Emerson 7400 user manual Redundant vs Non-Redundant configuration, Introduction

Series 7400 Single Phase 1+N UPS

Chapter 1

General Description

1.1 Introduction

The Uninterruptible Power Supply system is connected between a critical load, such as digital drives & automation, distributed digital Process Control System, telecom equipment, programmable logic controller, mission critical applications, computer, and its three phase mains power supply. Being designed to furnish a well regulated 1 PH output power supply under all rated load and input supply conditions the system offers the users 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 AC power to DC power, and then converting it back to AC, 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 Concepts

1.2.1Redundant vs Non-Redundant configuration

The one-plus-onesystem comprises two standard 7400 series UPS modules which are modified to allow their outputs to be connected in parallel. These can then be used in a “redundant” or “non- redundant” configuration as explained below.

In a non-redundant module configuration, the system is sized such that both UPS modules are required to feed the potential load, and if one of the two modules develops a fault, or is for some reason shut down, the other module automatically shuts down also.

Note: In such an event the load is transferred to an unprocessed bypass supply - as described later.

In a redundant module configuration the system is sized such that the potential load can be provided by just one of the two modules. Under normal circumstances both modules are operational and share the load current equally; but if one module develops a fault, or is shut down, the second module is able to take over the full load demand and continue to provide it with processed, backed-up power. The advantages of a redundant system over a non- redundant system in terms of overall system reliability are self- evident.

Changing a one-plus-onesystem’s configuration between redundant and non-redundant is quite straightforward, being carried out by configuration links on the circuit board, which governs the modules’ parallel control operation.

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