Eaton 9E Installation And Operation Manual

Also see for 9E: Installation and operation manual Installation and operation manual Installation and operation manual Manual Manual

Contents

Understanding UPS Operation5-4 Eaton 9E UPS (20–30 kVA, 208/220V) Installation and Operation Manual 164202124—Rev 2 www.eaton.com/powerquality5.2.4 Bypass ModeCAUTIONThe critical load is not protected from voltage or frequency fluctuations or power outages whilethe UPS is in Bypass mode.The UPS automatically switches to Bypass mode if it detects an overload, load fault, or internal failure. The UPScan also be transferred from Normal mode to Bypass mode manually. The bypass source supplies thecommercial AC power to the load directly. Figure 5-3 shows the path of electrical power through the UPSsystem when operating in Bypass mode.In Bypass mode, the output of the system is provided with three-phase AC power directly from the systeminput. While in this mode, the output of the system is not protected from voltage or frequency fluctuations orpower outages from the source. Some power line filtering and spike protection is provided to the load but noactive power conditioning or battery support is available to the output of the system in the Bypass mode ofoperation.The internal bypass is comprised of a solid-state, silicon-controlled rectifier (SCR) continuous static switch, anda backfeed protection relay. The static switch is used instantaneously anytime the inverter is unable to supportthe applied load. The continuous static switch is wired in series with the backfeed protection relay, and togetherthey are wired in parallel with the rectifier and inverter.The static switch, being an electronically-controlled device, can be turned on immediately to pick up the loadfrom the inverter while inverter output relay opens to isolate the inverter. The backfeed protection relay isnormally closed, ready to support the static switch unless the bypass input source becomes unavailable.If the UPS transfers to Bypass mode from Normal mode due to any reason other than operator intervention,the UPS automatically attempts to transfer back to Normal mode (up to three times within a ten minute period).The fourth transfer locks the critical load to the bypass source and requires operator intervention to transfer.Figure 5-3. Path of Current Through the UPS in Bypass ModeBypass Input StaticSwitchBackfeedProtection RelayRectifier InverterOutputRelayInputRelayInputBreakerRectifierInput OutputBatteryConverterBatteryRelayMain Power FlowRelaysBreakersClosedOpenBatteryTrickle CurrentDe-EnergizedEnergized