Chapter 1 Overview 1
Liebert NXC 30kVA And 40kVA UPS User Manual
Chapter 1 Overview
This chapter briefly introduces the features, design concept, parallel system, operation mode, battery management
and battery protection of the Liebert NXC 30kVA and 40kVA UPS (UPS for short).
1.1 Features
The UPS is connected between a critical load (e.g. a computer) and mains power to provide high quality power for the
loads. The UPS has the following advantages:
Increase power quality
The UPS protects its output against the input power change through the internal voltage and frequency controller.
Improve noise rejection
Due to the application of AC-DC-AC conversion mode, the noise in the input power is effectively filtered, and the load
gets clean power supply.
Provide mains failure protection
If the input power fails, the UPS will work in battery mode, and the power supply to the loads will not be interrupted.
1.2 Design Concept
1.2.1 System Design
This section introduces the working principle of the single UPS module. The UPS adopts AC-DC-AC converter (as
shown in Figure 1-1). The first stage conversion (AC-DC) adopts three-phase high frequency rectifier to convert the
three-phase input voltage into stable DC bus voltage.
Figure 1-1 Block diagram for working principle of single UPS module
The UPS has its own battery charger and adopts advanced temperature compensation technology to effectively
prolong the battery service life. The inverter mainly adopts large power IGBT, and adopts advanced SVPWM
technology for control, to invert the DC bus voltage back to AC voltage.
When the mains is normal, the rectifier and inverter work together to supply the loads and charge the battery.
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