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Product Category: Projects

Product Code: 00001098

No of Pages: 64

No of Chapters: 5

File Format: Microsoft Word

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Auto Phase Selector (ASP) system is used to ensure continuous supply to load in case mains supply is not healthy. This unit is very useful at the site at which main supply is irregular. It may be sometimes very high or sometimes very low voltage. The frequent failure/fluctuations of power affect life of power plant and battery. The objective of the APS is to ensure that there is continued commercial power supplied to the site at all times so as to ensure that the Base Transceiver Station BTS) runs on commercial power until all available phases are either out of electrical tolerance or completely off. This is a microcontroller based unit three and it is used with three phase electrical supply.

Whenever the supply of one or two phases of a three phase electrical line goes off, the ASP system automatically distribute the electrical supply from the active phase to the failed phases. These ensure continues power supply through all the three phases even if only one phase is active.




1.1   Background

1.2   Aims/Objectives of the Project

1.3   Relevance of the Project

1.4   Scope of the Project

1.5   Limitations

1.6   Target Beneficiaries

1.7   Significance of Study

1.8   Achievement of the Construction of the Project




2.1   Introduction

2.2   Effect of Power Failure 

2.3   Equipment Voltage Susceptibility

2.4   System Interactions and Solutions

2.5   Background of the Automatic Three Phase Selector




3.1   Information Gathering 

3.2   Ways of Effecting the Design and Construction of an Automatic three Phase Selector 

3.2.1 Phase Selection by Manual Control

3.2.2 Phase Selection by Sequential Logic Control

3.2.3 Phase Selection by Microprocessor Control

3.2.4 Phase Selection by Comparator Control



4.1   Components Used in the Design and Construction of the Automatic Three-Phase Selector

4.2   The Design Topology  

4.2.1 The Power Supply Block

4.2.4 The Relays Switches

4.3   Design of the Circuit

4.4   Work of LM 741 Comparator

4.5   Comparator Using Operational Amplifier

4.6   Principle of Operation/Circuit Working of the Automatic Three-Phase Selector




5.1   System Testing

5.1.1 Testing Procedures and Results 

5.2     Problems Encountered

5.3     Result

5.4     Conclusion

5.5     Recommendations 





Fig 1: Block diagram showing the various stages of the automatic phase selector.

Fig 2: Block diagram of power supply

Fig 3: Transformer only

Fig 4: Transformer + Rectifier  

Fig 5: Transformer + Rectifier + Smoothing

Fig 6: Transformer + Rectifier + Smoothing + Regulator

Fig 7: Transformer windings           

Fig 8: The transformer schematic

Fig 9: Transformer circuit

Fig 10: Circuit symbol for bridge rectifier

Fig 11: Output: full-wave varying DC       

Fig12 (a): Positive swing of rectification

Fig 12 (b): Negative swing of rectification

Fig 13: The full wave bridge rectifier .

Fig 14:  The output of the rectifier circuit.

Fig 15:  The filtered output of the smoothening capacitor

Fig 16: output signal wave form.

Fig 17: Relay

Fig 18: Circuit diagram on automatic  phase selector









TABLE 4.1: Fair Child Table


TABLE 4.2: Phase Selection Table





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 yearns 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 intelligent phase selector is a system that is capable of comparing three phases and switching automatically to any of the three phases. The system consists of three main parts namely; the transformer, comparators (which is the brain of the system) and electrical switching device (relay).

The transformer used here is the step down type of transformer (it step down 240v to 12v) and these transformer is feed in with different phase voltage, rectified and smooth. Then fed in to a voltage regulator that has positive output. The regulator outputs were connected to comparators. Here the comparators are three in number. We call the comparators the brain of the system because these comparators are connected in a way that each of them will give out an output. The relay in the system is where the output voltage is connected. In this project we even went as far as using pictures for illustration of some components.


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, erases 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/Electronic Engineering” but also to extend their arms to other disciplines, thus enhancing the versatility of Electrical/Electronic 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.


The issue of selecting or switching over manually is now a thing of the past. Nowadays we know that homes and offices enjoy steady power supply once the three phases are available (i.e. red yellow and   blue phases). Is just a question of making a quick and automatic three phase selector?


The scope of the project covers aspects like the features of automatic three phase selector, its applications, and its operations. Its advantages and its components.

Finally, it covers the importance on the need of automatic three phase selector and contributions toward a greater sharing load balance and a better three phase power distribution and monitoring for domestics consumers.


Owning to the nature of this project, the research centers and the resources were not easy to come by within the immediate environment. Some of the limitation encountered on the course of this project include financial and time constrains which did not really take much room for additional capacity beyond what is at hand.


This project will provide lasting solutions to the heavy losses incurred by commercial institution, industries, hospitals, airport etc caused by poor manual selector means and efficient switching facilities. It will also be of use in our household because poor selector of phase manually causes damage to our household equipment  example  electronics like television, radio, video player, etc and electrical appliances like refrigerator, air condition, fans just to mention but a few. Finally, another target is to eliminate the loss of human life due to manual selection of the three phases.


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 phase.


As long as electrical generation and construction is must in everyday activities, electrical power consumption is expected to be reliable and constant supply.

Therefore, what we tend to achieve from this project is;

1.     To have constant power supply.

2.     To have quick operation i.e. phase selection

3.     Reliable power supply

4.     Easy operation

5.     Avoidance of risk in doing manual changeover or switch     


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