8.2.3 External protective device
WARNING! High earth leakage current. Earth connection is essential before connecting the input supply
(including both mains supply and battery). The equipment must be earthed in accordance with the local
electrical regulations.
8.2.4 Power cable
The power cable wiring is done same as that of a single UPS module. Refer to Wiring of Power Cable on page33.
The bypass and rectifier should be connected with same neutral line input terminal. The current leakage protective device
must be installed on the upstream of the neutral line input terminal.
NOTE: The power cables (the bypass input cable and the UPS output cable) of each UPS module should be of the
same length and specifications to facilitate load sharing.
8.2.5 Parallel cable
The cables must be interconnected in a ring shaped connection between the UPS modules, as shown in Figure 8.2 below. The
ring connection ensures the reliability of the control of the parallel system.
NOTE: Shielded and double insulated parallel cables are available in lengths of 5 m, 10 m and 15 m.
The specific connection method is: The parallel cable of one single UPS is connected from the DB15 port of the
communication box to the DB15 port of the immediate next single machine communication box and is in sequence. Make sure
to check all the reliable cable connections before starting up the UPS system.
Figure 8.2 Parallel Signal Cables Connection (Parallel System)
8.2.6 Remote emergency power OFF (EPO)
In addition to the EPO switch provided on the operator control and display panel of each UPS module for controlling the EPO
of each module respectively, the parallel system also provides remote EPO function for controlling all UPS modules to
shutdown simultaneously from a remote terminal, as shown in Figure 8.3 on the next page.
NOTE: The remote EPO switch must provide dry contact signal, which is normally open or normally closed. The open
circuit voltage provided is 12 VDC, <20 mA.
8 Parallel System and LBS System Proprietary and Confidential ©2023 Vertiv Group Corp. 145
Vertiv™ Liebert® APM2 30 to 120 kVA Modular UPS User Manual
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