Emerson Liebert NXL 250 kVA, Руководство по эксплуатации и обслуживанию

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Operation
53 Liebert
®
NXL
™
2.16.2 Automatic Transfers to Bypass (Overload Condition)
The UPS system will initiate an automatic load transfer to the bypass line if an overload condition
exceeds the current-versus-time curve of overload capacity or if specified UPS system faults occur.
Load On Bypass is illustrated in Figure 30 .
The Overload Transfer and Output Undervoltage alarm messages will initiate an automatic transfer
to bypass and the Load On Bypass message will be displayed. The active event window will display
the Automatic Transfer to Bypass message. Other UPS system faults will initiate an automatic
transfer to bypass followed immediately by the shutdown and isolation of the UPS system. Refer to
2.16.3 - Automatic Transfers to Bypass, UPS System Faults .
In an automatic transfer to bypass the output and bypass circuit breakers do not overlap as they do in
a manual transfer. The static bypass switch is fired (closed), the output circuit breaker is opened, and
the bypass circuit breaker is closed. Bypass power is supplied to the critical load through the static
bypass switch during the short time while both circuit breakers are open.
2.16.3 Automatic Transfers to Bypass, UPS System Faults
For specified UPS system faults, the control logic will initiate an automatic transfer to bypass
followed immediately by a shutdown and isolation of the UPS system. The output, DC source (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 34 for Emergency Module Off.
The following UPS system faults will initiate an automatic transfer to bypass:
• DC Overvoltage Shutdown
• Inverter Fault
• Low-Battery Shutdown
• Output Overvoltage and Undervoltage
• Overload Shutdown
• Equipment Overtemperature
• Rectifier Fuse Blown
Refer to Table 10 for more information about these alarm messages.
Some installations may include a Remote Emergency Power Off mode that can be initiated
automatically by a contact closure in the critical load equipment. Refer to 2.14.6 - Remote
Emergency Power Off .
NOTE
A load transfer to the bypass line will be completed whenever an automatic transfer to bypass
is initiated. 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.
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.