Eaton Power Xpert 9395P-1100/1100 Installation And Operation Manual

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130 Eaton® Power Xpert® 9395P-1200 Installation and Operation Manual 164000500—Rev 11The distributed bypass system can be transferred from Online 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 Online mode due to an outputvoltage deviation, the distributed bypass system automatically attempts to return to Online mode (up to threetimes within a 10–minute period). After three transfer attempts or an overload, the system locks the criticalload to 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 Online 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 75 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 visual indicator lamps 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 inthis operating mode until the input power to the rectifier is again within the specified voltage or frequencyacceptance windows.If the input power fails to return or is not within the acceptance windows required for normal operation, thebattery continues discharging until a DC voltage level is reached where the inverter output can no longersupport the shared loads. When this event occurs, each UPS issues another set of audible and visual alarmsthat indicate a two-minute SHUTDOWN IMMINENT warning. Unless the system has a valid AC input soon,redundant UPMs begin shutting down until there are no longer enough UPMs online to support the connectedload. When this event occurs, the system shuts down. If the bypass source is available, the system transfers tobypass instead of shutting down.Understanding UPS Operation