Chapter 8 Parallel System
Chapter 8 Parallel System
8.1 System Introduction
8.1.1 Basics
The Liebert UPS uses intelligent and reliable decentralized parallel operation technology. A maximum of four single units of the same capacity can operate in parallel.
The UPS system has two paralleling modes:
Paralleling for redundancy
Paralleling for capacity
1. Conditions for parallel operation
Each UPS unit has the same capacity, same software and hardware version
Each UPS in the system must share the same bypass source
The UPS output are connected together. The rectifier input can be from a different source, but the phase rotation of the rectifier input, bypass input and output must be the same
The parallel logic cable and load sharing cable must be connected
2. Features of parallel systems
1）The hardware and firmware of each unit in the system must be compatible and changing the operation mode can be done only with changing the software setting.
2）The parallel signal bus is simple, reliable and designed for redundancy, which provides the user with maximum flexibility. Shutting down or starting up the UPS in the parallel system can be done in any sequence. If an overload occurs, the system can recover automatically from bypass mode after the overload is cleared.
3）The operation status can be queried from each UPS’s LCD display.
4）The UPS monitoring module (optional) can monitor the system parameters of the whole system.
5）Any single module UPS system in the parallel system can be designated as the host for communication with remote computer. The total load current, number of
87
