Eaton Power Xpert 9395C Installation And Operation Manual

98 Eaton Power Xpert 9395C UPS Installation and Operation Manual 164000821—Rev 06Figure 60. Path of Current through the UPSs in Bypass Mode – Distributed BypassMain Power FlowUPS 1UPS 2Output toCritical LoadBatteryTie CabinetUPS 1 OutputBypass InputUPS 2 OutputBatteryClosedOpenBreakersThe distributed bypass system can be transferred from Normal mode to Bypass mode manually. However, thedistributed bypass system automatically switches to Bypass mode whenever the UPSs can no longer supplythe critical load. If the distributed bypass system transfers to Bypass mode from Normal mode due to an outputvoltage deviation, the distributed bypass system automatically attempts to return to Normal mode (up to threetimes within a 10-minute period). After three transfer attempts or an overload, the system locks the critical loadto the bypass source and requires operator intervention to transfer.Bypass mode is a normal operating mode, not an alarm condition. However, if the distributed bypass system isunable to return to Normal mode following an automatic transfer to Bypass mode, an alarm condition isrecorded.Bypass may also be used when the UPSs or UPMs in the system must be shut down to perform routinemaintenance or repairs.In the Parallel Redundant (N+1) arrangement, the bypass circuitry in each UPS operates to support the appliedloads on bypass. If the UPSs are online and one UPS trips offline, the remaining UPSs do not go to bypass aslong as they have the capacity to support the load.In the Parallel Capacity (N+0) arrangement, if one UPS trips offline and goes to bypass, the remaining UPSsalso go to bypass.66..44..44 BBaatttteerryy MMooddee DDiissttrriibbuutteedd BByyppaassssThe UPSs transfer to Battery mode automatically if a utility power outage occurs, or if the utility power does notconform to specified parameters. In Battery mode, the battery provides emergency DC power that the inverterconverts to AC power.Figure 61 shows the path of electrical power through the distributed bypass system when operating in Batterymode.While in Battery mode, the UPSs sound an audible horn, illuminate a visual indicator lamp on the front panel(Online and On Battery), and create an entry into the alarm event history. As the battery discharges, the boostconverter and inverter constantly make minute adjustments maintaining a steady output. The UPSs remain inUnderstanding UPS Operation