Description
This project work is on the design and construction of automatic changeover for 3-phase power supply. It provides a means of switching from one phase of AC mains to another in the case of failure in the existing phase; This project has been improved on the existing types of electromechanical device that has being in use over the years.
Hence this has been achieved by the use of operational amplifier, timing circuit and high current relay switches and it is powered by 12V dc power supply.
The aim of this work is to design and construct an Auto changeover introduces an automatic solution to overcome power fluctuation/phase interruption by selecting next most healthy available phase to feed the equipment without any notice of power outage.
TABLE OF CONTENTS
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRCT
TABLE OF CONTENT
CHAPTER ONE
- INTRODUCTION
- BACKGROUND OF THE PROJECT
- AIM/OBJECTIVE OF THE PROJECT
- SIGNIFICANCE OF THE PROJECT
- PURPOSE OF THE PROJECT
- STATEMENT OF PPROBLEM
- LIMITATION OF THE PROJECT
- APPLICATION OF THE PROJECT
- DEFINITION OF TERMS
- PROJECT ORGANISATION
CHAPTER TWO
LITERATURE REVIEW
2.0 LITERATURE REVIEW
2.1 REVIEW OF ELECTRICAL PHASES
2.2 REVIEW OF THREE-PHASE ELECTRIC POWER
2.3 REVIEW OF CAUSES OF POWER FAILURES
2.4 POWER SUPPLY RELIABILITY
CHAPTER THREE
3.0 CONSTRUCTION METHODOLOGY
3.1 BLOCK DIAGRAM OF THE SYSTEM
3.2 CIRCUIT DIAGRAM
3.3 CIRCUIT DESCRIPTION
3.4 SYSTEM OPERATION
3.5 COMPONENTS LIST
3.6 DESCRIPTION OF MAJOR COMPONENTS USED
CHAPTER FOUR
4.0 RESULT ANALYSIS
4.1 CONSTRUCTION PROCEDURE AND TESTING
4.2 ASSEMBLING OF SECTIONS
4.3 CONSRUCTION OF THE CASING
4.4 ECONOMIC OF THE PROJECT
4.5 PROJECT VIABILITY
4.6 PROJECT RELIABILITY
4.7 PROJECT MAINTAINABILITY
4.8 PROJECT EVALUATION
4.9 TESTING, TROUBLESHOOTING AND REMEDY
CHAPTER FIVE
- CONCLUSIONS
- RECOMMENDATION
5.3 REFERENCES
CHAPTER ONE
- INTRODUCTION
In Nigeria today the problems of power outage across phases is so rampant thus leading to some sensitive equipment and appliances being redundant, this could sometimes be the cause of one phase going out with respect to the other.
It may surprise one to note that in an attempt to solve this problems, so many unskilled electricity consumers has in recent past resorted to some crude means of swapping between phases to obtain power. So many souls have been lost in this act. This is an undesirable condition to consumers and the need now arises to design a device that can automatically select among the phases and make power supply available at the consumers terminal.
However, this can only be possible if one have a three phase met or and there is supply from any of the service line or the entire line, this project known as a three phase automatic phase selector has been constructed with a view of solving the problems stated above. The design and construction was based on the principle of Electro magneto-Dynamism and alignment as demonstrated in the contactor arrangement.
Among other components are the timers miniature-circuit breakers the contactors and indicator bulbs, the ease with which the device is operated is well elaborated to ensure simplicity effort were made to present a stop by step operation of the project. As much as there is no project without limitation and applications, we have as well dedicated a section of this paper to look into it.
In order to ease the effort of technicians in restoring the devices should there be any malfunction associated.
Faults and how they are cleared is presented, however, there are no user serviceable parts in the device therefore all maintenance should be referred to a qualified electrical personnel.
- BACKGROUND OF THE PROJECT
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.
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.
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.
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.
In view of these considerations, this project is aimed at designing and constructing a workable automatic change over switch with a phase failure detecting circuit also known as “Automatic Mains Failure” which switches on the head from power Holding Company (PHC) to a generator when power fails and from generator to PHC when power comes back.
1.2 OBJECTIVE OF THE PROJECT
The objective of this work is to design a device that will overcome power fluctuation phase interruption by selecting next most healthy available phase to feed the equipment.
1.3 SIGNIFICANCE OF THE PROJECT
Industries require three phases power to run their machinery. Some of them require continuous \ uninterrupted power to maintain their data. Auto phase selector unit for those equipment whose supply is single phase. The single phase supply is selected automatically from three phases supply.
Auto changeover introduces an automatic solution to overcome power fluctuation \ phase interruption by selecting next most healthy available phase to feed the equipment.
1.4 STATEMENT OF THE PROBLEMS
In every home, office or industries, automatic changeover plays a vital role, that is, It provides a means of switching from one phase of AC mains to another in the case of failure in the existing phase; This project has been improved on the existing types of electromechanical device that has being in use over the years.
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..
1.5 SCOPE AND LIMITATION OF THE STUDY
This work covers only a three phase automatic changeover 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
1.7 APPLICATION OF THE PROJECT
Some common examples of entities that implement automatic switches out of necessity are: hospitals, data centers, jails and prisons, fire departments, defense organizations, and police departments.
1.8 DEFINITION OF TERMS
CHANGEOVER: Generally, a changeover switch is a system which could be operated manually or automatically , that changes one source of power supply to another source in case of power failure from either of the two sources.
RELAY: relay is one of the major components used in this work which is an electrical device, typically incorporating an electromagnet, which is activated by a current or signal in one circuit to open or close another circuit.
POWER FLUCTUATIONS: is a periodic dip or spikes in the electrical current of any given circuit.
POWER FAILURE: is a short- or long-term loss of the electric power to an area.
1.9 PROJECT WORK ORGANISATION
The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:
Chapter one of this works is on the introduction to changeover switch. In this chapter, the background, significance, objective limitation and problem of changeover switch were discussed.
Chapter two is on literature review of changeover switch. In this chapter, all the literature pertaining to this work was reviewed.
Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.
Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.
Chapter five is on conclusion, recommendation and references.
CHAPTER FIVE
5.0 SUMMARY
Phase selector provides a means of switching from one phase of AC mains to another in the case of failure in the existing phase; it also changeover to generator if there is failure in all the three phases of the AC mains.
In three-phase applications, if low voltage is available in any one or two phases, and you want your equipment to work on normal voltage, this circuit will solve your problem. However, a proper-rating fuse needs to be used in the input lines (R, Y and B) of each phase. The circuit provides correct voltage in the same power supply lines through relays from the other phase where correct voltage is available.
The distribution line supplying your home may be single phase and have only two wires strung between the poles (we will use the overhead power lines as examples because they can be easily seen). However, the distribution line may be made up of 4 lines. What are the others? The other lines carry the currents from two other electrical circuits, making a total of three circuits or phases. The reason why there are only 4 lines is because the 3 phases have a common neutral line (i.e. 3 active lines and 1 common neutral line).
Because the magnitude and direction of the electricity flowing in each of the phases is slightly displaced in time from the electricity flowing in the other phases, the current flowing in the common neutral will be the sum of the neutral currents from the 3 phases. The resultant current in the common neutral is smaller in a 3 phase system than in systems with other numbers of phases. This ability to use a common neutral of relatively small capacity has large economic advantages and is the main reason why 3 phases are used.
3 phase electricity has another advantage. We mentioned above that, in Canada, the voltage between the active and neutral in the single phase, low voltage supply to our homes is 220 volts and that this phase is only one of the phases in the 3 phase system. The voltage between the phases of a 220/220V 3 phase system is 240 volts (in Canada). A 240 volt, 3 phase supply is able to deliver more energy than a 120 volt, single phase supply. 3 phase supplies are normally restricted to large electrical loads, such as large electric motors. Commercial buildings are often wired for three phase power. Air conditioners for instance are run on the three phase power while single phase power is typically used for most electrical, electronic and lighting equipment.
A single phase supply must have a neutral, whereas a 3 phase supply does not require a neutral. More complicated reasons deal with fixing the voltage of the single phase supply relative to the ground (because domestic appliances have their metal enclosures connected to ground) and for fault protection purposes. 3 phase, medium voltage, distribution systems and high voltage transmission systems therefore use one wire for each phase and no neutral.
5.2 CONCLUSION
The mains supply in Nigeria fluctuates widely due to overloading, ageing and improper distribution of loads among the three phases of the consumers’ substation transformer.
Appliances such as video cassette player, television as well as those containing compressors like air conditioners, refrigerators, etc could be damaged due to this variation and fluctuation in voltage mains.
The automatic three-phase selector is an electronic circuit that is capable of detecting voltage levels by means of a controller that does some level of comparison before initializing a logic combinational circuit that does some logic combination before initializing an electronic relay switch action. The relay is energize only when the mains voltage is within an accepted predetermined limit, outside of which relay remains dormant .voltage levels below the desired range is ignored. This device is designed to work with a 3-phase input signal. The device functions in the form of an automatic electronic switch, switching between three potentials, with the aim of supplying the highest potential to the load.
5.3 RECOMMENDATION
Carrying-out this work by final year student is a right thing and at the right time.
This work was built with quality wiring and contains many connections, I recommend that if failure occur, it should be troubleshoot by a qualify personnel along with the circuits diagram.
This project was built for Educational purposes. If one want to use it for industrial or home applications, I recommend that a hook should be attached to the casing that would allow fixing the system on the wall.
