8 Parallel System and LBS System
This chapter gives details on the installation of the parallel system and load bus synchronization (LBS) system.
8.1 General
The parallel system is comprise of up to 4 UPS modules of the same power rating and connected in parallel without the need
for a centralized mains static bypass. Instead the bypass static switches of each UPS share the load when the system
transfers to the mains bypass supply.
In a parallel system, each module is internally identical to the single module configuration. A parallel system requires inter
module control signals to manage the load sharing, synchronizing and bypass switching. The control signals are connected
through the parallel cables, which are multicore ribbon cables connected between the units of the system to form a closed
loop.
8.2 System Installation Procedures
The basic installation procedure of a parallel system is the same as that of single module system. The installation of a parallel
UPS should follow the installation procedure for a single UPS module with the additional requirements detailed in this section.
8.2.1 Preliminary checks
Ensure that the selections of the parallel cables are correct, and that the modules are of the same rating, model, and with the
same software and hardware release.
IMPORTANT! Vertiv service personnel must configure each module separately using Vertiv setting software to
achieve coordinated operation of the modules in the parallel system.
8.2.2 Cabinet installation
Place the UPS modules side by side and interconnect as shown in Figure 8.1 on the next page. The output distribution mode
(QE1, QE2 must be configured) shown in Figure 8.1 on the next page is recommended to facilitate maintenance and system
testing.
8 Parallel System and LBS System Proprietary and Confidential ©2023 Vertiv Group Corp. 143
Vertiv™ Liebert® APM2 30 to 120 kVA Modular UPS User Manual
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