N O T E: Q 1, Q 2 and Q 5 are optional while Q 3 is stand ard.
N O T E: T he m ains input and byp ass input share the sam e neutral line.
2.2.5 Battery Circuit Breaker (BCB)
The external battery shall be connected to the UPS through the BCB. The BCB box is optional, which shall be installed near
the battery. The BCB is closed manually. The BCB has a shunt tripping coil. When the system is faulty and the BCB needs to be
disconnected, the UPS control circuit will send a signal to the shunt tripping coil so as to trip the BCB. It also has a magnetic
trip facility for overload protection and short circuit protection.
2.3 Parallel System
Up to six 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 TOUCHSCREEN.
2.3.2 Parallel System Requirements
A group of paralleled modules behave as if it were 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 the same series, and connect to the same bypass source.
2. The N line of bypass and rectifier input sources must be connected to the same neutral line 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: Earth connection is critical before connecting the input supply (including both mains
supply and battery). on page2
2 Overview
13
Vertiv™ Liebert® EXM2 UPS User Manual
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