Eaton 9395 550/275 UPS (225–550 kVA) Installation and Operation Manual 164201716 Rev 2 www.eaton.com/powerquality 6-1Chapter 6 Understanding UPS Operation6.1 UPS System OverviewThe Eaton9395 UPS is a continuous-duty, solid‐state, transformerless (at 480 Vac),three-phase, true online system that provides conditioned and uninterruptible ACpower to the UPS system's output and critical load.The basic system consists of a rectifier, battery converter, inverter,monitoring/operation control panel, integrated communication server, and digitalsignal processor (DSP) logic. Figure 6‐1 shows the main elements of the UPS system.OutputContactorK3BatteryBatteryBreakerBatteryConverterInputContactorK1AC Input toRectifier/ChargerAC Input toBypassBackfeedProtectionContactorK5Power ModuleInverterRectifierDigitalMeteringStaticSwitchAC Outputto CriticalLoadUPS CabinetBatteryContactorK2Battery Cabinet orBattery StringInputBreakerCB1(optional)Figure 6‐1. Main Elements of the UPS SystemIf utility power is interrupted or falls outside the parameters specified in Chapter 10,“Product Specifications,” the UPS uses a backup battery supply to maintain power tothe critical load for a specified period of time or until the utility power returns. Forextended power outages, the UPS allows you to either transfer to an alternativepower system (such as a generator) or shut down your critical load in an orderlymanner.The emergency bypass consists of a continuous-duty static switch and backfeedprotection contactor K5. The backfeed protection contactor is located in series withthe static switch. For manual transfers to bypass, the static switch is also used. Thestatic switch is armed and ready during both types of transfers.Figure
