Chapter 7 Dual Bus System 53
Liebert APM 90 Integrated Modular UPS User Manual
Chapter 7
Dual Bus System
This chapter introduces the installation and operating of the dual bus system.
7.1
Installation Of Dual Bus System
7.1.1
Cabinet Installation
As shown in Figure 7-1, a dual bus system consists of two independent UPS systems. Each UPS system may be
a UPS module or a parallel system consisting of two parallel UPS modules. The dual bus system has high
reliability and is suitable for load with multiple input terminals. For single-input load, an STS can be fitted to
feed power to the load.
Rectifier
Q1
Q2
Q3
Q5
STS
Q1
Q2
Q3
Q5
LBS
Rectifier
Bypass
Bypass
Rectifier
Rectifier
Q1
Q2 Q3
Q5
Q1
Q2
Q3
Q5
LBS
STS
To load
Figure 7-1
Typical dual bus system (with STS and LBS)
The dual bus system uses the LBS cable/adapter to keep the output of the two independent UPS systems (or
parallel systems) in synchronization. One system is designated as the master, the other is designated as the
slave. The operation modes of the parallel system comprise master and/or slave operation in normal or bypass
mode.
Place the UPS modules side by side and interconnect the UPS modules according to the following instructions.
7.1.2
External Protective Device
Refer to
3.1.7 External Protective Device
.
7.1.3
Power Cable
The wiring of power cables is similar to that of single module system. The bypass and the main input sources
must be referenced to the same neutral potential, and the input earth leakage monitoring devices, if installed,
must be located upstream of the common neutral sinking point.
