(Electrical Engineering)



This is a technical report presented on the design and construction of an Automatic Three Phase Selector.

        In the construction work, an ordinary level knowledge of electronics principles are observed. We aimed at presenting a practical aspect of the subject and then providing the argument necessary for a thorough understanding. The reliability of the specimen was estimated after construction and testing to ensure steady state stability. The work is organized into five chapters.

        Chapter one introduced the subject matter. Chapter two explores the literature review of the related works. Chapter three contains a detailed account of the design work while chapter four closely attempted an analysis of the design work. Chapter five draws the curtain by concluding the work.



1.0        Introduction

1.1        Aims/Objectives of the project

1.2         Significance of the study

1.3        Methodology


2.1 A review of Automatic Phase Selector

2.2 Power Supply Unit

2.3 The Transformer

2.4 The Rectifier

2.5 The Filter

2.6 The Voltage Regulator

2.7 Power Circuit

2.8 The Relays


3.0 The Design Proper

3.1 The Power Supply

3.2 The Step down Block

3.3 The Rectifier Block

3.4 The smoothening Block

3.5 The Regulator

3.6 The Current Sink


4.0 Design Analysis

4.1        The Rectifier Circuit

4.2        The Filter Circuit

4.3        Design Calculation

4.4        The DC Voltage Regulator

4.5        The Voltage Programmable Voltage Sink


5.0 Discussion of Result

5.1    Conclusion

5.2    Recommendation




As the growing population of human race widens the gulf between energy supply and energy demand, the imbalance in energy availability sent researchers into excavating for a way of settling this age long squabble. A lasting solution is vested on alternative use of the renewable energy source, a project that is yet to be widely applied. Hence, the continuation of the unsettled yearn for sufficient power. Consequently, the power lines are frequently over loaded resulting to a trip of power by the action of switch gears or by the load shading process undertaken by the distribution authorities.

        Since it is crystal clear that some institutions such as health related institutions and some other delicate systems should not be allowed to suffer equally with their counterparts, Automatic Phase Selector is used to sustain energy consumption in the time of phase trip. The design of this circuit involves the use of automatic switches but the details of design varies from place to place, time to time and also depends on the type of load involved.

        This project involves the use of transistor driven relays to affect the change of phase whenever the voltage condition becomes intolerable in the previous phase connected.  



The analysis of this project cannot go without enumerating the goals meant to be achieved in the pursuit of the work. These objectives include:-

i.        To develop a simple low cost device aimed at easing the prevalent burden faced by delicate offices, parastatals and institutions who need very low but constant power supply. Since supply is always on along the distribution lines that supply such sites, what pesters on the progress of work thereof is always the unwarranted trip of phases due to power usage from neighbouring consumers. The automatic phase selector therefore, erase this setback form the face of progress of work in such offices.

ii.      To stimulate the interest of upcoming students to take up research not only in their field of study “Electrical/Electronics Engineering” but also to extend their arms to other disciplines, thus enhancing the versatility of Electrical/Electronics Engineering.

iii.    To create awareness that will stimulate the interest of fellow students who intend to take up research topic on automatic switch of any type.


    Emphatically, the purpose of this project is to build an automatic switch system which is capable of selecting a phase with best operating voltage for delicate offices.


The significance of this project work cannot be overemphasized. This is because the number of lives that has being lost to the hand of interruption of power in health institutions and the like is not negligible. Delicate appliances have become the main victim of this artificial circumstance. The applicability of the outcome of this research work in several facets of human endeavour makes this work of real importance to humanity.

        The use of the device produced from this research work would help to reduce human labour and hazard, going by the fact that many have been handicapped by electric shock because of the attempt they made to select another phase, and that the handicapped are helpless and cannot change phases.

1.3          METHODOLOGY

The designing of this circuit was accomplished by a constant and detailed study of the c constituent components. This involved the study of their  characteristics in isolation, and when connected together with some other components. A rough design was always made with some theoretical backup. Those designs were implemented and tested using project boards.

        The internet was visited for circuit ideas where problems were encountered and the necessary adjustments made on paper and then effected on the projects board.

        Each block that works was transferred to the Vero board where it was finally soldered in position. Library materials were consulted as well.


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