Vertiv LIEBERT NXC 60KVA Installation and maintenance instructions

LIEBERT® NXC™ 60KVAUPS
Reliable & Scalable power system designed
for Small and Mid-size Enterprises
Installer/User Guide

Liebert NXC 60kVA UPS
User Manual
Version
Revision date
V1.5
November 15, 2018
BOM
31013299
Vertiv Tech provides customers with technical support. Users may contact the nearest Vertiv local sales
office or service center.
2015 Copyright © 2017 by Vertiv Tech Co., Ltd.
All rights reserved. The contents in this document are subject to change without notice.
Vertiv Tech Co., Ltd.
Address: Block B2, Nanshan I Park, No.1001 Xueyuan Road, Nanshan District, Shenzhen, 518055,
P.R.China
Homepage: www.Vertivnetworkpower.com
E-mail: [e-mail]

Special Declaration
Personnel Safety
1. This product must be installed and commissioned by professional engineers of the manufacturer or
its authorized agent. Failure to observe this could result in product malfunction or personnel safety
risk.
2. Take the time to read this product manual and the safety precaution thoroughly before installing
and commissioning this product. Failure to observe this could result in product malfunction or
personnel safety risk.
3. This product is not intended for life support equipment application.
4. Never dispose of the internal or external battery of this product in a fire, as it may explode and
jeopardize personnel safety when exposed to flame.
Product Safety
1. If this product will be stored or remain de-energized for a long period, it must be placed in a dry and
clean environment within specified temperature range.
2. This product should be used in an appropriate operating environment. For details, refer to the
section on the environmental requirement in this manual.
3. This product is not designed for application in an environment:
Where the temperature and relative humidity are outside the specifications
Subject to vibrations or shocks
Where conductive dusts, corrosive gases, salts, or flammable gases are present
Near heat sources or strong electromagnetic interferences
Disclaimer
Vertiv disclaims any and all responsibility or liability for the defects or malfunction caused by:
Application range or operating environment outside the specifications
Unauthorized modification, improper installation or operation
Force majeure
Other actions not in compliance with the instructions in this manual

Safety Precaution
Always observe the following safety symbols!
Used to alert the user to the risk of death or severe injury should the unit be used improperly.
Used to alert the user to the risk of injury or equipment damage should the unit be used improperly.
Used to advise the user to carefully read and observe this unit though it may not cause damage.
This manual contains information concerning the installation and operation of single UPS module and
parallel system of the Vertiv NXC 60kVA UPS.
Read this manual thoroughly before installing, using and servicing the UPS.
Note
Notes to the CE Declaration of Conformity
The UPS conforms to the following European directives:
2014/35/EU - Directive of the council for adapting the legal regulations of member states on electrical
equipment for use within specific voltage limits (superseding the 2006/95/EC and successive amendments).
2014/30/EU -
Directive of the council for adapting the legal regulations of member states on electromagnetic
compatibility, (superseding the 2004/108/EC and successive amendments).
Conformity is established through compliance with the following standards:
*IEC/EN 62040-1+A1:2013
*IEC/EN 62040-2:2006
Additional information regarding adherence to these directives is included in the appendices NSR and EMC to
the Declaration of Conformity. If needed, the Declaration of Conformity can be requested to Vertiv.
Warning
System without C2 EMI filter: This UPS is a product for commercial and industrial application in the second
environment. Installation restrictions or additional measures may be required to prevent disturbances.
Warning
System with C2 EMI filter: This UPS is a category C2 UPS product. In a residential environment, this product
may cause radio interference, in which case the user may be required to take additional measures.
Conformity and standards
This product complies with CE 2006/95/EC (low voltage safety) and 2004/108/EC (EMC), EMC standards of
Australia and New Zealand (C-Tick), and the following UPS product standards:

* IEC62040-1 General safety requirements for UPS
*IEC62040-2-EMC
* IEC62040-3 Performance requirements and test methods
For details, refer to Chapter 11 Specifications.
Continued compliance requires installation in accordance with these instructions and the use of manufacturer
approved accessories only.
Warning
The selection of the upstream distribution protection equipment of the UPS shall be selected in accordance
with the details in 3.1.4 Selection Of UPS I/O Switch and shall comply with the local electrical regulations.
Warning: high earth leakage current
Earth connection is critical before connecting the input supply (including both mains supply and battery).
This equipment is installed with an EMC filter.
Earth leakage current is 0 ~ 1000mA.
Transient and steady state earth leakage currents, which may occur when the equipment is started, should be
taken into account in the selection of instantaneous RCCBs or RCD devices.
RCCB which is sensitive to unidirectional DC pulse (Class A) and insensitive to transient state current pulse
must be selected.
Note also that the earth leakage currents of the load will be carried by the RCCBs or RCDs.
The equipment must be earthed in accordance with the local electrical authority code of practice.
General safety precautions (For users)
Like other types of large power equipment, the UPS and battery circuit breaker box/battery cabinet have high
voltage inside. Because the components with high voltage can be accessed only when the front door (which is
locked) is opened, the risk of contacting high voltage has been minimized. This equipment meets the IP20
standard, and other safety shields are provided inside the equipment.
There will not be any danger when operating this equipment according to the general instructions and the
steps recommended in this manual.
Multiple power inputs (For users)
This UPS system receives power from more than one source. Disconnection of all AC source and the DC
source is required before servicing.
This UPS has several circuits that are energized with high AC as well as DC voltages. Check for voltage with
both AC and DC voltmeters before working within the UPS.
User serviceable components (For service personnel)
All equipment maintenance and servicing procedures involving internal access requires the use of a tool and
should be carried out only by trained personnel. There are no user-
serviceable parts behind covers requiring a
tool/key for removal.
Battery voltage: 300Vdc ~ 564Vdc (For service personnel)

All physical battery maintenance and servicing procedures requires the use of a tool and should be carried out
only by trained personnel.
Take special care when working with the batteries associated with this UPS. When connected together, the
battery terminal voltage will exceed 300Vdc and is potentially lethal.
Battery manufacturers supply details of the necessary precautions to be observed in working on, or in the
vicinity of, a large bank of battery cells. These precautions should be followed implicitly at all times. Particular
attention should be paid to the recommendations concer
ning local environmental conditions and the provision
of protective clothing, first aid and fire-fighting facilities.
Warning
When the internal fuse of the UPS is damaged, it must be replaced with fuse of the same electric parameters
by qualified personnel.
Important
Beside the communication board is a static sensitive area, ESD-proof action is critical before contacting with
this area.

The Manual Describes The Following Equipment
Product
Model
Liebert NXC 60kVA
NX 0060kTJ1AFN02000

Revision Information
V1.0 (June 1, 2015)
Initial release.
V1.1 (August 19, 2015)
Change Figures 6-1, 8-2, 8-3 and 8-4; update Table 11-8.
V1.2 (October 18, 2015)
Update the notice to Table 3-2 and Table 3-3; add Sections 8.2.12, 8.2.13 and 8.2.14.
V1.3 (June 10, 2017)
Enrich contents in Section 2.7.2 and Section 6.2; update Appendix 3.
V1.4 (November 15, 2017)
Update related information about Vertiv.
V1.5(November 15, 2018)
Update Figure 6-4 and Table 6-5

Contents
Chapter 1 Overview ........................................................................................................................................1
1.1 Features ......................................................................................................................................................... 1
1.2 Design Concept ............................................................................................................................................. 1
1.2.1 System Design ................................................................................................................................................... 1
1.2.2 Bypass ................................................................................................................................................................ 2
1.2.3 System Control Principle ................................................................................................................................. 2
1.2.4 UPS Power Supply Switch Configuration ...................................................................................................... 4
1.2.5 Battery Circuit Breaker (BCB) ......................................................................................................................... 4
1.3 Parallel System .............................................................................................................................................. 4
1.3.1 Parallel System Features .................................................................................................................................. 4
1.3.2 Parallel System Requirements ........................................................................................................................ 5
1.4 Operation Modes ........................................................................................................................................... 5
1.5 Battery Management ..................................................................................................................................... 8
1.5.1 Normal Function ................................................................................................................................................ 8
1.5.2 Advanced Function .......................................................................................................................................... 9
1.5.3 Battery Temperature Compensation............................................................................................................10
1.6 Battery Protection ........................................................................................................................................10
Chapter 2 Mechanical Installation ................................................................................................................. 11
2.1 Precautions ..................................................................................................................................................11
2.2 Transportation .............................................................................................................................................11
2.3 Tools ............................................................................................................................................................12
2.4 Unpacking....................................................................................................................................................13
2.5 Initial Inspection...........................................................................................................................................14
2.6 Environmental Requirement .........................................................................................................................15
2.6.1 UPS Location Selection ..................................................................................................................................15
2.6.2 Battery Location Selection ...........................................................................................................................15
2.6.3 Storage ............................................................................................................................................................15
2.7 Mechanical Requirement ..............................................................................................................................16
2.7.1 Moving Cabinet ...............................................................................................................................................16
2.7.2 Clearance ........................................................................................................................................................16
2.7.3 Cable Access Mode ........................................................................................................................................16
2.7.4 Final Positioning And Fixing .........................................................................................................................16
2.8 Installation Drawings ...................................................................................................................................18
Chapter 3 Electrical Installation .................................................................................................................... 20
3.1 Wiring Of Power Cable ..................................................................................................................................20

3.1.1 System Configuration .....................................................................................................................................20
3.1.2 Maximum Steady State AC And DC Currents .............................................................................................20
3.1.3 Recommended CSA Of UPS Cable ................................................................................................................21
3.1.4 Selection Of UPS I/O Switch .........................................................................................................................21
3.1.5 Distance Between The UPS Connection Point And The Floor ..................................................................21
3.1.6 Notes ................................................................................................................................................................22
3.1.7 Power Cable Connecting Terminal ...............................................................................................................22
3.1.8 Protection Ground ..........................................................................................................................................22
3.1.9 External Protective Device ............................................................................................................................22
3.1.10 Power Cable Connection Steps ...................................................................................................................23
3.2 Wiring Of Signal Cable .................................................................................................................................29
3.2.1 Overview ..........................................................................................................................................................29
3.2.2 Input Dry Contact Port ..................................................................................................................................29
3.2.3 BCB Port ..........................................................................................................................................................30
3.2.4 Backfeed Protection Dry Contact Port .......................................................................................................31
3.2.5 Remote EPO Input Port .................................................................................................................................31
3.2.6 RS232 Communication Port ..........................................................................................................................32
3.2.7 USB Communication Port ..............................................................................................................................32
3.2.8 Parallel And LBS Communication Ports ......................................................................................................32
3.2.9 RS485 Communication Port ..........................................................................................................................32
3.2.10 Intellislot Port ...............................................................................................................................................33
3.2.11 Signal Cable Connection Steps....................................................................................................................33
Chapter 4 Operator Control And Display Panel .............................................................................................. 36
4.1 Introduction..................................................................................................................................................36
4.1.1 LED Indicators .................................................................................................................................................36
4.1.2 Audible Alarm (Buzzer) .................................................................................................................................37
4.1.3 Control Keys ...................................................................................................................................................37
4.1.4 LCD And Menu Keys ......................................................................................................................................37
4.2 LCD Screen Type .........................................................................................................................................38
4.2.1 Start Screen ....................................................................................................................................................38
4.2.2 Primary Screen ...............................................................................................................................................38
4.2.3 Default Screen ................................................................................................................................................39
4.3 Detailed Description Of Menu Items ............................................................................................................39
4.4 Prompt Window ...........................................................................................................................................43
4.5 Alarm List ....................................................................................................................................................43
Chapter 5 UPS Operation Introduction .......................................................................................................... 47
5.1 Brief Introduction .........................................................................................................................................47
5.1.1 Precautions ......................................................................................................................................................47
5.1.2 Power Switch...................................................................................................................................................47

5.2 UPS Startup Procedures ..............................................................................................................................48
5.2.1 Startup Procedures In Normal Mode ............................................................................................................48
5.2.2 Startup Procedures In ECO Mode ................................................................................................................49
5.2.3 Startup Procedures In Battery Mode (Battery Cold Start) .......................................................................49
5.3 Procedures For Transfer Between Operation Modes ...................................................................................50
5.3.1 Transfer From Normal Mode To Battery Mode ...........................................................................................50
5.3.2 Transfer From Normal Mode To Bypass Mode ...........................................................................................50
5.3.3 Transfer From Bypass Mode To Normal Mode ...........................................................................................50
5.3.4 Transfer From Normal Mode To Maintenance Mode .................................................................................50
5.3.5 Transfer From Maintenance Mode To Normal Mode .................................................................................51
5.4 Battery Test Procedures ..............................................................................................................................52
5.5 UPS Self-test Procedures.............................................................................................................................53
5.6 UPS Shutdown Procedures ..........................................................................................................................53
5.6.1 Procedures For Completely Powering Down UPS ......................................................................................53
5.6.2 Procedures For Completely Powering Down UPS While Maintaining Power To Load ...........................54
5.7 EPO Procedures ...........................................................................................................................................54
5.8 UPS Reset Procedures After EPO ................................................................................................................54
5.9 Automatic Restart........................................................................................................................................55
5.10 Selecting Language ....................................................................................................................................55
5.11 Changing Current Date And Time ...............................................................................................................55
5.12 Control Password .......................................................................................................................................56
Chapter 6 Battery ........................................................................................................................................ 57
6.1 Introduction..................................................................................................................................................57
6.2 Safety ..........................................................................................................................................................57
6.3 UPS Battery .................................................................................................................................................59
6.4 Precautions For Installation Design .............................................................................................................60
6.5 Battery Installation Environment And Number Of Batteries ........................................................................60
6.5.1 Installation Environment................................................................................................................................60
6.5.2 Number Of Batteries......................................................................................................................................61
6.6 Battery Protection .......................................................................................................................................61
6.7 Battery Installation And Connection ............................................................................................................61
6.7.1 Battery Installation .........................................................................................................................................61
6.7.2 Battery Connection ........................................................................................................................................62
6.8 Design Of Battery Room ..............................................................................................................................63
6.9 BCB Box (Optional) ......................................................................................................................................64
6.10 BCB Reference Current And Connection ....................................................................................................66
6.11 Battery Maintenance ...................................................................................................................................67
6.12 Disposal Of Used Battery ...........................................................................................................................68

Chapter 7 Parallel System And LBS System ................................................................................................... 69
7.1 General .........................................................................................................................................................69
7.2 System Installation Procedures ....................................................................................................................69
7.2.1 Preliminary Checks .........................................................................................................................................69
7.2.2 Cabinet Installation ........................................................................................................................................69
7.2.3 Power Cable ....................................................................................................................................................70
7.2.4 Parallel Cable ..................................................................................................................................................70
7.2.5 Remote EPO ....................................................................................................................................................71
7.3 Operation Procedures For Parallel System ...................................................................................................72
7.3.1 Startup Procedures In Normal Mode ............................................................................................................72
7.3.2 Maintenance Bypass Procedures .................................................................................................................73
7.3.3 Procedures For Isolating One UPS Module From Parallel System ...........................................................74
7.3.4 Procedures For Inserting One Isolated UPS Module In Parallel System ..................................................74
7.3.5 Procedures For Completely Powering Down UPS ......................................................................................75
7.3.6 Procedures For Complete UPS Shutdown While Maintaining Power To Load........................................75
7.4 LBS System ..................................................................................................................................................75
7.4.1 Cabinet Installation ........................................................................................................................................75
7.4.2 External Protective Device ...........................................................................................................................77
7.4.3 Power Cable ....................................................................................................................................................77
7.4.4 LBS Cable .......................................................................................................................................................77
Chapter 8 Options........................................................................................................................................ 78
8.1 Option List....................................................................................................................................................78
8.2 Option Introduction .....................................................................................................................................78
8.2.1 Bypass Load Sharing Inductor Kit ................................................................................................................78
8.2.2 Internal Battery Kit ........................................................................................................................................81
8.2.3 Battery Temperature Compensation Kit .....................................................................................................87
8.2.4 Seismic Anchor Kit ........................................................................................................................................89
8.2.5 IS-UNITY-DP Card .........................................................................................................................................91
8.2.6 IS-WEBL Card .................................................................................................................................................91
8.2.7 IS-Relay Card ..................................................................................................................................................92
8.2.8 IS-485L Card...................................................................................................................................................94
8.2.9 BCB Box ..........................................................................................................................................................94
8.2.10 Parallel Cables ..............................................................................................................................................94
8.2.11 LBS Cables .....................................................................................................................................................94
8.2.12 C2 Electromagnetic Shielding Assembly ...................................................................................................95
8.2.13 Output Transformer .....................................................................................................................................95
8.2.14 Lightning Proof Box .....................................................................................................................................97
Chapter 9 Communication ............................................................................................................................ 98
9.1 SNMP Protocol Communication....................................................................................................................98

9.2 Modbus Protocol Communication ................................................................................................................98
9.3 Dry Contact Communication ........................................................................................................................98
9.3.1 Communication Through IS-Relay Card ......................................................................................................98
9.3.2 Communication Through Dry Contact Port ................................................................................................99
Chapter 10 Service And Maintenance .......................................................................................................... 100
10.1 Safety ....................................................................................................................................................... 100
10.2 Key Components And Service Life Of UPS ............................................................................................... 100
10.2.1 Life Parameters And The Proposed Replacement Time Of Key Components .................................... 100
10.2.2 Replacement Of Air Filter ......................................................................................................................... 100
10.2.3 Replacement Of Fuse ................................................................................................................................ 101
10.3 Maintenance Of UPS And Options ............................................................................................................ 101
Chapter 11 Specifications ........................................................................................................................... 103
11.1 Conformance And Standards ..................................................................................................................... 103
11.2 Environmental Characteristics .................................................................................................................. 103
11.3 Mechanical Characteristics ....................................................................................................................... 103
11.4 Electrical Characteristics (Input Rectifier) ................................................................................................ 104
11.5 Electrical Characteristics (Intermediate DC Circuit) ................................................................................. 104
11.6 Electrical Characteristics (Inverter Output) .............................................................................................. 105
11.7 Electrical Characteristics (Bypass Input) .................................................................................................. 105
11.8 Efficiency And Loss................................................................................................................................... 107
Appendix 1 Disposal Of Old Appliances ....................................................................................................... 108
Appendix 2 Glossary .................................................................................................................................. 109
Appendix 3 Hazardous Substances And Content ......................................................................................... 110

Chapter 1 Overview 1
Liebert NXC 60kVA 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 60kVA 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:
Augment power quality
The UPS protects its output against the input power change through the internal voltage and frequency
controller.
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.
Input
Maintenance bypass switch
Bypass input switch
Rectifier input switch
Bypass input
Mains input
Battery charger
Output switch
Automatic
inverter switch
InverterRectifier
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 adopts large power IGBT, and adopts
advanced SVPWM technology for control, to invert the DC bus voltage back to AC voltage.

2Chapter 1 Overview
Liebert NXC 60kVA UPS User Manual
When the mains is normal, the rectifier and inverter work together to supply the loads and charge the
battery.
When the mains is abnormal, the rectifier stops working, and the battery supplies power to the loads
through the inverter. If the battery voltage falls to end of discharge (EOD) voltage and the mains still has
not been recovered, 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 maintains the UPS operation till the battery voltage is reduced to EOD voltage and
the UPS shuts down, this time is called 'Backup Time'. The length of backup time depends on the battery
capacity and the loads.
1.2.2 Bypass
Through the intelligent control of the 'Static Switch' module (as shown in Figure 1-1) containing the
controllable electronic switch, the loads can be supplied by the inverter or the bypass. In normal situation,
the loads are supplied by the inverter, in which case the automatic inverter switch at inverter side is
closed. In the case of overload (the overload delay time expires) or inverter failure, the inverter switch is
opened, and the 'Static Switch' module will automatically transfer the loads to the bypass.
In normal operating state, to realize the uninterrupted transfer between inverter and bypass, the inverter
output must be synchronized with the bypass.
Therefore, when the bypass frequency is within the synchronization range, the inverter control circuit will
synchronize the inverter output frequency with the bypass frequency and phase.
Besides, the UPS has a manual maintenance bypass switch for shutdown of the UPS upon maintenance. In
this situation, the bypass will directly supply the critical loads through the maintenance bypass.
Note
When the load is supplied by the bypass or maintenance bypass, the power quality & availability will be unregulated.
1.2.3 System Control Principle
Normal operation
Normal mode: It means that the UPS has normal input mains, the rectifier and inverter operate normally,
the load is supplied by the inverter, the battery circuit breaker is closed, and the battery is in stable
floating charge state.
(Parallel System) Note: As the UPS single module outputs are connected in parallel, the system checks
that the inverter control circuits are perfectly synchronized with one another and with the bypass in terms
of both frequency and phase, and that they have the same output voltages. Current supplied to the load is
automatically divided among UPSs. A warning message appears while synchronization is in progress.
Mains abnormal
When the mains fails or is abnormal, the rectifier will stop working automatically, and the system will
transfer to battery output (through inverter). The length of the operation time in battery mode depends
on the load and the battery capacity. During this period, if the battery voltage falls to the EOD voltage and
the mains still has not been recovered, the inverter will stop working automatically, and the UPS operator
control and display panel will display corresponding alarm messages. If the system uses split bypass
configuration and the bypass is normal, the system will transfer to bypass.

Chapter 1 Overview 3
Liebert NXC 60kVA UPS User Manual
Mains recovery
When the mains resumes normal within allowable time, the rectifier will start automatically (at this time its
output power will increase gradually) and supply the load and charge the battery again. Therefore, the
power supply to the load will not be interrupted.
Battery disconnection
To disconnect the external battery from the UPS system for maintenance, use the external isolation
device. At this time, except for the battery backup function upon mains failure, other functions and all the
steady state performance of the UPS will not be affected.
UPS module failure
In case of inverter failure, inverter switch failure, output fuse blowout and bypass STS failure, the load will
automatically transfer to the bypass, and the output power supply will not be interrupted. In this situation,
please contact the local customer service center of Vertiv Tech Co., Ltd for technical support.
(Parallel System) In the event of a fault in a UPS module, it will automatically exit from the parallel system.
If the system is still capable of providing the required load, the remaining modules will continue to supply
the load with no interruption. If the remaining modules are no longer capable of fulfilling power
requirements, the load will automatically transfer to the bypass.
Overload
If the inverter is overloaded or the inverter current remains outside the specifications (refer to Table 11-6)
longer than the specified time, the load will automatically transfer to the bypass without power
interruption. If both the overload and the current are reduced to a level within the specified range, then
the load will be transferred back to the inverter. In case of output short circuit, the load will be transferred
to the bypass, and the inverter will shut down. Five minutes later, the inverter will start up automatically. If
the short circuit is removed at this point, the load will be transferred back to the inverter. The transfer is
determined first of all by the features of the protective device of the system.
In the above two situations, the UPS operator control and display panel will display alarm messages.
(Parallel System) The control logic system constantly monitors load requirements and controls the power
supplied by each UPS module. In the event that an overload condition is sustained for greater than a
preset time, the load will transfer to the bypass, when the number of active modules is unable to satisfy
load requirements. The load returns to the inverter if the power is reduced to a value that can be
sustained by the number of active modules in the system.
Maintenance bypass
The UPS has a second bypass circuit, i.e. maintenance bypass, which provides a safe working environment
for the engineers to provide regular maintenance or repair to the UPS system and at the same time
provide unregulated mains supply to the loads. The maintenance bypass can be manually selected
through the maintenance bypass switch, and it can be disconnected by turning the switch to OFF.
Warning
If the UPS system is composed of two or more UPS modules, and the load capacity exceeds the single module
capacity, do not use the internal maintenance bypass switch.

4Chapter 1 Overview
Liebert NXC 60kVA UPS User Manual
1.2.4 UPS Power Supply Switch Configuration
Figure 1-2 describes the block diagram of the UPS module. The UPS has split bypass configuration (that is,
the bypass adopts independent mains input) and common input configuration. In split bypass
configuration, the static bypass and maintenance bypass share the same independent bypass power
supply. Where a separate power source is not available, the input supply connections of the bypass input
switch (Q2) and rectifier input switch (Q1) would be linked together (linked before delivery) to make the
bypass input and rectifier input use mains power of the same route.
During the normal operation of the UPS, except for the maintenance bypass switch Q3, other switches
shall be closed.
Bypass input
Mains input
Neutral line input
Battery BCB
Rectifier Inverter
Charger
DC bus
UPS
Maintenance bypass switch Q3
Bypass input switch Q2
Rectifier input
switch Q1
Static switch
Automatic
inverter switch
Output switch Q5
UPS output
Neutral line
output
Shorting copper
bar of common
input configuration
Neutral line
switch Q6
Neutral line
Figure 1-2 UPS power supply switch configuration
1.2.5 Battery Circuit Breaker (BCB)
The external battery shall be connected to the UPS through the BCB. The BCB box is an option, which
shall be installed near the battery. The BCB is closed manually or electrically. The BCB has undervoltage
tripping coil. Upon battery undervoltage, the UPS control circuit will send a signal to the coil to trip the
BCB. It also has a magnetic trip facility for overload protection.
1.3 Parallel System
Up to four UPS modules can be parallel-connected to form a parallel system to increase the system
capacity and reliability. The load is equally shared between the paralleled UPS modules.
Moreover, two UPS modules or parallel system can comprise a dual bus system (LBS). Each UPS module
or parallel system has independent output. Output synchronization is achieved through the LBS cable,
thus enabling seamless load transfer between the two systems.
1.3.1 Parallel System Features
1. The hardware and software of parallel system are completely the same as those of the single module.
The parallel system configuration is achieved through settings in configuration software or panel buttons.
2. Parallel cables are connected in a ring, providing both system reliability and redundancy. LBS cables are
connected between any two UPS modules of each bus. The intelligent parallel logic provides the user with

Chapter 1 Overview 5
Liebert NXC 60kVA UPS User Manual
maximum flexibility. For example, shutting down or starting up UPS modules in a parallel system can be
done in any sequence. Transfers between normal mode and bypass mode of operation are seamless and
self-recoverable, that is, the overload is cleared, and the system will be automatically recovered to its
original operation mode.
3. The total load of the parallel system can be queried from each UPS module's LCD.
1.3.2 Parallel System Requirements
A group of paralleled modules behave as if it were one large UPS with the advantage of presenting higher
reliability. To ensure that all modules are equally utilised and to comply with relevant wiring rules, the
following requirements apply:
1. All UPS modules must be of the same rating and must be connected to the same bypass source.
2. The bypass and rectifier input sources must be connected to the same neutral line input terminal.
3. Any RCD, if installed, must be of an appropriate setting and located upstream of the common neutral
line input terminal. Alternatively, the device must monitor the protective earth current of the system. Refer
to Warning: high earth leakage current before Contents.
4. For parallel system consists of two or more UPS modules, the bypass load sharing inductors (optional)
should be selected.
1.4 Operation Modes
The UPS has the following operation modes:
Normal mode
Battery mode
Automatic restart mode
Bypass mode
Maintenance mode
ECO mode
Parallel redundancy mode (system expansion)
LBS system mode
Common battery string mode
Frequency converter mode
Normal mode
As shown in Figure 1-3, the mains is rectified by the UPS rectifier and then inverted by the inverter to
supply uninterrupted AC power to the loads. At the same time, the charger will charge the battery.
Rectifier input switch
Mains input
Battery charger
Output switch
InverterRectifier
UPS output
Battery
Automatic inverter switch
Figure 1-3 Schematic diagram of normal mode