Liebert 300 User Manual

DISCONTINUED

PRODUCT

OPERATOR’S
MANUAL

POWER PROTECTION

Series 300

Three Phase
Uninterruptible
Power System

WARNING

READ BEFORE

HANDLING

OR INSTALLING.

ONLY QUALIFIED

PERSONNEL
SHOULD HANDLE
THIS EQUIPMENT.

Load Bus
Synchronization
Option

Table of Contents

Section 1 Introduction

1.0 System Description ................................................................................................ 1

Section 2 Theory of Operation

2.1 General Description................................................................................................ 2

2.2 Load Bus Sync Controller ..................................................................................... 2

2.3 Series 300 LBS Module Interface .......................................................................... 2

2.4 System Operation .................................................................................................. 3

Section 3 Operation

3.1 Operator Controls .................................................................................................. 4

3.2 Operator Procedures .............................................................................................. 5

Series 300 Load Bus Synchronization

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SECTION 1 INTRODUCTION

1.0 SYSTEM DESCRIPTION

The Liebert Load Bus Sync™ (LBS) option keeps the output of two independent Uninterruptible
Power Systems (UPSs) in sync, even when the two UPSs are operating from two different power
sources. Any UPS will typically sync to its own bypass source. As long as both UPSs are tied to the
same input and bypass sources, they will automatically stay in sync. However, if the UPSs are
operating on batteries, or different backup generators, or asynchronous bypass sources, their outputs
will tend to drift out of sync.

Maintaining sync is critically important for installations with dual power distribution systems. These
sites typically feature Liebert Precision Power Centers (PPC) with Liebert Static Bus Transfer
Switches. Each PPC has dual inputs: it can receive power from either UPS, and switch seamlessly
between the two as long as the UPS outputs are held in close synchronization. This provides
redundancy down to the PPC level. It also permits one entire half of the distribution system (upstream
of the PPC) to be taken offline for maintenance or repairs.

The Load Bus Sync option consists of an LBS interface in each UPS module plus one LBS controller
enclosure installed between the UPSs.

Figure 1. LBS Controller Enclosure

Series 300 Load Bus Synchronization 1

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