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Operating Instructions
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9.7 Battery Protection
9.7.1 Battery Undervoltage Pre-Warning
Before the end of discharge, the Liebert NX displays a Low Battery pre-warning. After this pre-warn-
ing, the battery has the capacity for 5 minutes discharging with full load (default time). The Liebert
NX can be user-configured to display this warning from 3 to 60 minutes before end-of-discharge.
9.7.2 Battery End-of-Discharge (EOD) Protection
If the battery voltage is lower than the end-of-discharge voltage, the battery converter will be shut
down.
9.8 Multi-Module System Procedures
9.8.1 Isolating One Module in a Multi-Module System
1. Turn Off the inverter
2. Open External Output CB4 in Parallel Cabinet (see Figure 60).
The UPS enters Isolation Status automatically, parallel signaling and communication become
masked and output becomes inhibited.
3. Power Off the unit for maintenance.
4. Power On the unit.
5. Unit enters Test Mode by configuration software setting.
6. Diagnosis or testing.
7. The UPS exits Test Mode by configuration software setting.
Output becomes inhibited because of Isolation Status.
8. Return all switches to the Normal position.
9. Close External Output CB4 in Parallel Cabinet (see Figure 60).
The UPS exits Isolation Status automatically, parallel signaling and communication recovers,
output becomes enabled but interlocking works now.
10. Turn On inverter and join the parallel system.
Figure 60 Typical parallel system block diagram with common input supply, with separate batteries and
optional output / bypass distribution panel
NOTE
All equipment servicing procedures must be carried out only by trained personnel.
480V, 3W
System Input
480V, 3W
Output
480V DC
Battery Input
AC
DC
DC
AC
Bypass
Static
Switch
DC
DC
RIB 1
RIB 2
RIB 3
RIB 4 IOB 4
IOB 3
IOB 2
IOB 1
UPS Module 3
MBB
MIB
User Supplied
Plug-In Output
Breakers
480V, 3W
Output
UPS Module 4
UPS Module 2
Liebert NX UPS (40-200kVA)
LDB 1
LDB N
RIB = Rectifier Input
Breaker
IOB = Inverter Output
Breaker
MBB = Maintenance
Bypass Breaker
MIB = Maintenance
Isolation Breaker
LDB = Load Distribution
Breaker