OVERVIEW
10
User Manual 10H52246UM60 - Rev. 1 - 01/2017
Chapter 1
Overview
This chapter provides a brief introduction to the features, appearance and components, design concept, parallel
system, operating mode, battery management and battery protection of the Liebert NXC 60kVA UPS (UPS for
short).
1.1
Features
The UPS is connected between a mains power source and a critical load (e.g. a computer) in order to provide a high
quality power supply for the latter. The UPS offers the following advantages:
Increased power quality
The UPS protects its output against variations in the input power supply by means of the internal voltage and
frequency controller.
Mains failure protection
If the input power fails, the UPS will switch to battery mode so that the power supply to the loads is not interrupted.
1.2
Design Concept
1.2.1
System Design
This section introduces the working principle of the single UPS module. The UPS is based on an AC-DC-AC
converter (as shown in Figure 1-1The first conversion stage (AC-DC) uses a three-phase, high frequency rectifier to
convert the three-phase main input (or rectifier input) voltage into the stable DC bus voltage.
Input
Maintenance bypass switch
Bypass input switch
Rectifier input switch
Bypass input
Mains input
Battery charger
Output switch
Automatic inverter switch
Inverter
Rectifier
Static switch
Maintenance bypass
UPS output
Battery
Output
Figure 1-1 Block diagram for working principle of UPS single module
The UPS has its own battery charger and adopts advanced temperature compensation technology to effectively
prolong the battery service life. The inverter mainly uses high power IGBTs, together with advanced SVPWM control
technology, to reconvert the DC bus voltage to AC voltage.
When the mains input is normal, the rectifier and inverter work together to supply the loads and charge the battery.
When the mains input is abnormal, the rectifier stops working, and the battery supplies power to the loads through
the inverter. If the battery voltage falls to the end of discharge (EOD) voltage and the mains has not yet been
restored, the UPS will shut down (if the system uses split bypass configuration and the bypass is normal, the system
will transfer to bypass). The battery EOD voltage is preset. When the mains is abnormal, the battery guaranteed
normal UPS operation until the battery reaches the EOD voltage, at which point the UPS shuts down: this time is
called 'Backup Time'. The length of backup time depends on the battery capacity and the loads.