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Design And Construction Of Automatic Change-over For Three Phases
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CHAPTER TWO
2.1 LITERATURE REVIEW
The purpose of this project is to design and construct this unique equipment that provider a solution to the power supply problem we are facing in Nigeria today. The automatic change-over switch can be describe as a unique power supply to another as well maintaining constancy in the supply to a particular network load this equipment to be designed and constructed in this project will interface between two different electrical power source (e.g. the main supply and the generator).
The main source of supply to the unit is obtained directly from the public supply (PHCN) the relaying and triggering system serve as an interface between the supply and the load hence the load is not directly couple to the public supply. The triggering units sense the failure in supply and immediately the ignition switch of the generator.
Power change-over switch are two different mode of operation namely.
2.2 MANUAL CHANGE-OVER SWITCH
In this mode of operation when there is any mains failure i.e. (PHCN) outage there is need for personnel to start the generator manually and wait till the generator attains synchronous speed. Only after the generator attains synchronous speed can the operators transfer the load to the generator.
In the event that mains supply is restored the operation has to the operation has to transfer the load back to the mains supply and turn OFF the generator this is done by manually relapsing the change-over breaker. To ensure safety of this operation the two breaker of the change-over switch must be operation are quit cumbersome. Restoration of power is usually a prolonged process which cause delay. The process may also result in heavy losses and damage could be done to sensitive loads during this manual process.
2.3 AUTOMATIC CHANGE-OVER SWITCH
In this mode of operation when there is any mains failure there is no need of the employment of the personnel as the change-over switch will start automatically it sensing power from the mains supply and there after switch the loads to the generator supply upon it attaining synchronous speed. Upon restoration of the mains supply the switch again sense it and transfer the load back to the mains supply.
The type of automatic change-over switch used which differs from the other (semi-conductor controlled switch type) in terms of the type of load transfer or switching panel is the contractors, this design of load transfer panel makes use of mainly relay and contactor combination, its operation is based on the hierarchical rank of contactor relays. It consists of some relays which serves several purpose these are :-
1. Mains Contactor
It carries the bulk of the load its auxiliary when the mains supply (PHCN) in ON, the mains contactor responds to the input by closing its contacts which enable it to get energized causing indicator lamps on the panel to illuminate of these lamps indicate that the mains supply is ON.
2. Mains Auxiliary Contactor
It is usually present in the generator circuit when there is power outage in the mains supply the contact of the mains auxiliary contactor which is in the generator circuit close thereby sending a signal to start the generator
3. Generator Contactor
After starting the generator automatically, the load is then transferred to the generator contactor
4. Generator Auxiliary Contactor
It is the generator auxiliary contactor that is responsible for ensuring that only a power sources gets to the load at point in time. When there is mains supply failure, it break the mains supply line to the load before the generator line is activated. Upon restoration of the mains power supply the generator auxiliary again break the generator line before the load is transferred to the mains supply.
Because this design makes use of relay and contactor combination it is said to have the following advantages
ï¶ It can switch alternating current
ï¶ It can switch high voltage
ï¶ It is useful when high current are to be used
ï¶ It is switch many contacts at once. This quality make them flexible
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ABSRACT - [ Total Page(s): 1 ]ABSTRACT The main aim of any electric power supply in the world is to provide uninterrupted power supply at all times to all its consumers. Although in developing countries, the electric power generated to meet the demands of the growing consumers of electricity is insufficient hence instability and outage. Power instability or outage in general does not promote development in the public and private sector. The inventors do not feel secure to come into a country with constant or freq ... Continue reading---
APPENDIX A - [ Total Page(s): 1 ]BILL OF ENGENEERING MEARSUREMENT AND EVALUTION (BEME)The table below shows the cost estimate in naira and kobo of constructed automatic change-over panel.Bill of Engineering Measurement and Evaluation ... Continue reading---
TABLE OF CONTENTS - [ Total Page(s): 1 ]TABLE OF CONTENTS Title Page Certification Acknowledgements Abstract Table of Contents CHAPTER ONE1.1 Introduction 1.2 Aim and Objective of the Project 1.3 Scope of the Project CHAPTER TWO2.1 Literature Review 2.2 Manual Change-over Switch 2.3 Automatic Change-over Switch 2.4 Related Work 2.5 Reasons for Automatic Change-over Switch 2.6 Problems of Automatic Change-over Switch CHAPTER THREE3.1 Methodolog ... Continue reading---
CHAPTER ONE - [ Total Page(s): 1 ]CHAPTER ONE1.1 INTRODUCTION Power 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 is requiring as the rate of power outages become predominantly high. Research in the field of electrical electronics engineering has led to the tremendous discovers and inventions especially in the area of automation and power control. These invention have been useful in solvi ... Continue reading---
CHAPTER THREE - [ Total Page(s): 4 ]START AND STOP BUTTONS These two push buttons are used to close and open the circuit respectively. The start push button is a normally open type (NO) while the stop push button is a normally close (NO) type to breaker the circuit when need arise3.5 CONTACTOR Is a device designed for repeatedly making and breaking an electronic power circuit. It is usually operated magnetically. It can be operated in line or be remotely governed by pilot devices or relay. And when there is a s ... Continue reading---
CHAPTER FOUR - [ Total Page(s): 4 ]CHAPTER FOURCONSTRUCTION4.1 LIST OF COMPONENT USEDThe following electronic components used in the project are list below(1) Voltmeter (2) Casing (3) Vero-Board(4) Transformers DC 12V(5) Diodes (6) Capacitors 100(7) Resistors 4k(8) Contactors (9) 16mm2 Cables(10) 1ooAmp connector (11) Bolt and Nuts(12) Indictor light (13) Relay three phase (14) 555IC timer 4.2 VERO BOARD: is a brand of strip-board, a p ... Continue reading---
CHAPTER FIVE - [ Total Page(s): 1 ]CHAPTER FIVE5.1 CONCLUSION The automatic change-over switch has immense advantage in every area where power is required it is a fact that there is hardly any aspect of human life were electrical power is not required, at home, offices, hospital, etc. It find a wide application scope, wherever the re-ability of electrical supply is necessary, for switching to an alternative source from main.5.2 RECOMMENDATIONThe automatic change-over switch is needed in every home and of ... Continue reading---
REFRENCES - [ Total Page(s): 1 ]REFERENCEB.L. and A.K. Theraja (1997): Electrical Technology, S. chand company LTDEngr. A.O Aduloju (2003): Electrical Power System, Evidence Nigeria VentureEngr. M.B Jenyo (2007): Electrical Power System III & IV lecture Notes, UnpublishedEngr. T.A. Mustapha (2006): Electrical Power System I & II inn lecture Notes, unpublishedInternet Research: http://www.electricalsolution.comM.S. Ahmed, A.S. Mohammed & C.B. Augusibo (2006): Development of a single Automatic change-over switch Federal Universi ... Continue reading---
