Design And Construction Of Automatic Phase Selector

TABLE OF CONTENT

DECLARATION                                                                                                                    i  CERTIFICATION                                                                                                                  ii  DEDICATION                                                                                                                        iii  ACKNOWLEDGEMENTS                                                                                                    iv   TABLE OF CONTENTS                                                                                                       v  LIST OF TABLES                                                                                                                 vii

LIST OF FIGURES                                                                                                               viii

ABSTRACT                                                                                                                            ix  CHAPTER ONE:INTRODUCTION                                                                                   1

1.1 Background Of The Study                                                                                                 1

1.2 Aim And Objectives                                                                                                          2

1.3 Justification                                                                                                                        3

1.4 Scope And Limitation                                                                                                        4

1.5 Significant of study                                                                                                            4  1.6 Defination Of Terms                                                                                                          4

CHAPTER TWO: LITERATURE REVIEW                                                                     6

2.0 Basic Concept                                                                                                                    6

2.1 Effect Of Power Failure                                                                                                     6

2.2 Equipment Voltage Subceptivility                                                                                     7  2.3   System Interactions And Solutions                                                                                  8

2.4. Review of The previous work                                                                                          10  2.4.1  phase selection by manual contro                                                                                  l1

2.4.2  phase selection by sequential logic contro                                                                    11  2.4.3  phase selection by camparator contro                                                                            l2

CHAPTER THREE:METHODOLOGY                                                                            13

3.1 Material selection                                                                                                              13

3. Principle Of Operation 13   3.3. Design Specification                                                                                                        14  3.4.  Power Supply Unit                                                                                                          14  3.5.Voltage Sensing Unit                                                                                                         16
   • Logic Control Unit 17
   • Switching/Output Unit 19

• Operational Descreption 20

3.8.1 Transformer                                                                                                                     20

3.8. 2 Conparator                                                                                                                      20

• 3The Relay as Switching Circuit 22
  • Comprehensive circuit diagram 23
  • Design implmentation 24  11 Construction methods                                                                                                      25  3.12 Packaging                                                                                                                         25

CHAPTER FOUR: RESULT AND DISCUSSION                                                            26

4.1Tests and result                                                                                                                   26

4.2 Discution of result                                                                                                              27

4.3 Relay and contactor consideration                                                                                     28  4.4 Problem encoutered                                                                                                           29

CHAPTER FIVE:SUMMARY, RECOMMENDATION AND CONCLUSION            30

5.1 Summary                                                                                                                            30

5.2 Conclusion                                                                                                                         31 Recommendation                                                                                                                31

 

ABSTRACT

Power instability and phase failure has posed serious threat to economic development in Nigeria. Most companies; industrial, commercial and even domestic are dependent on public power supply which have erratic supply such as phase failure, phase imbalances or total power failure due to one or more technical problem in power generation, transmission or distribution. Much time would be wasted in the process of manual change over. This means that time and the process needed for the phase change may cause serious damages to machines even the products and may pose a threat to the life of the person while moving from one phase to a more suitable one.Hence, there is need for automation of phase change during phase failure or total power failure in order to safe guard consumer appliances from epileptic power supply. The following objective were achieved; to develop a simple low cost device aimed at easing the prevalent burden faced by delicate industries and institutions electrical equipment’s, to reduce the damages caused to our household equipment’s, eliminating the loss of human life due to electric shock from the manual selection of the three phases during supply of high voltage.The automatic three phase power system selector was designed and constructed. The device automatically switches over to the alternative phase that has voltage when there is power outage or extremely low voltage in the phase which the load is connected without the power going off. The selector links the load and the other phases and relay switches allowing the usage of the remaining phases where there is outage on the mains source without disturbing or interrupting the load. It maintains constant power supply to the load by automatically activating the phases when the need arises.the specification of Output power, Frequency, Input voltage, and output voltage of the designed Automatic Three phase selector are,Output power=500W, Frequency=50Hz,Input voltage =12V_dcand Output voltage=18V_ac.The device reduced the possibility of power being off completely in case of power failure in any particular phase if users connect their electronics gadget to it and reduced the response time needed to switch from one phase to another. It is recommended that a software model of the design should be developed and simulated to enable further research and improve the performance of the system.

 

 

CHAPTER ONE INTRODUCTION

1.1    Background of the Study

Power supply in Nigeria and most developing countries of the world is anything but stable. This has adverse effects on the consumers of the electricity and the equipment that are operated from the mains sources of electricity supply in these parts of the world. Power instability and phase failure has posed serious threat to their economic development (khairul, et al., 2011). This means where there is an erratic power supply, there is no development. However, most companies; Industrial, commercial and even domestic are dependent on public power supply which have erratic supply such as phase failure, phase imbalances or total power failure due to one or more technical problem in power generation, transmission or distribution (Adedokun,and osunpidan., 2010). Hence, there is need for automation of phase change during phase failure or total power failure in order to safe guard consumer appliances from epileptic power supply.

In most cases, many manufacturing companies, be it domestic or industrial, which employ single phase equipment for its operation, sometimes experience challenges during unbalance voltages, overloads and under-voltages, in power supply, much time would be required in the process of manual change over. This means that time and the process needed for the phase change may cause serious damages to machines and even the products, hence, there is need for automatic phase switching system. Considering also a case where a single phase public utility prepaid meter is operated with a single phase power supply unit and there is phase failure from the public utility power supply, the prepaid meter will stop reading. At this point, if the phase is not manually changed, the single phase prepaid meter will stop reading. That is to say someone needs to be present always to make the changes at any point in time. But to overcome these protocols, automatic systems need to be used.

The automatic 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 electromechanical switching devices (relay/contactors). A step down type transformer (it steps down 220 V_ac to

18 V_ac) was used and fed in with different phase voltages, rectified, smoothened and regulated. The regulator outputs were connected to comparators. The 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.

The importance and advancement of control system in engineering have created different ways in which automatic switching systems can solve domestic and industrial problems especially in the developing countries.

This project involves the use of transistor driven relays and contactors to effect an automatic change of phase whenever the voltage condition becomes intolerable in the previous phase connected. The design of this circuit involves the use of electromechanical switches but the details of design varies depending on the type of load involved.

1.2 Aim and Objectives

The aim of this work is to design a device that will overcome the challenge of switching over manually during phase interruption or power fluctuation by automatically selecting the next healthiest available phase to feed the equipment. In the implementation of this, the following objective were achieved:-

1. To develop a simple low cost device aimed at easing the prevalent burden faced by delicate industries and institutions electrical equipment’s. 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 from the face of progress of work in such offices.

1. To enhance a greater sharing load balance and a better three phase power distribution and monitoring for industrial and domestic consumers.

• To provide lasting solutions to the heavy losses incurred by commercial institution, industries, hospitals, airport etc. Caused by poor manual selector means and inefficient switching facilities.

1. To reduce the damages caused to our household equipment’s example electronics like television, radio, video-player etc. And electrical appliances like refrigerator, air condition fans which is usually a result of poor selector of phase manually.
2. It is also aimed at eliminating the loss of human life due to electric shock from the manual selection of the three phases, during supply of high voltage.

1.3 Justification

Industries require three phases power to run their machinery. Some of them require continuous or uninterrupted power to maintain their data. Auto phase selector unit is basically for those equipment whose supply is single phase. The single phase supply is selected automatically from three phases supply. Auto Phase Selector introduces an automatic solution to overcome power fluctuation and phase interruption by selecting next most healthy available phase to feed the equipment.

Most homes and offices should enjoy steady power supply once the three phases are available (i.e. red yellow and blue phases). It is just a question of making a quick and automatic three phase selection.

  

1.4 Scope and Limitation

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 industrial and domestic consumers.

This work covers only a three phase automatic phase selector which can only be used for providing a means of switching from one phase of AC mains to another in the case of failure in the existing phase.

1.5 Significance of Study

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 work in several facets of human endeavour makes this work really important to humanity.

The use of the device produced from this 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.

1.6 Definition of Terms

Resistor: is a passive two terminal electrical component that implements electric resistance as circuit element. Resistors act to reduce current flow and at the same time act to lower voltage levels within circuit.

Variable Resistor: is an electronic component, which is used in an electronic circuit for adjusting circuit resistance to control voltage or current of the circuit or part of the circuit.

 Transistor: this is a semiconductor device used to amplify and switch electronic signals and electric power.

Capacitor: is a passive two terminal electric component used to store electrical energy temporarily in an electric field.

Contactor: a relay used to control an electrical power circuit.

Diode: is a device which only allow unidirectional flow of current if operated within a rated specified voltage level.

Transformer: is a device that changes (transforms) and alternating potential difference (voltage) from one value to another value be it smaller or greater using the principle of electromagnetic induction.

Comparator: is an electronic component that compares two input voltage. It is designed to operate with positive feedback and with it output saturation at one power rail or the other.

Design And Construction Of Automatic Phase Selector

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