Chapter 4 System Description; Brief Introduction; Operating Theory; Static (Bypass) Transfer Switch - Emerson NXr User Manual

30kva ~ 200kva

Table of Contents

Chapter 4 Operation

This chapter introduces the information related to UPS operation, including the brief introduction, 1+N parallel system,

operation mode, battery management and battery protection.

No user-serviceable parts are located behind covers that require a tool for their removal. Only qualified service personnel are

authorised to remove such covers.

4.1 Brief Introduction

The UPS provides continuous, high-quality AC power to your critical equipment, such as telecommunications and

data processing equipment. The UPS supplies power that is free of the disturbances and variations in voltage and

frequency common to mains power, which is subject to brownouts, blackouts, surges and sags.

The UPS uses the latest high frequency, double-conversion pulse width modulation (PWM technology and digital

signal processing (DSP technology to enhance its reliability and increase the ease of use.

4.1.1 Operating Theory

As shown in Figure 4-1, the AC mains source is converted by the rectifier into DC power. The inverter converts that

DC power from the rectifier or the DC power from the battery into AC power, and provides the AC power to the load.

The battery supplies the load through the inverter in the event of a mains failure. The mains source can also supply

the load through the static bypass.

If UPS maintenance or repair is necessary, the load can be transferred without power interruption to the maintenance

bypass.

4.1.2 Static (bypass) Transfer Switch

The circuit block labeled STS (static transfer switch) in Figure 4-1 contains an electronically controlled switching

circuit that enables the load to be connected to either the inverter output or to the bypass power source through the

static bypass line. During normal system operation, the load is connected to the inverter; but in the event of a UPS

overload or inverter fault, the load is automatically transferred to the static bypass line.

During normal operating conditions, the inverter output and bypass supply must be fully synchronized so as to

achieve a clean (no-break) load transfer between the inverter output and static bypass line. The synchronization

between the inverter output and static bypass is achieved through the inverter control electronics, which make the

NXr UPS Module And Parallel System 30kVA ~ 200kVA User Manual