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LIEBERTNX 1+1 SYSTEM

PRODUCTSPECIFICATIONANDINSTALLATIONSHEET

General

The Liebert NX UPS uses intelligent and reliabledecentralized technology to achieve parallel opera-tion of two modules of the same rating.

The 1+1 system is used to:

Increase the reliability of the system to ensure

adequate power supply to the critical load con-nected.

Increase serviceability and allow the execution ofmaintenance operations and reparations withoutaffecting the ordinary operating conditions of thesystem (depending on the redundancy level).

Conditions for Parallel System

1. Each UPS module should have the same rating,

the same firmware and hardware version.

2. Each UPS module must have the same bypasssource.

3. The outputs of all UPS modules are connectedaltogether.

4. The main inputs can be from different sources, butthe phase rotation sequence of main inputs,bypass inputs and outputs must be correct and thesame.

5. The parallel logic cable and load sharing cablemust be connected in a ring correctly (SeeFigure 2)

Features of Parallel System

1. The hardware and firmware for parallel UPSmodule operation is standard in the Liebert NX,

and the configuration can be set up by changingthe settings in configuration software.

2. It is easy to install the parallel cables in a ring,providing high reliability and redundancy. Andthe intelligent paralleling logic provides the userwith maximum flexibility. For example, shuttingdown or starting up the UPS modules in theparallel system can be done in any sequence. If anoverload transfer occurs, the whole system canrecover automatically from bypass mode after theoverload is cleared.

3. The total load of the parallel system can bequeried from each modules liquid crystal display

screen.4. Optional monitoring background software can

treat the entire parallel system as a bigsingle-module UPS, and provide correspondingmanagement. It can also get the information for allmodules by connecting to just one of the modules.

+

!CAUTIONAn external maintenance cabinet is strongly

recommended to maintain the power supply to

load in case of complete maintenance.


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Figure 1 '1+1' System block diagram

Operating Principles

Redundancy Paralleling

The redundancy parallel system can noticeablyimprove system reliability. In normal condition, nei-ther UPS module works at full load. That meansthat even if the load is increased, the system will nottransfer to bypass. And when a UPS module shutsdown due to any failure, the remaining UPS modulecan still power and protect the load. When redun-dancy is lost due to module failure or load increase,the parallel system will trigger an alarm.

Operation Modes Summary

The parallel system also has operation modes suchas normal, battery, bypass and maintenance bypass.All UPS modules in the 1+1 parallel system operatein coordination.

Normal Mode OperationThe load is powered by the inverters of all theUPS modules in the system. If the frequency ofbypass is within the synchronous range, theinverter will be synchronized with the bypass.Otherwise, the system will operate at nominalfrequency.

Battery Mode Operation

The batteries of all UPS modules power the loadthrough their inverters. The system operates atnominal frequency.

Bypass Mode Operation

The condition to transfer to bypass mode is thesame as that for a single module system. Thebypass of all the UPS modules powers the load.

Maintenance Bypass Mode Operation

The sequence to transfer to maintenance bypassmode is the same as for transferring a single-module system. The maintenance bypassswitches should be switched on as synchronouslyas possible. Thus the system can be repairedwithout interrupting the power supply to criticalload.

Intermodule Control

Two kinds of signals are used for the parallel cables:

Analog signalsUPS output unbalanced current

Digital signalscontrol logic signals, parallel

cable status

Parallel control cables should be connected to theparallel board (M3) of all modules and form a ring toprovide redundancy as shown in Figure 2.

Two types of Parallel control cables needed:

DB9for analog signals with one end DB9/F andone end DB9/M

DB25for digital signals with one end DB25/F andone end DB25/M

These come in lengths of 5m, 10m, &15m.

Supplied by OthersN N

Input UtilitySupply A B C

Input UtilitySupply A B C

Distribution Panel

UPS1 UPS2CB1 CB1

RectifierRectifier

SW1-C SW1-C

StaticSwitch

StaticSwitch

Charger Charger Battery 2Battery 1

FuseFuse

Inverter Inverter SW1-D SW1-D

SW1-A SW1-A

A B CA B C

Q1EXT Q2EXT

QBYPQUPS

To Load


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Installation

The basic installation procedure of parallel system isthe same as that of single module system. The fol-lowing sections only introduce the installation proce-dures specific to the parallel system.

Cabinet Installation

Parallel system composed of two UPS modules

The two UPS modules that will form the 1+1 systemshould be placed side-by-side. Each battery cabinetis placed next to its corresponding UPS module.

Preliminary Checks

Each UPS module should have the same rating, thesame firmware and the same hardware version.Refer to the instructions in Conditions for Paral-lel System on page 1.

Protective Devices

Refer to the instructions supplied in the Liebert NXinstallation manual, SL-25215.

Power cablesWiring of power cables is similar to that of singlemodule system (see the Liebert NX installation man-ual, SL-25215). The bypass sources of all modulesshould be the same, and the outputs should be con-nected altogether correctly.

Parallel Control CablesMake the connections described below on the paral-lel logic board (M3) inside the Liebert NX:

Connect one end of the DB-25 interconnectingcable to the X2_1 connector of UPS 1 and the otherend to the X2_2 connector of UPS 2.

Connect one end of the DB-25 interconnectingcable the X2_2 connector of UPS 1 and the otherend to the X2_1 connector of UPS 2.

Connect one end of the DB-9 interconnecting cablethe X1_1 connector of UPS 1 and the other end tothe X1_2 connector of UPS 2.

Connect one end of the DB-9 interconnecting cablethe X1_2 connector of UPS 1 and the other end tothe X1_1 connector of UPS 2.

The connections are shown above in Figure 2.

Figure 2 Connecting 1+1 system parallel controlcables

Commissioning a Parallel System

Check the input and output wiring of each UPS mod-ule. Ensure that the phase rotation sequence of themain inputs and the bypass inputs and outputs of

each UPS module are the same. Ensure the parallelcables are connected firmly.

It is assumed that the installation is complete, thesystem has been commissioned by authorized per-sonnel and the external power isolators are closed.Before startup, disconnect the load.

Start the UPS modules separately and set theparameters of each UPS module through configura-tion software. Pay particular attention to the param-eters directly relevant to the parallel system:

UPS Configuration: Each UPS module belongingto the parallel system should be set asParallel

configuration. UPS ID No.: Each UPS module should have a

unique identification number in the parallel system.

Parallel system requisite UPS units: Set the mini-mum number of UPS modules to support theusers expected load. For 1+1 systems this settingsneeds to be set to 1.

Parallel system redundant UPS units: Set theredundant number of UPS modules which will notcause the parallel system transfer to bypass even

NOTE

The length and specifications of powercables including the bypass input cablesand UPS output cables should be the same,thus the load can be shared evenly inbypass mode.

!CAUTIONThe operations in this section must beperformed by authorized electricians orqualified technical personnel. If you haveany difficulties, contact Liebert GlobalServices at 800-543-2378.

#1 UPS Module #2 UPS Module

Parallel Board Parallel BoardX5

X4

X2-2X2-1X2-2X2-1

X4

X1-1 X1-1X1-2 X1-2

1 2

4

3

Interconnecting Cables

1 2

Parallel Connection Board

UPS Unit

4

3


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Liebert Corporation1050 Dearborn Drive

P.O. Box 29186

Columbus, OH 43229

Telephone: 1-800-877-9222

Facsimile: 1-614-841-6022

www.liebert.com

2004 Liebert Corporation

All rights reserved throughout the world. Specifications sub-ject to change without notice.

Liebert and the Liebert logo are registered trademarks ofLiebert Corporation. All names referred to are trademarks orregistered trademarks of their respective owners.

SL-25246 (10/04) Rev. 0

if they get failure during operation. For 1+1 sys-tems, this settings needs to be set to 1.

System Startup

1. Start each UPS normally as described in LiebertNX installation manual. SL-25215.

2. Turn on the inverter of each UPS module one at atime.

3. Apply the load after the last UPS module transfersto inverter. The total load can be determinedthrough the LCD of either UPS.

4. Verify the load rate of each UPS module. If theload rates are roughly the same, then the parallelsystem may be assumed to be operating normally.

Emergency Power Off (EPO)

The external emergency stop facility is identical tothat described for the single unit installation thatan individual emergency stop button is provided foreach unit. Note that this is a Normally Openswitch.

Figure 3 Connecting EPO push button

NOTE

The settings should be the same for allmodules within the parallel system, exceptthe UPS ID No.

NOTE

If one module cannot transfer to invertermode long after its inverter is on, its outputconnection may not be good or its outputphase rotation may not be coincident withother modules. At this time, the LCD for theUPS module will display inverterasynchronous and the inverter indicator

will flash continuously. If either UPSmodule makes abnormal noise after ittransfers to inverter, its parallel cables maybe incorrectly connected.

EPO-H

EPO

Monitor board

EPO-L

X2

UPS1

UPS2

EPO-HMonitor board

EPO-L

X2

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