Introduction; General Description; Modes Of Operation; Normal Mode - Emerson Liebert NXL series Operation And Maintenance Manual

Liebert NXL UPS

1 INTRODUCTION

1.1 General Description

The Liebert NXL UPS provides continuous, high-quality AC power to your
business-critical equipment, 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 Q1 and the rectifier
converts the AC utility into DC power. The inverter converts that DC power
from the utility—or DC power from the batteries— 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.
Bypass
Mains
Supply
Input
Input
Isolator Q1
Mains
Supply
Battery

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 connected equipment. The rectifier
also uses the utility source power to charge the batteries.
Page 11
Operation and Maintenance Manual
Maintenance Bypass Isolator Q3
Bypass Isolator Q2
DC Bus
RECTIFIER INVERTER STATIC SWITCH
C.B.
Battery Circuit
Breaker
250-300-400-800kVA
UPS MODULE
Bypass Side
Output
UPS
Isolator Q4
Output