Liebert 1000kVA manual Load on Bypass, OK to Transfer

Operation

3.3.1Load on Bypass

Load on Bypass, with the UPS not available, is shown in Figure 52. The UPS system could be in this mode of operation during either initial start-up or UPS system shutdown and isolation for mainte- nance.

NOTE

When the critical load is being supplied power from the bypass line, it is exposed to utility power disturbances.

Figure 52 Load on bypass, UPS not available

		RIB			RIB			RIB		BFB
UPS #3			UPS #2			UPS		#1
CB1			CB1			CB1
								SBS
										BIB
	R			R			R		SBB
	I			I			I				MBB
								System
CB2			CB2			CB2				SKRU
								Controls

Output

MIB

					SCCT
					To Critical Load
	MBD		MBD		MBD
					SCCT
Battery		Battery		Battery
					(can accommodate up to 6 UPS modules)

3.3.2OK to Transfer

The OK to Transfer status message will be displayed when the bypass line and UPS system output power are both available, their voltage, frequency and phase synchronization are matched within specifications and the Static Switch Disconnects are closed (ON). An alarm message may be displayed to indicate Load On Bypass. If no alarm is displayed, the operating status is Load On UPS.

When the OK to Transfer message is displayed, you can perform a manual transfer of the load from the UPS system to bypass or a manual retransfer of the load from bypass to the UPS system.

Use the Load Transfer Procedures screen at the SCC when performing a manual transfer. Refer to 3.4.3 - Load Transfer Procedures.

The UPS system control logic at the SCC will initiate an automatic transfer to bypass if an overload condition exceeds the system current versus time window or if a UPS module is taken off line while the system is operating in the non-redundant mode. An automatic retransfer to the UPS system may be initiated when recovering from system overloads lasting less than five minutes. Refer to 3.5 - Automatic Operations.

NOTE

When the critical load is being supplied power from the bypass line, it is exposed to utility power disturbances.

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