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5.2Configuring Parallel Sbasystem Operation
5.2.1General
The Liebert® NX™ uses intelligent and reliable decentralized technology to achieve parallel operation of two or more modules.
The parallel system is used to:
•Increase the reliability of the system to ensure adequate power supply to the critical load con- nected.
•Increase serviceability and allow the execution of maintenance operations and repairs without affecting the ordinary operating conditions of the system (depending on the redundancy level).
5.2.2Features of Parallel System
•The controls for parallel UPS module operation are standard in the Liebert NX, and the configu- ration can be set up by changing the settings in configuration software.
•It is easy to install the parallel cables in a ring, providing high reliability and redundancy. And the intelligent paralleling logic provides the user with maximum flexibility. For example, shut- ting down or starting up the UPS modules in the parallel system can be done in any sequence. If an overload transfer occurs, the whole system can recover automatically from bypass mode after the overload is cleared.
•The total load of the parallel system can be queried from each module’s liquid crystal display screen.
Figure 14 Parallel system block diagram
Liebert NX UPS | Liebert NX Basic Paralleling Cabinet |
(Field Removable
Jumper for Dual
Input)
480V, 3W Input
480V DC
Battery Input
Bypass
Static
Switch
AC | DC |
DC | AC |
DC |
DC |
IOB1
480V, 3W
UOB Output
RIB = Rectifier Input
Breaker
IOB = Inverter Output
Breaker
MBB = Maintenance
Bypass Breaker
MIB = Maintenance
Isolation Breaker
LDB = Load Distribution
Breaker
UPS Module 2 
IOB2
UPS Module 3 
IOB3
UPS Module 4 
IOB4
30
