User Guide

Parallel System and LBS System Installation
Liebert
®
APM
™
38
4.0 PARALLEL SYSTEM AND LBS SYSTEM INSTALLATION
This chapter gives details on the installation of a parallel system and an LBS system.
4.1 General
A parallel Liebert APM system can consist of two Liebert APM cabinets connected in parallel without
a main system static bypass. Instead, the bypass static switches of each UPS share the load when the
system transfers to the utility bypass supply. A third-party APM paralleling switchboard may be used
to provide external maintenance capability. See Figure 23 for details.
From a power viewpoint, each module is internally identical to the single-module configuration. A
parallel system requires intermodule control signals to manage the load sharing, synchronizing and
bypass switching. The control signals are connected through parallel communication cables, which
provide bi-directional communication between the two Liebert APM units of the system. A second
parallel cable is provided to establish redundancy.
When Liebert APM units are to be connected in parallel, a sharing inductor assembly is required and
must be installed inside the Liebert APM cabinet. The inductor may be installed at the factory or
field-installed.
4.2 System Installation Procedures
The installation of a parallel UPS should follow the procedures for a single UPS module with the
additional requirements detailed in this section.
4.2.1 Preliminary Checks
Be sure that the options of the parallel cables are correct and that the modules are of the same rating,
model and with the same software and hardware release.
4.2.2 Cabinet Installation
Position the UPS modules and make connections as shown in Figure 23. The output distribution
consisting of external UPS output switches and maintenance bypass must be installed, as shown in
Figure 23, to facilitate maintenance and system testing.
!
WARNING
To achieve coordinated operation of the modules in the parallel system, it is required to
configure each module separately using Emerson configuration software. This must be done
by Emerson service personnel.