Vertiv Liebert APM Plus - 2.3 Parallel System

2.3 Parallel System
Up to four UPS modules can be parallel-connected to form a parallel system to increase the system capacity and reliability.
The load is equally shared between the paralleled UPS modules.
Moreover, two UPS modules or parallel system can comprise a dual bus system. Each parallel system has independent output.
Output synchronization is achieved through the LBS cable or LBS device, thus enabling seamless load transfer between the
two parallel systems or single modules through the STS device.
2.3.1 Parallel System Features
1. The hardware and software of parallel system are completely the same as those of the single module. The
parallel system configuration is achieved through settings in configuration software.
2. Parallel cables are connected in a ring, providing both system reliability and redundancy.
3. The total load of the parallel system can be queried from each UPS module's TOUCH SCREEN.
2.3.2 Parallel System Requirements
A group of paralleled modules behaves as one large UPS with the advantage of presenting higher reliability. To ensure that all
modules are equally utilized and to comply with relevant wiring rules, the following requirements apply:
1. All UPS modules must be of the same series, and connected to the same bypass source.
2. The bypass and rectifier input sources must be connected to the same neutral line input terminal.
3. Any RCD, if installed, must be of an appropriate setting and located upstream of the common neutral line input
terminal. Alternatively, the device must monitor the protective earth current of the system. Refer to Warning:
High earth leakage current on page3 .
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Vertiv™ Liebert® APM Plus User Manual