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Title Page



Table of Contents

Chapter One

1.0     Introduction

1.1     Background

1.2     Aims

1.3     Scope

1.4     Definition

Chapter Two

Complete Circuit Description

2.0     Simplified block diagram of thee 3-way intercom system

2.1     Operation Principles

2.2     Conversion

2.3     Inversion

2.4     Power Source

2.5     Oscillator

Chapter Three

3.0     Construction

3.1     Circuit Diagram

3.2     Component and Key Symbol

3.3     Sequence of Operation

3.4     Testing and Result




Chapter Four

4.0     Observation

4.1     Summary

4.2     Suggestion

4.3     Explanation of the Switching Circuit

4.4     Conclusion

4.5     Reference










The idea behind a UPS (Uninterruptible Power Supply) is pretty obvious from the name, in addition to filtering, enhancing or modifying the unity power, special circuit and batteries are used to prevent electrical machines from losing power during a disruption (blackout or voltage sag brownout). The units are all called different names depending on the next design, but all fit into general category of backup power.

Before delving into details of how an uninterruptible power supply works, let’s take a quick look of the basic of the type of equipment. An electrical device plugged into the wall or into a surge suppressor has only one source of power. If there is a blackout, the electricity is out an the device obviously goes off immediately. A UPS changes this equation by providing its equipment two source of power.

UPS are designed so that there is one source of power normally used called the primary power source and another source that kicks in if the primary is disrupted called the secondary power source. The power from the wall is always one of those sources and the battery contains within the UPS is the other. A switch is used to control each of these powers and the equipment of any given time. The switch changes from the primary of the secondary when it detects the primary has gone out. It switches back from the secondary power the primary power, source has returned.

Contrary to what you might think, the wall A.C power is not always the primary power source and the battery the secondary source. Which source is primary and which is secondary depends on the type of UPS. Therefore, circuit is provided with this UPS to convert AC power to DC to change the battery. A device called an invert is also provided to change the battery stone DC electricity to AC to run your equipment.

Furthermore, those components of the uninterruptible power supply and other one discussed in details in the section covering the various parts of the UPS. The size of the UPS is primary dictated by the size of the time your equipment can run on battery power switching down, higher units not only can power equipment for more time they can also handle a large total demand for power.




In this section we will take a brief look of the various parts that are made up of typical UPS. Focus is on small units more commonly used for home and smaller business.

INVERTER PART: That is inversion circuit, all UPS include cone circuit that manipulates electricity converting it from AC power produced by your utility company to DC power stored in the battery and back again for use by your equipment. The inverter section converts a DC voltage into an AC voltage with the help of an oscillator. This section also consists of two stages of switching circuits which comprises of a power transistor connected i in the common emitter configuration.

Since the oscillator has two outputs each of the switching circuits is coupled to the two outputs of the oscillator respectively. The two outputs one explained in detail in subsequent chapter. The exact type, netune size and quality of the circuit depend on the type of UPS and more specifically the model you have chosen. As with all things the better the unit, the high the quality of the components and as with all thins quality is often corrected to price but not always.

Voltage conversion and inversion, the process of changing AC to DC is called conversion (actually, this is an imprecise term because conversion refers to changing our DC voltage to another and other thing as well, but it will do for our purpose device that perform this process are called converters, but are also sometimes called adapter, and if being used for changing batteries they are often just called charger. Charging DC into AC is the opposite process and is called inversion. A device that does this is of cause called an inverter.

The Automatic control unit, this unit provides all the required control needed to meet up the aim of the entire system. Controls like automatically “ON” of the system into NEPA and hence obtaining a NEPA line jamming is encountered by properly carrying out the exchange system.

Meanwhile, in bringing background information it is important to have a look of the block diagram of a complete UPS. A very basic block diagram of a UPS, showing basic design of to power sources, controlled by a switch is drawn above.



1.2    AIMS

The general objective of the system is to provide efficiency in the use of power suppliances by ensuring continuous availability of power supply in the absence of NEPA. Uninterruptability of the system made it possible to eliminate all suspense arising from NEPA outage during the execution of an important and urgent assignment requiring

The use of power especially with computer PC system. The fundamentals purpose of a UPS is to provide an interrupted source of power for the equipment it protects.

For better production of the system it is advisable to operate the system of a fully charged condition of the battery. Also the problem due to excessive heating could be eliminated by the use of a hat sink with a thick and a large surface area for sufficient absorption of heat. This project is rated 200W of 220V and 50H2. It is expected at all condition favourable to carry load of higher power factor of the approximation of the power stated. Loads of low power factor are always not helpful overloading is not potent to provide zero changeover time and has audio helper which indicates mains fail and battery discharge. It provides 100% protection against live noise, swages all radio frequency interference.

1.3              SCOPE

A UPS makes it possible to provide a clean reliable supply of alternating current free of says or surges in the line voltage frequency variation, spikes and transient. UPS systems achieves this by rectifying the standard mean supply, using the direct current to charge the standby battery and to produce clean alternating current by passing through an inverter and filter system. It has zero change over time and has audio beeper which indicates mains foil and battery discharge. It provides 100% protection against line noise spikes surges and audio frequency interference.


(i)      Inverter Unit:      This unit converts a DC voltage into an AC voltage with the help of a oscillator.

(ii)    Automatic Control Unit:        This provides all the required control needed to meet up the objectives of the whole system.

(iii)    Battery Unit:       This is a secondary cell unit capable of storing enough DC voltage of which is later converted to AC voltage.


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