Design And Construction Of A 4Kva Uninterruptible Power Supply

ABSTRACT

The purpose of this project is to design and construct an uninterruptible power supply. Uninterruptible power supply is an uninterruptible power device planned to electromechanically sustain a power supply. 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. This project is aimed at building a uninterruptible power supply of 4kva.

TABLE OF CONTENT

COVER PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• PROBLEM STATEMENT
• AIM OF THIS PROJECT
• OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• THE SCOPE OF THE PROJECT
• LIMITATION OF THE PROJECT
• DEFINITION OF TERMS

CHAPTER TWO

2.0     LITERATURE REVIEW
DESCRIPTION OF UNINTERRUPTIBLE POWER SUPPLY

2.1     HISTORY OF UPS

2.2     THE POWER SUPPLY

2.3      THEORY OF TRANSFORMER

2.4     OPERATION OF THE TRANSFORMER

2.5     VOLTAGE TRANSFORMER RATION (K)

2.6      TRANSFORMER LOSSES

2.7      REVIEW OF MAJOR COMPONENTS USED RELAY

2.8     REVIEW OF AN AUTO-TRANSFORMER AND ITS OPERATION

CHAPTER THREE

CONSTRUCTION METHODOLOGY

3.0     SYSTEM BLOCK DIAGRAM

3.1     UPS USING MICROCONTROLLER CIRCUITS

3.2     CIRCUIT DESCRIPTION AND OPERATION

3.3     CIRCUIT DESCRIPTION AND OPERATION

CHAPTER FOUR

RESULT ANALYSIS

4.0     CONSTRUCTION PROCEDURE AND TESTING

• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION
• COST ANALYSIS
• PRECAUTIONS

CHAPTER FIVE

5.1CONCLUSION

5.2     RECOMMENDATIONS

5.3      REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

In this modern society, electricity has great control over the most daily activities for instance in domestic and industrial utilization of electric power for operations. Electricity can be generated from public supply to consumers in different ways including the use of water, wind or steam energy to drive the turbine as well as more recently the use of gas. Generators, solar energy and nuclear energy are also source of electricity.

It is designed to meet up with the AC voltage safety, stability and accuracy demand in industries and in homes. Uninterruptible power supply is useful in devices such as computer Power supplies, alternators and central power station generator plants, voltage regulators control the output of the plant.

An uninterruptible power supply automatically maintain a constant AC voltage level. An AC Voltage supply may be a simple “feed-forward” design or may include negative feedback control loops. It makes use an electromechanical mechanism, and other electronic components.

The general objective of the system is to provide efficiency in the use of power supplies by ensuring continuous availability of power supply in the absence of mains supply. Uninterruptable capacity of the system made it possible to eliminate all suspense arising from national gird 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.

1.1                        BACKGROUND OF THE STUDY

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, the 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 PHCN and hence obtaining a PHCN 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                                              PROBLEM STATEMENT

If there is one factor that has perpetually maintained the status of Nigeria as a less developed country, it is its power sector. Till date, many households and industrial businesses cannot be guaranteed of 24 hours supply of electricity from the National grid. At this stage of Nigeria’s social and economic development, the country cannot deliver sufficient energy to the citizens despite huge financial resources that have been expended in the sector.

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 was invented to overcome these challenges by providing its equipment with two source of power.

1.3                                               AIM OF THIS PROJECT

The main aim of this work is to build a device that sustains an AC output voltage of 240V with a backup power source which provide additional power to the device during mains power outage automatically at 50Hz using a 12v battery.

1.4                                          OBJECTIVE OF THE PROJECT

The objectives are:

• To avoid noise in the surrounding which is produced by gasoline engines such as diesel and petro generators.
• To save cost of fueling and maintenance of gasoline engine generators.
• To reduce damage of electronic appliances as a result of unstable power supply.
• To ensure that, there is continuous power supply.
• To generate 220V AC output from a 12V DC source.

1.5                                      SIGNIFICANCE OF THE PROJECT

Working on this work as a student of this institution will serve as a means of learning how to build electronics gadgets. This work will serve a manual for a sustainable power supply.

Finally, this work will serve as an eye opener to every reader: it will expose readers to the operating principle and wiring of electronics devices such as relay, comparator and transformer.

1.6                                         THE SCOPE OF THE PROJECT

The scope of this work covers building a device whose function is to maintain constant and uninterruptible power to electrical appliances. 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.

1.7                                        LIMITATION OF THE PROJECT

The system design shall be capable of operating at an input frequency range of -15% to +10% of nominal, without clearing protective devices or causing component failure within the uninterruptible power supply. During mains power outage the system shall be working with inverter source section, but when generator or utility power is restored, the uninterruptible power supply shall automatically restart. Upon turn on or restart, the output of the uninterruptible power supply shall not exceed the specified output regulation limits.

Response Time: The uninterruptible power supply shall respond to any line voltage variation in 1/2 cycle while operating linear or non-linear loads, with a load power factor of 0.60 of unity. Peak detection of the voltage sine wave shall not be permitted to avoid inaccurate tap switching due to input voltage distortion.

Operating Frequency: The operating frequency of the ups is 50Hz.

Rating: this device is rated at 4KVA.

Access Requirements: The uninterruptible power supply shall have removable panels on the front, rear and sides as required for ease of maintenance and/or repair.

Metering: An input meter is provided to reading line voltages

Ventilation: The uninterruptible power supply isolation transformer shall be designed for convection cooling. A fan cooling is required for the solid state electronic switching devices.

1.8                                                  DEFINITION OF TERMS

(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.