Emerson 250-400kVA - Manual (Page 8)

Introduction
2
1.0 I
NTRODUCTION
1.1 General Description
The Liebert NXL UPS provides continuous, high-quality AC power to your business-critical equip-
ment, such as telecommunications and data processing equipment. The Liebert NXL UPS supplies
power that is free of the disturbances and variations in voltage and frequency common to utility
power, which is subject to brownouts, blackouts, surges and sags.
The Liebert NXL utilizes the latest in high-frequency, double-conversion pulse-width modulation
technology and fully digital controls to enhance its reliability and increase the ease of use.
As shown in Figure 1, the AC utility source is input at CB1 and the rectifier converts the AC utility
into DC power. The inverter converts that DC power from the utility—or DC power from the batter-
ies— into AC power for the load. The batteries power the load through the inverter in the event of a
power failure. The utility source can also power the load through the static bypass.
If maintenance or repair of the UPS is necessary, the load can be switched without interruption in
service to the maintenance bypass.
Figure 1 Typical UPS system one-line diagram
1.2 Modes of Operation
1.2.1 Normal Mode
Operating in normal mode, the Liebert NXL’s rectifier derives power from a utility AC source and
supplies regulated DC power to the inverter, which regenerates precise AC power to supply the con-
nected equipment. The rectifier also uses the utility source power to charge the batteries.
Bypass
Input
Battery
System
DC Bus
BFB
CB2 CB1
MBD
Module
Output