferred to the internal bypass either automatically or manually. With the exceptionof a battery cabinet, no other cabinets or equipment are required for the single UPS tosuccessfully support its applied loads.6.2.1 ModesThe Power Xpert 9395 UPS supports a critical load in five different modes ofoperation:NOTE Variable Module Management and Energy Saver modes are mutually exclusive. In Online mode, the critical load is supplied by the inverter, which derives its powerfrom rectified utility AC power. In this mode, the battery charger also providescharging current for the battery, if needed. In Energy Saver mode, commercial AC power is supplied directly to the critical loadthrough the continuous static switch and transfers automatically to Online mode ifan abnormal condition is detected. The Energy Saver mode requires a UPS with acontinuous static switch. In Variable Module Management System mode, the UPS operates as a traditionaldouble-conversion UPS, but selectively shifts the load to fewer UPMs to increasethe efficiency of the UPS. In Bypass mode, the critical load is directly supported by utility power. In Battery mode, the battery provides DC power, which maintains inverteroperation. The battery supports the critical load.The following paragraphs describe the differences in the five UPS operating modes,using block diagrams to show the power flow during each mode of operation.
