Emerson Liebert NXC User Manual page 36

Liebert NXC
The diagram of three UPS parallel system is shown in Figure 4-1. Refer to Power distribution mode in 3.4.1 for the cable
connection of each UPS. Refer to 3.4 for the measurement of the input, output and battery cables.
Qin
UPS1
Supplied by others
Mains input
L1, L2, L3, N
Rectifier
STS
Inverter
L1, L2, L3, N
UPS 1 output
Qout UPS1
Qout of allUPS
For 1+N installations, an external bypass rated for the total system load must be installed and the UPS internal maintenance bypass must
be locked to prevent it from being operated.
When planning and installing the system, the power cables between input distribution and the Bypass and rectifier must be
the same length (+/- 10%). The same applies to the power cables between the UPS outputs and the parallel connection point
on the load side.
Each UPS must configure extenal input MCB and extenal output MCB when carring out the power distribution for the parallel system, as
shown in Figure 4-1. When operating the external Bypass (Qout BYP) refer to 6.2.6.
Changing power distribution mode
This product is compatible with 3-in 3-out/3-in 1-out, factory default: 3-in 3-out.
Carry out the parallel connection after changing the single system to the required system (refer to Changing power
distribution mode in 3.4.1 for the changing method), if you need to change the mode from 3-in 3-out to 3-in 1-out or from
3-in 1-out to 3-in 3-out.
User Manual 10H52188UM60 - Rev. 2 - 09/2012
Bypass input
Mains input
L1, L2, L3, N L1, L2, L3,
N
L1, L2, L3, N
Output distribution
Figure 4-1 1 + N UPS System with External Maintenance Switch
Parallel UPS Installation And Commissioning
Qin
UPS2
Bypass input Mains input
L1, L2, L3, N L1, L2, L3,
N
Rectifier
STS
Inverter
L1, L2, L3, N
UPS 2 output
Qout UPS2 Qout UPS3
Note
Warning
Qin
Qin Ext
UPS3
Byp
Bypass
input L1,
L2, L3,N
L1, L2, L3
Rectifier
STS
Inverter
UPS 3 output
Qout BYP
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