Emerson 250-400kVA Automatic Transfers to Bypass, UPS System Faults, Automatic Retransfers to UPS

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Operation

2.6.3Automatic Transfers to Bypass, UPS System Faults

For specified UPS system faults, the control logic will initiate an automatic transfer to bypass fol- lowed immediately by a shutdown and isolation of the UPS system. The output, battery (MBD) and input circuit breakers are open. The bypass breaker will be closed if the bypass line is available. Note that the bypass line is usually not available during Low Battery Shutdown. The circuit diagram is the same as illustrated in Figure 28 for Emergency Module Off.

The following UPS system faults will initiate an automatic transfer to bypass:

DC Overvoltage Shutdown

Hardware Shutdown

Inverter Fault

Low-Battery Shutdown

Output Overvoltage

Overload Shutdown

Overtemperature Timeout

Rectifier Fuse Blown

Reverse Power

Refer to Table 7 for more information about these alarm messages.

NOTE

A load transfer to the bypass line will be completed whenever an automatic transfer to bypass is initiated and the bypass line is available. If the OK to Transfer condition is present, the load transfer will be uninterrupted. If the Static Switch Unable alarm message is present for any reason, the automatic transfer will be interrupted for 40 to 120 milliseconds. Because of the reliability of the UPS components, an interrupted load transfer is a very unlikely occurrence.

Some installations may include a Remote Emergency Power Off mode that can be initiated automati- cally by a contact closure in the critical load equipment. Refer to 2.3.6 - Remote Emergency Power Off.

2.6.4Automatic Retransfers to UPS

In an automatic retransfer, the two circuit breakers (bypass and inverter output) are both closed simultaneously for a short period of time (overlap).

The following critical bus conditions must be present to initiate an automatic retransfer of the critical load from the bypass source to the UPS inverter:

1.Critical load was initially transferred to the bypass source due to a system overload only. A manual retransfer from bypass is required if the transfer to bypass was caused by any condition other than output overload.

2.Overload has since dropped below 100% of the rated load.

3.Both the Input and the Battery (MBD) circuit breakers have remained closed since the overload transfer.

4.OK to Transfer signal received from the control logic for at least 10 seconds, within 5 minutes of the system overload transfer. A manual retransfer from bypass is required for overloads lasting 5 minutes or more.

5.Cyclic-type overloads, which occur up to five (select range is 0 to 5) times in 60 minutes, are automatically returned to the inverter for each event including the Nth overload.

NOTE

If you do not want the UPS system to initiate any automatic retransfers, this can be set during the initial commissioning or by calling your local Liebert Services representative.

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Contents Liebert NXL Battery Cabinet Precautions Contacting Liebert for SupportTable of Contents Specifications Figures Page Important Safety Instructions Normal Mode General DescriptionModes of Operation Bypass Mode Battery ModeMaintenance Bypass OptionsIntroduction Features Main component locationsMimic display Monitor/mimic display example Normal power flow Monitor/mimic display example Utility failMonitor/mimic display example Load on bypass, UPS On Touchscreen Navigation Main Display Screen Menu treeConfigurations Menu Rating Rating ParametersUser Settings System Settings parametersAdjustable Setpoints Adjustable setpoints parametersCell Count Adjustment Event Management Status Reports MenuStartup Menu Shutdown Menu Shutdown menuTransfer/retransfer commands Transfer MenuBattery Management Menu Time remaining displayDisplay summary see Figure Reset MeteringHelp SilenceOK to Transfer Load on bypass, UPS availableInput Power Failure-Load on Battery Input power fail, load on batteryOff Battery Emergency Module OffManual Procedures Remote Emergency Power OffStartup Procedure Startup commands Load Transfer Procedures Transfer ProcedureRe-Transfer Procedure Maintenance Bypass Load TransfersMaintenance Bypass Load Transfers-If Load is on UPS Bypass Shutdown Procedures UPS Shutdown ProcedureSystem Shutdown Procedure Automatic OperationsAutomatic Transfers to Bypass Overload Condition Current-versus-time curves of overload capacityAutomatic Transfers to Bypass, UPS System Faults Automatic Retransfers to UPSSafety Precautions Liebert Services Routine MaintenanceRecord Log Air FiltersBattery Maintenance UPS component service lifeLimited Life Components Component Expected Life ReplaceBattery Safety Precautions Matching Battery Cabinets-Optional Battery voltage, nominal and floatBattery retorque values Torque specifications, unless otherwise labeled Detecting TroubleRack-Mounted Batteries Torque RequirementsReporting a Problem Upstream Feeder Circuit Breaker Setting InspectionsCorrective Actions Battery Operation Environmental specificationsParameter Specification Environmental ConditionsElectrical specifications Battery & DC ParametersLiebert NXL Model Size 250 Input ParametersLiebert NXL Model Size System ParameterPhysical Parameters & Standards, in mm Specifications Liebert NXL alarm and status messages Event Message Event Definition Recommended ActionObserve the One-Line Display. If the input line is Observe the One-Line Display. To identify which Do not Attempt to Close CB3 Until Reset Displayed on the Module Output Meter. If UPS controls monitor the DC Bus positive Resolve the issue that precipitated the EPO Check the One-Line Display for system status UPS, to transfer back to Inverter If this alarm occurs on an operational unit, it Attempt to manually close the disconnect by Module Output Meter. If the load is less than Output Power Factor. If the displayed power factor Until a service visit has been made and action taken When manual transfers are enabled Under normal conditions, no user action is required Observe the One-Line Display and the Active Event If the command to terminate Regeneration Mode If the alarm cannot be reset, or if the alarm condition UPS Alarm and Status Messages UPS Alarm and Status Messages Page Ne t ItiTi n That