User manual

24 Chapter 3 Installation Of Parallel System
NXr UPS Module And Parallel System 30kVA ~ 200kVA User Manual
Qout of all UPSs
Rectifier
Inverter
Mains input
L1, L2, L3, N
Qout UPS 1
Supplied by others
Qin UPS 1
STS
Qout UPS 2
Qout UPS 3
Output distribution
Qout Byp
Bypass input
L1, L2, L3, N
Mains input L1,
L2, L3, N
Bypass input
L1, L2, L3, N
Mains input L1,
L2, L3, N
Bypass input
L1, L2, L3, N
L1, L2, L3
Rectifier
STS
Inverter
UPS 1 output
UPS 2 output
L1, L2, L3, N
L1, L2, L3, N
L1, L2, L3, N UPS 3 output
STS
Rectifier
Inverter
Qin UPS 2 Qin UPS 3
Qin Ext
Byp
Figure 3-3 1 + N UPS system with external maintenance switch
Note
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 off to prevent operation.
1. For parallel systems designed for redundancy with 3 or more UPSs, it is recommended to install bypass load
sharing inductors to optimize current sharing during static bypass operation.
2. For parallel systems designed for capacity, with 2 or more UPSs, it is recommended to install bypass load
sharing inductors to optimize current sharing during static bypass operation.
3.2.2 External protective device
Refer to Chapter 1 Installation Of single UPS cubicle .
3.2.3 Power Cable
The wiring of the power cable is similar to that of UPS module. The bypass and main input supplies must use the
same neutral line input terminal. If the input has a current leakage protective device, the current leakage protective
device must be fitted upstream of the common neutral sinking point. Refer to Chapter 1 Installation Of single UPS
cubicle .
Note
The length and specification of power cables including the bypass input cables and UPS output cables should be the same. This
facilitates load sharing in bypass mode.