Emerson 250-400kVA - Manual (Page 26)

Operation
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2.3.2 OK to Transfer
The OK to Transfer status message will be displayed when the bypass line and UPS 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 (Figure 24). If no alarm is displayed, the operating status is Load On UPS
(Figure 25).
When the OK to Transfer message is displayed, the load can be manually transferred from the UPS to
bypass or the load can be manually retransferred from the bypass to the UPS.
To perform a manual transfer, Use the Load Transfer Procedures screen. Refer to 2.4.2 - Load
Transfer Procedures.
The UPS control logic will initiate an automatic transfer to bypass if an overload condition exceeds
the system current versus time window or if a UPS fault is detected. The control logic may initiate an
automatic retransfer to the UPS system when the system is recovering from overloads lasting less
than five minutes. Refer to 2.6 - Automatic Operations.
Figure 24 Load on bypass, UPS available
Figure 25 Load on UPS, bypass available
Bypass
Input
Battery
System
DC Bus
Module
Output
BFB
CB2 CB1
MBD
Bypass
Input
Battery
System
DC Bus
Module
Output
BFB
CB2 CB1
MBD