Design And Construction Of A 3.5Kva Uninterruptible Power Supply

ABSTRACT

The purpose of this project is to design and construct an uninterruptible power supply. Uninterruptible power supply is a voltage regulatory and uninterruptible power device planned to electromechanically sustain a constant voltage level and supply an uninterruptible power to devices.

This device receive minimum voltage of 120vac and maximum of 260vac and filter the current and voltage thereby brings out suitable voltage output to be used by the devices in it, then when there an unexpected power outage from the utility mains or generator the system will automatically switch over to the inverter source thereby providing additional power to the appliances in use without interruption.

This device stabilizes an AC input voltage of 120-260V to give an AC output voltage of 240V, provide a rechargeable backup power supply the system and also provide low battery indication automatically. The automatic feature can be achieved by the electronics devices used such SG3524N IC, electro-magnetic device (relay), auto- transformer and other electronics devices.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• STATEMENT OF THE PROBLEM
• PURPOSE OF THE PROJECT
• AIM AND OBJECTIVES OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• SCOPE OF THE PROJECT
• LIMITATION OF THE PROJECT
• DEFINITION OF THE PROJECT
• METHODOLOGY
• PROJECT ORGANIZATION

CHAPTER TWO

LITERATURE REVIEW

• DESCRITION OF UNTERUPTIBLE POWER SUPPLY
• HISTORICAL BACKGROUND OF UPS
• THE POWER SUPPLY
• THEORY OF TRANSFORMER
• OPERATION OF THE TRANSFORMER
• VOLTAGE TRANSFORMER RATION (K)
• TRANSFORMER LOSSES

CHAPTER THREE

METHODOLOGY

• SYSTEM BLOCK DIAGRAM
• SYSTEM CIRCUIT DIAGRAM
• SYSTEM OPERATION
  • The oscillator stage
  • Power drive stage for pwm ups circuit with charger
  • Battery charging section
• DESCRIPTION OF COMPONENTS USED

CHAPTER FOUR

4.0      TEST AND RESULT ANALYSIS

• CONSTRUCTION PROCEDURE AND TESTING
• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION
• COST ANALYSIS
• PROBLEM ENCOUNTERED
• PRECAUSION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

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.

In Nigeria and some other parts of the world today, the electricity power supply to consumers (at homes and industries) is not maintained at a stipulated voltage say 240 volts.  But the electronic gadgets and some other power operated machines, that we use in our homes, offices and industries requires power with constant and interruptible  for their efficiency, and to avoid damage by the voltage. In Nigeria, there is inconsistence supply of electricity by the power supplying company to the consumers.  The use of additional electric power source such as electric power generators and most recently the use of semiconductor power devices such as the Bipolar Transistor, Thyristors and particularly MOSFET to generate electric power in conjunction with a DC battery in few kilowatts. An Inverter offers a better additional power source to Generators as well as UPS considering its long duration, cost effectiveness and maintainability.

Uninterruptible Voltage supply is an electronic control circuit or device that is capable of providing a constant output voltage even when there is variation in load or input voltage as low as 160 volt can be boost up to 240 volt by stabilizer at output stage without any voltage fluctuation with a backup battery which provide additional power to the device during mains power outage.

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. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line.

An uninterruptible power supply is designed to automatically maintain a constant AC voltage level. An AC Voltage supply may be a simple “feed-forward” design or may include negative feedbackcontrol loops. It makes use an electromechanical mechanism, and other electronic components. Depending on the design, it may be used to regulate one or more AC voltages.

This project is designed to stabilize an AC input voltage of 160-250V to give an AC output voltage of 240V at 50Hz automatically. The automatic feature can be achieved by the electronics devices used such voltage comparator IC, electro-magnetic device (relay), auto- transformer and other electronics devices

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, and to maintain a certain voltage supply to a load even when the voltage or frequency of the supply varies.

1.3                                          PURPOSE OF THIS PROJECT

The purpose of this project is to design and construct an uninterruptible power supply. This device stabilizes an AC input voltage of 160-260V to give 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. The automatic feature can be achieved by the electronics devices used such voltage comparator IC, electro-magnetic device (relay), auto- transformer and other electronics devices.

1.4                               AIM AND OBJECTIVES OF THE PROJECT

The aim of this work is to construct a device whose function is to maintain constant and uninterruptible power to electrical appliances, and power line conditioning to the equipment load of 3500w under a wide variety of conditions, even when the utility input voltage, frequency or system load vary widely and also indicate when the battery of the system gets low. The objectives of the study are:

1. To build the system prototype.
2. To provide backup power to our appliances.

• To protect equipment from damage in the event of grid power failure.

1. To provide backup power when your regular power source fails or voltage drops to an unacceptable level.
2. To provide a means of allowing a safe, orderly shutdown of a connected equipment such as computer.

1.5                                      SIGNIFICANCE OF THE PROJECT

The uninterruptible power supply is a voltage regulator planned to mechanically sustain a constant voltage level and supply an uninterruptible power to devices. It can also use electromechanical components. It can be used majorly to regulate one or more DC or AC depending on the design. Therefore, the functions of this equipment are very wide and can be used majorly for various purposes. Electronic voltage regulators can be used majorly for various purposes. It has various functions like it can be used mainly for stabilizing the DC voltages that can be used by the processor and its main parts. In central power station generator plants and automobile alternators, voltage regulators control the output of the plant. In this distribution system, it may be installed at along distribution lines so that all clients recognize steady voltage self-regulating of how much power is drawn from the line. There are many functions of operating the AC depending upon the design. It is very good option to maintain the constant voltage level. Automatic voltage regulator is a superb invention of science, which is an electric device designed to authorize a constant voltage in a settable level. It is very helpful to maintain the preferred voltage for the generators within particular limits. The main working of it depends upon the laws of electromechanical physics. It consists of numerous vigorous and unreceptive electrical parts like thermostats, adopters and diodes. Apart from this, there are many reliable Automotive Suppliers in India that produce many kinds of equipment like generator, regulator and other major parts. They are well known for various kinds of functions and various specifications. They not only produce higher quality products, but also they will provide some additional benefits with the parts of these equipment. Auto Voltage Regulator Generator is the most important part for great amplifier to work. Its types are many, but they are highly in functionality and better performance. They are well equipped with self-functioning controls and starts up functions which make them very easy and useful to handle easily and completely. They have different sizes, shapes and colors. There are also automatic regulators which are so small that they can be easily places on a small printed circuit board. They are very easy and portable to handle. They may cover a higher volume of small house sometimes. Therefore, there is a wide variety in the uninterruptible power supply sand each has its own specifications.

1.6                                              SCOPE OF THE PROJECT

The design and construction of an uninterruptible power supply is the project we are construction.  I am working on this machine because we have some idea on how this machine can be constructed and also on how it works.  We are also doing this because we want to learn more about it.

As we have mentioned earlier, this device is a protective device that protects our electrical and electronic appliances out of current and voltage fluctuation and unexpected power interruption. This is how it works.  When this system is plugged into the socket or supply, it will receive a minimum voltage of 120vac and filter the current and voltage thereby brings out suitable voltage output to be used by the devices in it, then when there an unexpected power outage from the utility mains the system will automatically switch over to the inverter source thereby providing additional power to the appliances in use.

This device was built to reduce risk and damages the fluctuation of current / voltage caused by power fluctuations and unexpected power interruption and the device is rated 3500W.

An uninterruptible power stabilizer consists of an all copper, multiple tapped, contain independently controlled inverse parallel electronic switches for each of the 7 taps per phase to provide tight voltage regulation, rechargeable battery and an inverter. The phase current shall be monitored for zero current recognition to initiate any required tap change. Linear devices shall be used for line synchronization to prevent phase shift errors normally associated with zero current crossing acquisition.

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 uninterruptible power stabilizer shall be capable of operating at +10% to -15% of the nominal frequency, 50Hz.

Rating: this device is rated at 3500VA.

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

(i)        Inverter Unit:         This unit converts a DC voltage into an AC voltage with the help of a oscillator, the oscillator ic used is SG3524N IC.

(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.

1.9                                                    METHODOLOGY

In building this project, to achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Design and calculation for uninterruptible power supply.

1. Studying of various component of an uninterruptible power supply circuit.
2. Construct an uninterruptible power supply circuit.

1.10                                  PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this works is on the introduction to an automatic voltage regulator. In this chapter, the background, significance, objective, aim, scope, limitation and problem, definition of terms of an automatic voltage regulator were discussed.

Chapter two is on literature review of an automatic voltage regulator. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, discussion, recommendation and references.

CHAPTER FIVE

5.1                                                       CONCLUSION

Uninterruptible power supply have very core importance for control of sensitive devices such as computers, induction machines, medical equipment’s and many other things. Uninterruptible power supply also used in many countries where energy shortage is a main issue. In country like Nigeria, many people use UPS in load shedding timings. In such cases, UPS is used to store energy in batteries when main Power supply is available. Same UPS is used to convert DC energy stored in batteries in AC supply to provide power to AC operating equipment’s of homes during load shedding timings. Mainly devices which have severe effect of change in following parameters above and specified limit connect with uninterruptible power supply.

• Over voltage
• under voltage
• voltage out
• voltage spikes
• frequency fluctuation of 1%
• distortion in voltage wave form.

5.2                                                 RECOMMENDATION

This project is designed to be used in our homes, offices and industries where the need for 24hrs supply is needed. And should be used and maintain by a qualified personnel.