Emerson Liebert NXL series, Operation And Maintenance Manual

Page: 36 / 96

Liebert NXL UPS Operation and Maintenance Manual 250-300-400-800kVA
Page 36
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 29). If no alarm is displayed, the
operating status is Load On UPS (Figure 30).
Figure 29 Load on bypass, UPS available
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 immediately. Refer to 2.6 -
Automatic Operations .
Figure 30 Load on UPS, bypass available
2.3.3 Input Power Failure—Load on Battery
If the utility AC power source fails or is outside the acceptable range, the battery plant
becomes the power source for the UPS module inverters. The UPS continues to supply
power to the critical load and also to the UPS controls.
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Active line