7400 Series UPS User Manual Chapter 1 - General Description
Single Module and One plus One Systems Introduction
6310018a.02.doc
1-1
Issue 2
(02/98)
1. Chapter 1 - General Description
1.1 Introduction
The 7400 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 regulator circuits
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
This section describes an individual module’s operating principles for
both 6 and 12 pulse systems - the effects of the additional parallel control
facilities required on the one plus one system on the standard module are
described later.
6 pulse Rectifier
The UPS basically operates as an AC-DC-AC 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 446 V d.c. busbar for a 400 V a.c. input (or 432 V d.c.
for a 380 V a.c. input or 459 Vd.c. for a 415V a.c. input).
1.2.1 Module Design
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