Introduction; General Description; Modes Of Operation; Normal Mode - Vertiv Liebert NXL Series Operation And Maintenance Manual

1.0 INTRODUCTION

1.1 G D
ENERAL ESCRIPTION
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 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 DC source— into AC power for the
load. The DC source will 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
optional maintenance bypass.
Figure 1 Typical single module UPS system one-line diagram
Bypass
Input
CB1
DC Source
1.2 M O
ODES OF PERATION
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 DC sources.
1.2.2

Bypass Mode

When the Liebert NXL is in bypass mode, the load is directly supported by utility power and is without DC source
backup protection.
The Liebert NXL's inverter and bypass static switch will shift the load from the inverter to bypass mode without
an interruption in AC power if the inverter is synchronous with the bypass and any of the following occurs:
• Inverter fails
• Inverter overload capacity is exceeded
• Inverter is manually turned off by the user
Vertiv | Liebert ® ™
NXL
BFB
MBD
250-1100kVA, 60Hz, Three Phase, SMS & MMS UPS Operation and Maintenance Manual
DC Bus
Introduction
Module
Output
CB2
2