Chapter 1 - General Description; Introduction; Design Concept; 7200 Module Design - Liebert 7200 Series User Manual

7200 Series UPS User Manual
Single Module and 1+1 Parallel System
1.

Chapter 1 - General Description

1.1

Introduction

The 7200 Series uninterruptible power supply (UPS) system is connected between a critical load, such
as a computer, and its three phase mains power supply. Being designed to furnish a well regulated 3
phase output power supply under all rated load and input supply conditions, the system offers the user
the following advantages:
Increased power quality:
The UPS has its own internal voltage and frequency regulators which ensure that its output is
maintained within close tolerances independent of voltage and frequency variations on the mains power
lines.
Increased noise rejection:
By rectifying the input a.c. power to d.c. power, and then converting it back to a.c., any electrical noise
present on the input mains supply line is effectively isolated from the UPS output, therefore the critical
load sees only clean power.
Power blackout protection:
If the mains power fails, the UPS continues to power the critical load from its battery source, leaving
the load immune from power disturbances.
1.2

Design Concept

1.2.1

7200 Module Design

Bypass
a.c.
Supply
RECTIFIER
Rectifier
a.c.
Supply
This section describes an individual module's operating principles. The UPS basically operates as an
a.c.-d.c.-a.c. converter (see figure 1-1). The first conversion stage (from a.c. to d.c.) uses a 3 phase,
fully-controlled SCR bridge rectifier to convert the incoming mains supply into a regulated d.c. bus-
bar.
The d.c. bus-bar produced by the rectifier provides both battery charging power - which uses a
temperature compensated battery charging system, to prolong battery life - and power to the inverter
section – which utilizes the latest IGBT switching pulse width modulation ( PWM ) design - and
provides the second conversion phase, i.e. reconverting the d.c. bus-bar voltage back into an a.c.
voltage waveform.
document in response to "powersure ups"
INVERTER
BATTERY
Figure 1-A . Single Module block diagram
STATIC
SWITCH
and K1
UPS
a.c.
Output
Chapter 1 - General Description
Design Concept
Page 1-1
Issue 6
(03/98)