Design And Construction Of An Automatic Three Phase Power Changeover Control System With 8Kw Voltage Regulator

ABSTRACT

In this research, a “3-Phase Automatic Power Change Over switch” has been designed and implemented using three voltage Comparators (LM741), two BC 108 transistors and 12V, 30mA relay as well as some biasing resistors. The voltage Comparators (LM741) were biased to sense the unregulated voltage – one for each of the three phases (Rø, Yø, Bø) and then couple the analogue outputs to the 3-input-AND gate (4073). The output of the gate when coupled to the base of switching transistors (BC 108) determines their states (OFF or ON). Since the transistors are configured in a Darlington pair arrangement, the second is ON only when the first is OFF. This then triggers the public power supply ON due to normal phase voltage. On the contrary, when the first transistor is ON, the 12V battery produces a potential which triggers ON the alternative power source (Generator) via the 12V, 30mA relays hence breaking contact from the public power supply to the Generator side. The switch is tested to have function optimally within ±5% nominal voltage of 220 or 415V supply at the point of changing over to an alternative power source. Hence this device can be of Industrial or domestic use where 3-phase  power supply is available with a stand-by power source.

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• AIM/OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• STATEMENT OF PROBLEMS
• LIMITATION OF THE PROJECT
• PURPOSE OF THE PROJECT
• APPLICATION OF THE PROJECT
• METHODOLOGY
• PROJECT ORGANIZATION

CHAPTER TWO

2.0      LITERATURE REVIEW
2.1      REVIEW OF ELECTRICAL PHASES
2.2     REVIEW OF THREE-PHASE ELECTRIC POWER
2.3     REVIEW OF THREE PHASE GENERATION AND DISTRIBUTION
2.4    REVIEW OF THREE-PHASE LOADS

2.5     OVERVIEW OF RELEVANT TECHNOLOGY

2.6     REVIEW OF RELATED WORKS EXISTING SYSTEM

2.7     SUMMARY OF REVIEWED WORKS

CHAPTER THREE

3.0      METHODOLOGY

3.1      BLOCK DIAGRAM OF THE SYSTEM

3.2      DESCRIPTION OF SOLAR INVERTER UNITS

3.3      SYSTEM CIRCUIT DIAGRAM

3.4     CIRCUIT OPERATION

• THREE PHASE INPUT TO SINGLE PHASE OUTPUT
• VOLTAGE REGULATOR CIRCUIT DIAGRAM
• VOLTAGE REGULATOR CIRCUIT DESCRIPTION
• SYSTEM OPERATION
• DESCRIPTION OF COMPONENTS USED

CHAPTER FOUR

RESULT ANALYSIS

4.0     CONSTRUCTION PROCEDURE AND TESTING

4.1     CASING AND PACKAGING

4.2     ASSEMBLING OF SECTIONS

4.3     TESTING OF SYSTEM OPERATION

4.4      COST ANALYSIS

CHAPTER FIVE

5.0     CONCLUSION

5.1     RECOMMENDATION

5.2     REFERENCES

 CHAPTER ONE

1.0                                             INTRODUCTION

1.1                                     BACKGROUND OF THE PROJECT

Power supply instability in developing countries creates a need for automation of electrical power generation or alternative sources of power to back up the utility supply. This automation becomes necessary as the rate of power outage becomes predominantly high. Most industries and commercial processes are partly dependent on generators and public power supply which is epileptic especially in tropical African countries where Nigeria forms a part. Therefore, if the processes of power change-over between these two power- supplying sources are manual, human error during change-over connections may occur; leading to machine damage, electric shock/electrocution as well as increased down time consequently introducing massive losses [1].

An Engineering Author, “Tony Rudkin” said in his book titled “Upgraded Signal Source with Improved Performance and Reliability” that the cost and depredation associated with breakdown vary from one application to the other, and in some cases, the user has little choice but to ensure that a stand-by unit is available to take over on event of failure of primary system.

If some of these big firm do not make provisions for stand-by power source, frustration could set in which may lead to the closure of business and thus throwing workers into unemployment. Also in the case of hospital, undergoing a surgical operation and power supply suddenly go off, the patient might loose his or her life due to the power outage.

Furthermore, if the president of the country is making nationwide broadcast and all of a sudden power went off in the transmitting station, it would be viewed as an attempt to sabotage the government ruling and some people must pay for it.

In his book, Tony Rudkin also said that the depredation caused by such reduce efficiency of the organization and leads to a great deal of frustration.

Sequel to the rate at which more sophisticated electrical/electronics gadgets are being procured and installed in our homes, hospitals and business premises, there is a justifiable need for a faster and more reliable change over system in an event of power outage.

The Changeover system switches off a power supply and subsequently switch on another power supply. Basically it is aimed at switching on a more convenient power supply to the load.

Since it switches on power to the load, precautions has to be taken while choosing the type of Change over Switch, while selecting the appropriate size, the control of arcing has to be put into consideration.

A good switch should be the one whose contact is made in such a way as to limit the arc formation by having no contact-bounce and by having contacts made of good conductive, corrosion resistance and wear resistance materials.

A good change over switch must have adequate insulation and must be so constructed and located as not to constitute a potential hazard.

A good change over switch should also have tight contact points so as to limit or eliminate the possibility of partial contact at the contact point. The partial contact leads to overheating of the components and may lead to fire outbreak in the entire room.

1.2                                   PROBLEM STATEMENT

Power outage, over-or-under voltage in a country, state or city is highly detrimental to development in public and private industries. The insecurity associated with constant or frequent power failure or outage brings about limitation to power consistent investments, thus hampering the development of industries and multinational ventures. Processes like carrying out surgical operations in hospitals, laboratories which require constant and stabilized power supply for research, money transactions between banks and more require constant use of uninterrupted power. In other to solve this problem, an automatic changeover switch was invented. This research covers the design and construction of a single phase digital automatic power changeover. It has the capacity to automatically switch power from  national grid to generator and vice versa, once there is power failure in any of the two power supplies and at the same time has the capacity of shutting down a generator set once the mains grid is been restored.

1.4                               PURPOSE OF THE PROJECT

The main purpose of this work is to provide a means of having uninterruptible and regulated power supply in our home, office, workshops or industries.

1.5                            OBJECTIVE OF THE PROJECT

The objective of this work is to design a device that will overcome power interruption, under-voltage and over-voltage supply by automatically regulating and switching power from national grid to generator and vice versa

1.6                                      SIGNIFICANCE OF THE PROJECT

Industries require three phases power to run their machineries. Some of them require continuous \ uninterrupted power to maintain their data.

Auto three phase power changeover introduces an automatic solution to overcome power interruption by automatically switching power from  national grid to generator and vice versa

This automatic change over unit operates in three phase system. The automatic change over switch has the following advantages;

It minimizes damages to lives/equipment since it has its own monitoring system and its switching requires no human contact with the switch, thus eliminating human error.

It reduces its change over timing to the minimum due to its fast response to power outage.

It maintains high quality of service through its fast and prompt response.

Moreover, the size and captivity of the unit will depend upon the load for which it will be used. The unit is also portable, easy, convenient and safe to install.

It also regulates input voltage and thereby giving out 220v alternating current.

1.4                         LIMITATION OF THE PROJECT

In the course of designing this project, different kinds of problem was notice such as:

• Difficulty in troubleshooting with circuit without the circuit diagram
• Difficulty in connecting the output without the three phases short-circuiting, until a multiplexing circuit was gotten.
• Difficult in wiring because of the strong wiring the project required.
• This automatic change over unit operates in three phase system.

1.5                                 SCOPE OF THE STUDY

This work covers only a three phase automatic changeover which can only be used for providing a means of switching from generator to utility supply in the case of failure in the three-phase and at the same time provide a regulated voltage output.

1.6                           APPLICATION OF THE PROJECT

This device is used in the following places:

1. home,
2. office,
3. worship places
4. workshops or industries

1.7                                         METHODOLOGY

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.

• Test for continuity of components and devices,

1. Design and calculation for the changeover was carried out.
2. Studying of various component used in circuit.
3. Construct a digital changeover circuit.

• Finally, the whole device was cased and final test was carried out.

1.8                                             DEFINITION OF TERMS

POWER OUTAGE / POWER FAILURE: A power outage is the loss of the electrical power network supply to an end user.

AUTOMATIC CHANGEOVER is device that automatically transfers power from generator supply to PHCN supply when available and stops the generator without without human intervention

1.8                                             PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied,  chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.