Introduction
Liebert
®
NX
™
4
1.2 Modes of Operation
1.2.1 Normal Mode
Operating in normal mode, the Liebert NX’s rectifier derives power from a utility AC source and
supplies regulated DC power to the inverter, which regenerates precise AC power to supply the
connected equipment. The rectifier also uses the utility source power to charge the DC sources.
1.2.2 Bypass Mode
When the Liebert NX is in bypass mode, the load is directly supported by utility power and is without
DC source backup protection.
The Liebert NX
’
s inverter and bypass static switch will shift the load from the inverter to bypass
mode without an interruption in AC power if the inverter is synchronous with the bypass and any of
the following occurs:
• Inverter fails
• Inverter overload capacity is exceeded
• Inverter is manually turned Off by the user
1.2.3 Battery Mode
When utility AC power fails, the Liebert NX protects the critical load by instantaneously channeling
DC source power to the inverter, which continues supporting the critical load without interruption.
When utility power returns and is within acceptable limits, the Liebert NX automatically shifts back
to Normal mode, with the rectifier powering the critical load.
1.2.4 Maintenance Bypass
The installation of a Maintenance Bypass Cabinet or Assembly is recommended to allow you to totally
isolate the UPS from all power sources. Use of the Maintenance Bypass is described in 2.0 -
Operation.
NOTE
If the inverter is asynchronous with the bypass, the static switch will transfer the load from the
inverter to the bypass WITH interruption in AC power to the critical load. This interruption
will be less than 10ms. This interruption time may be altered by modifying the Output transfer
interrupt time setting.
