ASSESSMENT OF OCCUPATIONAL EXPOSURE AND RADIATION PROTECTION IN SOME SELECTED WELL-LOGGING AND INDUSTRIAL RADIOGRAPHY FACILITIES IN NIGERIA

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

Nigeria has, for a very longtime, engaged in the peaceful application of nuclear technology. The use of ionizing radiation, because of its unique properties, has considerably increased over the years in oil and gas industry.

Due to the adverse health effect when people are over-exposed to ionizing radiation, radiation is feared by many, worldwide, and Nigerians are no exception. This concern is even much higher with inhabitants living at close proximity to nuclear establishments and other facilities using ionizing radiation sources. What most people do not realize is that radiation is present everywhere, in everything in the environment and even in the bodies (Oyeyinka et al, 2012). There is cosmic radiation made up of protons, alpha particles and heavy nuclei bombarding the earth from space which, upon interaction with the atmosphere results into large assortment of secondary particles, including pie (π) and mu (µ) mesons, electromagnetic photons, neutrons, protons and electrons contributing high radiation dose burden to man even at sea level (Maduemezia et al, 2008).

Other natural radiation includes the terrestrial gamma rays from land, sea and walls of houses we live. Humans are also internally exposed from radiation emitted by radionuclides absorbed into the body through the consumed food (Oyeyinka et al, 2012). Examples of such radionuclides are potassium-40, heavy elements and carbon-14. Therefore, living isolated from radiation is almost impossible in the modern world as humans and animals are subjected to both natural and artificial radiation in the environment, due to increase in living standard (Zakari et al, 2009). There is no need for fear of radiation but there is the need to understand its properties, make use of it and reduce the exposure to dose levels which the society judged as acceptable, with minimum associated risk. As long as the contribution from the artificial radionuclides does not push the annual dose equivalent level beyond 1mSv for the public and 20mSv averaged over five years for classified workers, then there is no need to fear radiation (NNRA, 2003).

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ASSESSMENT OF OCCUPATIONAL EXPOSURE AND RADIATION PROTECTION IN SOME SELECTED WELL-LOGGING AND INDUSTRIAL RADIOGRAPHY FACILITIES IN NIGERIA

ASSESSMENT OF TOBACCO COMPANY EFFLUENT FOR RADIOACTIVITY AND OTHER PARAMETERS FOR GROUNDWATER AROUND THE COMPANY IN CHIKAJI, ZARIA, KADUNA, NIGERIA

CHAPTER ONE

INTRODUCTION

1.1 Background

Drinking water sourced from deep wells and boreholes are usually expected to have high concentration of radioactive nuclides. This is because they pass through fractures in bedrocks or within the soil which contains minerals deposits that might have radioactive constituents and thus leaking into the water ways. Radioactivity in drinking water is one of the major ways in which radionuclides from the environment gets into the human body, which might consequently lead to radiation-induced disorderness (USEPA, 2010). There is evidence from both human and animal studies that radiation exposure at low to moderate doses may increase the long term incidence of cancer and that the rate of genetic malformations may be increased by radiation over exposure (Otton, 1994). It is therefore important to determine the amount of radioactivity in drinking water for every area where people live in, so as to guard against its health hazards (WHO, 2006).

Groundwater could be contaminated by radioactive materials because terrestrial radioactivity increases with depth in the earth crust (WHO, 1998). These radioactive materials occur naturally and of most concern are the uranium and thorium series and the progenies (radon and thoron). They contribute to the radioactivity of the rain and groundwater which in turn affects drinking water. Due to these, drinking water from deep wells and boreholes are expected to contain high concentrations of radioactive elements. Radioactive materials could also be washed into wells, boreholes and even enter through burst pipes. Important radioactive elements in drinking water are tritium, potassium-40, radium and radon which are alpha or beta emitters (Surbeck, 1995). People who ingest polluted water can develop illness and with prolonged exposure to radioactive polluted water could cause cancers, toxicity of the kidneys or bear children with birth defects (WHO, 2006). Knowledge of the naturally occurring radionuclide present in drinking water enables one to assess any possible radiological hazards to humans by the use of such water.

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ASSESSMENT OF TOBACCO COMPANY EFFLUENT FOR RADIOACTIVITY AND OTHER PARAMETERS FOR GROUNDWATER AROUND THE COMPANY IN CHIKAJI, ZARIA, KADUNA, NIGERIA

CHARACTERIZATION OF ANTIBIOTIC RESISTANCE GENES FROM SALMONELLA ASSOCIATED WITH INVASIVE SALMONELLOSIS IN SELECTED HOSPITALS IN KATSINA STATE, NIGERIA

CHAPTER ONE

1.0 INTRODUCTION

Salmonellae are Gram negative, non-sporing, motile, and non-lactose fermenting rods. They belong to the phylum Proteobacteria, class Gamma-proteobacteria, order Enterobacteriales, family Enterobacteriaceae and genus; Salmonella. With the exception of Salmonella Pullorun and Salmonella gallinarumall Salmonellae are motile, also with the exception of Salmonella typhi all are non-capsulated. The genus was named in honor of Daniel Elmer Salmon an American Veterinary Pathologist (Graham 2009 ; FDA/CFSAN, 2009).

Salmonellae can be divided into two major groups for the purpose of understanding of the genus. Group one includes the members of the genus that involved the most invasive salmonellae which cause enteric fever/typhoid fever (Typhoidal Salmonellosis) and group two are the Non-typhoidal salmonellosis (NTS) (Graham 2009).

An infection (salmonellosis) is caused by ingesting salmonellae in food that has been contaminated with animal or human intestinal sources directly or indirectly (Redmond and Griffith,2003). Common sources of the infection are contaminated foods such as poultry meat and meat products, eggs and eggs products or water (Udezeet al.,2010). Once the bacteria are in the body, the incubation period is only about 8 to 48 hours(Willey et al., 2008). The disease results from a true food borne infection because the bacteria multiply and invade the intestinal mucosa where they produce an enterotoxin that destroys the epithelial cells. Abdominal pain, cramps, diarrhea, nausea, vomiting, and fever are the most prominent symptoms, which usually persist for 2 – 5 days but can last for several weeks (Willey et al.,2008). During the acute phase of the infection as many as one billion salmonellae can be found per gram of faeces. Most adult patients recover, but the loss of fluids can cause problems for children and elders, blood and mucous may be present in faecal specimen (Al-jurayyanet al., 2004). Salmonellae can be isolated from stool, food, blood, urine, bone narrow and duodenal aspirates. From blood the organisms can be detected in about 75-90% of patients during the first ten days of infection, and in about 30% of patients during the third week. From faeces, organisms can usually be isolated from about 40% to 50% of patients during the second week of infection and about 80% of patients during the third week (Cheesborough, 2002).

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CHARACTERIZATION OF ANTIBIOTIC RESISTANCE GENES FROM SALMONELLA ASSOCIATED WITH INVASIVE SALMONELLOSIS IN SELECTED HOSPITALS IN KATSINA STATE, NIGERIA

A COMPARATIVE CALCULATION OF DOSE RATE USING RAD PRO CALCULATOR FOR SHIELDING REQUIREMENTS OF COBALT-60 AND CESIUM-137 SOURCES AT CERT.

CHAPTER ONE

1.0 INTRODUCTION

1.1 General Background

The term shielding implies the deliberate introduction of material between the radiation and an object to reduce radiation intensity and damage to the object. This is preferred method of controlling radiation because it results in intrinsic safe working conditions (Martin and Harbison, 1980). The type of shielding used and the thickness require depend on the type of radiation, its energy, the flux and the dimension of the source (Esien-umo, 2007).

1.1.1 Shielding of x-ray generators:

The hazards of x rays were recognized within months of Roentgen’s 1895 discovery, but dose limitation by time, distance, and shielding was at the discretion of the individual practitioner until about 1913. Only then were there organized professional efforts to establish guides for radiation protection, and not until about 1925 were there instruments available to quantify radiation exposure. In his monumental survey of organization for radiation protection, Taylor (1979) begins with British and German efforts at establishing guidance for x-ray shielding. In 1913, the German Radiological Society on X-Ray Protection Measures issued recommendations that 2 mm of lead shielding was needed, regardless of generator voltage, workload, or filtration. In Britain, the Roentgen Society addressed radiation protection, stressing operator protection, the need for beam collimation, and the importance of scattered X rays. No explicit recommendations on shielding requirements were issued.

1.1.2 Shielding of Radium sources:

In 1927, the International Committee on X-Ray and Radium Protection issued the following recommendations for storage of radium sources. Tubes and applicators should have at least 5 cm of lead shielding per 100 mg of radium. Radium solutions required lead shielding ranging from 15 cm for a 0.5 g source to 30 cm for a 2g source. NCRP Report 2 (1934) specified a 3-m protective zone around stored Ra sources, and recommended exhaust fans or hoods for removal of radon and decay products escaping from unsealed sources. Shielding of stored sources was revised to 4 cm of lead for 100 mg to 6 cm for 300 mg. NCRP Report 4 (1938) addressed dosimetry for gamma rays emitted from radium sources. It was not until 1941 that there was established a tolerance dose for radium, expressed in terms of a maximum permissible body burden of 0.1 Ci. This was done largely in consideration of the experiences of early “radium-dial” painters and the need for standards on safe handling of radioactive luminous compounds (NCRP, 1941).

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A COMPARATIVE CALCULATION OF DOSE RATE USING RAD PRO CALCULATOR FOR SHIELDING REQUIREMENTS OF COBALT-60 AND CESIUM-137 SOURCES AT CERT.

DESIGN AND CONSTRUCTION OF A PYRAMID-SHAPED SOLAR .A RESEARCH PROJECT MATERIAL ON PHYSICS

CHAPTER ONE

1.1 INTRODUCTION

Distilled water is needed for drinking, irrigation and for many other applications. A diversity of approaches are used for these portions of fresh water from saline water; namely multi stage flash (MSF), multiple effect (ME), reverse osmosis (RO), electrodialysis, ion exchange, phase change, and solvent extraction. These methods are expensive, however, for the production of small amount of fresh water. The development of solar distillation has demonstrated its suitability for the desalination process when the weather conditions are suitable and the demand is not too large, i.e. less than 200 m³/d. The problem of low daily productivity of the solar stills triggered scientists to investigate various means of improving the stills productivity and thermal efficiency.

Different aspects of triangular-shaped solar stills (CSS), also called double slope stills, have been studied. Production in this still is influenced by the orientation, as shown by (Singh et al., 1995) who found the maximum yield for a cover with east–west. Detailed studies of heat transfer coefficients can also be found, (Sharma and Mullick, 1991), in which energy transfer mechanisms, such as convection, evaporation and radiation are investigated, and new empirical relations to estimate cover temperatures are proposed. To model heat and mass transfer in solar stills ( Dunkle, 1961) proposed the use of a correlation of the form where C is 0.075 and n is 1/3 for air enclosed between horizontal parallel plates. This correlation is expressed in terms of a modified temperature difference that includes molecular weight and buoyancy, and considers the cover as a single element. This has been the most widely accepted model for solar stills and describes the basic heat and mass transport mechanism between heated water mass and a condenser.

1.2 PROBLEM DESCRIPTION AND SIGNIFICANCE

Many parts of the world do not have access to a suitable source of clean drinking water. Most of the water available in streams, lakes, rivers, sea, etc. carries parasites or diseases, or is simply not fit for consumption and therefore is a significant health hazard. Areas without access to clean water are also usually poverty stricken and do not have the infrastructure necessary to create and support large scale water purification plants. Thus, there is need for a small scale, affordable water purification system for individual families or villages. Africa has the second largest population of people without access to clean drinking water.

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DESIGN AND CONSTRUCTION OF A PYRAMID-SHAPED SOLAR .A RESEARCH PROJECT MATERIAL ON PHYSICS

THE DETERMINATION OF THE RELATIONSHIP BETWEEN THE WEIGHT AND AGE OF MALE AND FEMALE STUDENTS IN DELTA STATE UNIVERSITY, ABRAKA. A RESEARCH PROJECT MATERIAL ON PHYSICS

CHAPTER ONE

INTRODUCTION

BACKGROUND OF STUDY

Gender, age and weight are the fundamental indices of human growth, which are strongly affected by various factors such as genetic effects, race, nutrition, congenital disease, and so on. Anthropometric measures have been widely used for body weight classification in humans. Basically, the weight and age distributions for different sex are most widely used in the assessment of the health status and various physiological processes as well as for many other research and commercial purposes. The weight and age relationship from birth through maturity is represented by three segments or physiologic age intervals-infancy, childhood and adulthood (Gross et al., 2005).

The beginning of biological growth and development during adolescence is signified by the onset of puberty, which is often defined as the physical transformation of a child into an adult. A myriad of biological changes occur during puberty including sexual maturation, increases in height and weight, completion of skeletal growth accompanied by a marked increase in skeletal mass, and changes in body composition. The succession of these events during puberty is consistent among adolescents; however, there may be a great deal of deviation in the age of onset, duration, and tempo of these events between and within individuals (Wong et al., 1995).

Body shape or body weight is an important element of the intricate mechanism of one’s own identity. Weight is really the ratio of lean body mass to fat body mass. The relationship between the indices and physical conditions of weight and sex of an individual has been extensively studied by Eknoyan, (2008) with an aim to establish an anthropometric measurement for body mass index (BMI). The weight and age of an individual can be useful in determining its’ center of mass which is nearly the geometric center of a person and this differs across males and females of different age group. More so, there is a growing clinical interest in body composition between males and females most especially their percentage body fat due to the evidence that links body composition with health risks and the development of certain diseases.

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THE DETERMINATION OF THE RELATIONSHIP BETWEEN THE WEIGHT AND AGE OF MALE AND FEMALE STUDENTS IN DELTA STATE UNIVERSITY, ABRAKA. A RESEARCH PROJECT MATERIAL ON PHYSICS

THE DESIGN, CONSTRUCTION AND TEST ON A TWO STATION SIMPLE INTERCOM SYSTEM

THE DESIGN, CONSTRUCTION AND TEST ON A TWO STATION SIMPLE INTERCOM SYSTEM. A RESEARCH PROJECT MATERIAL ON PHYSICS

CHAPTER ONE: INTRODUCTION

1.1 INTRODUCTION / BACKGROUND

Human to human communication is an essential part of our everyday activities. Advances in communication technology have enabled any-time-anywhere connection between people. There are a wide variety of devices to communicate with family, friends and workgroup members who are distributed geographically. Cellular phones are used at the working places, stores etc. to call home to be reminded of what is needed or when one will be late to work, meeting etc.

The purpose of a communication system is to transfer information between two or more points. In general, a communications system requires three things namely; a transmitter, a propagation medium, and a receiver. The information to be transferred may be in analog form (example, voice or audio) as in the case of this study where voice is the source of information, or in digital form (computer data, digitalized voice, and so on). The transmitter must have some means of superimposing this information onto its output signal (modulation). The modulated transmitter signal must pass through a propagation medium to a receiver. The propagation medium may be free space, an RF transmission line, or a fiber optic

cable. The function of the receiver is to select (filter) the desired signal, amplify and extract the information. A simplified block diagram of a typical communication system is shown on figure 1. 0 below.

Interest arises in promoting communication within a building which is difficult and stressful going from one point to another within the building in the name of delivering information. In a domestic setting, family members will be collocated within the same building, but often will be unable to be heard using a normal speaking voice. Many households utilize intercom systems to facilitate conversations between remote parts of the home, but these systems have their drawbacks. They require one or both parties to go to specific parts of the house or hold onto a handset in order to communicate. They also offer little ability to direct communication to a person, within the house when the location of the person is initially unknown.

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THE DESIGN, CONSTRUCTION AND TEST ON A TWO STATION SIMPLE INTERCOM SYSTEM. A RESEARCH PROJECT MATERIAL ON PHYSICS

A GEOPHYSICAL INVESTIGATION USING SEISMIC REFRACTION METHOD TO DETERMINE THE CAUSES OF ROAD FAILURE, A CASE STUDY OF IRUEKPEN-OZALLA ROAD AXIS. A RESEARCH PROJECT MATERIAL ON PHYSICS

ABSTRACT

This project work was carried out at Ireukpen-Ozalla Road Axis Ekpoma, Esan-West Local Government Area Edo State. Using seismic refraction prospecting method to examine the cause(s) of the persistent failure of the road. An ABEM TERRALOC MARK-6 Seismometer was used as the recording instrument and twelve geophones as wave detectors in series with one another. The geophones were spread at predetermined distances and the impact of a sledge hammer on a flat plate served as the source of generating seismic waves. The “SERCOM1” software was employed in the interpretation of the field result for the forward and reversed shooting respectively. From which the subsurface reveals two layers of velocities, which are 980ms-1 and 1283ms-1 for the forward shooting, 851ms-1 and 1276ms-1 for the reversed shooting respectively. The investigation also shows that at twenty three metres (23 m) from the surface of the forward shooting, clay deposit could be discovered. And even at thirteen metres (13 m) from the surface of the reversed shooting clay deposit could also be encountered. The form of road failure identified in this study is due to subsidence associated with clayey material and the delineated clayey water absorbing sections which are major geologic factors responsible for road failure in the area.

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A GEOPHYSICAL INVESTIGATION USING SEISMIC REFRACTION METHOD TO DETERMINE THE CAUSES OF ROAD FAILURE, A CASE STUDY OF IRUEKPEN-OZALLA ROAD AXIS. A RESEARCH PROJECT MATERIAL ON PHYSICS

A STUDY INTO ENERGY GAP IN SUPERCONDUCTORS. A RESEARCH PROJECT MATERIAL ON PHYSICS

ENERGY GAP
In solid state physics and related applied field, an “ENERGY GAP” also known as “BAND GAP” is the energy ranged in a solid where no electron state exist for insulators and semiconductors the band gap or energy gap, generally refers to the energy difference between the top of the valence band and the bottom of the conduction band, but in superconductors, the energy gap is the energy required to break up a pair of electron usually referred to as cooper pairs or simply put, the energy required to disrupt the state. Energy gap depend on temperature because of ‘thermal expansion’. (Emslay, J ; 1991). Energy gap also depend on pressure. Energy gap can further be divided into two groups, depending on the band structure, they are

1. Direct energy gap

2. Indirect energy gap Figure:

3.2 Energy Vs momentum for an indirect energy gap showing that an electron cannot shift from the lowest potential in the conduction to the highest potential in the valence band without a change in momentum. An indirect band gap means that the minimum energy in the conduction band is shifted by a vector relative to the valence band. The vector difference represents a difference in momentum. Recombination occurs with the mediation of a third body, such as a “phonon” or a crystallographic defect, which allows for conservation of momentum. This recombination will often release the band gap energy as phonons; instead of photons, and thus do not emit light.

3.2 HOW THE ENERGY GAP AROSE
The next big experimental discovery were done by two group. Goodman who was working on thermal conductivity and Brown Zemansky and Boorse who were making specific heat measurement. They discovered how and why the energy gap arose. Let us consider the way in which we build up the periodic table of elements. As one does this, one thinks of the orbits of an atom which one fills with electron. The unique chemical properties are associated with the extent to which one fills or empties an orbit. Here the electron can go only into certain orbits.

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A STUDY INTO ENERGY GAP IN SUPERCONDUCTORS. A RESEARCH PROJECT MATERIAL ON PHYSICS

OPTICAL AND STRUCTURAL PROPERTIES OF COPPER ALUMINUM DISELENIDE (CuAlSe2) COMPOUND THIN FILMS.A RESEARCH PROJECT MATERIAL ON PHYSICS

ABSTRACT

A low cost chemical bath deposition technique has been used for the preparation of Copper aluminum diselenide (CuAlSe2) thin films onto commercial microscope glass substrates. The values of deposition parameters were varied such as temperature (50-70oC), deposition time (12 – 60hrs), volume of complexing agent (1-9ml) and bath pH (8.35 – 10.10) to obtain good quality thin films. The optical, structural and morphological properties of thin films were studied by Jenway Software 6405 UV – VIS Spectrophotometer, X-ray minidiffractometer MD – 10 and Scanning Electron Microscopy (SEM) studies respectively. The optical property revealed that CuAlSe2 films have energy band gaps range value at room temperature and elevated temperature as 2.22 – 2.58eV and 2.00 – 2.14eV respectively. The X-ray diffraction study showed that the CuAlSe2 films were polycrystalline in nature with the preferential orientation along the (112) plane. The Scanning Electron Microscopy results indicated that the films were smooth, uniform and the substrate surface was covered completely at these experimental conditions.

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OPTICAL AND STRUCTURAL PROPERTIES OF COPPER ALUMINUM DISELENIDE (CuAlSe2) COMPOUND THIN FILMS. A RESEARCH PROJECT MATERIAL ON PHYSICS

THE DESIGN AND IMPLEMENTATION OF A FOUR-WAY TRAFFIC LIGHT CONTROL CIRCUIT

ABSTRACT

This work has been aimed at efficient means of controlling the traffic effectively for twenty-four hours. As the world is growing technologically more and more vehicles jump into the public road adding to the already existing number. Consequently, more efficient way of controlling the traffics becomes more desirable as compared to the obsolete way of using the traffic personnel’s. The design of this traffic light control is grouped basically into three; digital logic design, the power circuit and the power supply design. The digital logic design is based on integrated circuits which happens to be the modern way of designing digital systems, the power circuit design is aimed at lighting the different LEDS as and when due, while the power supply design strives to achieve a constant 8V dc supply for powering the circuit.For this work, the frame with the LEDS mounted on it has been constructed, the driven circuit was implemented and the entire system enclosed in the smoothened frame. The realized work was tested and guaranteed to give a firmly good level of performance.

CHAPTER ONE

INTRODUCTION

In the ever fast-growing world of business and technology today, there has become an increasing column of vehicles on every road in different place of the world. Traffic control light has become a very effective tool for sequential control of the teaming number of vehicles on the road to avert what would have been a recurrent saga of ghastly accidents at the junctions. There have been many ways of achieving this, uppermost among these being the employment of electronic monitoring circuits that which is controlled by presto clock. In developed countries, the employment of traffic personnels who would be jumped up and down at the centres of the junction just for the motorists to acknowledge their rigorous signs has long come of age. In developing countries where 24 hours traffic flow is involved, many societies are adopting the usage of the traffic light control. The advantage offered by this method of traffic control cannot be over emphasized. For one, it offers a more advanced technology that is less prone to miscalculation and its regrettable occurrence. They stand out better at night, then offer illumination to the immediate surroundings which become important for security purpose and in general add to there entire aesthetic beauty of night life.

The technology behind the design may vary from place to place, but the fact remains that in all cases an electronic (logic) circuit is made to control a power circuit. The electronic logic circuit is normally composed of the basic digital components of electronic design which includes oscillators, timers, counters, decoders, microprocessors, etcetera, while the power circuit includes the lamps and the drivers circuits. The digital circuit is designed to give an output commensurate to the design choice. The power supply unit is designed to generate a steady supply voltage which is used to power the logic circuit.

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THE DESIGN AND IMPLEMENTATION OF A FOUR-WAY TRAFFIC LIGHT CONTROL CIRCUIT

CONSTRUCTION OF REGULATED POWER SUPPLY SYSTEM (30V)

ABSTRACT

Regulated power supply is an electronic circuit that is designed to provide a constant DC voltage of predetermined value across load terminals irrespective of AC mains fluctuations or load variations. 30Volt regulated power supply is produced in this research work, the major component of the regulated power supply are 15V transformer, Diode, regulator and output cord. The constructed regulator can regulate AC power supply from 230V main down to 30Volt DC supply.

CHAPTER ONE

1.0 INTRODUCTION

A power supply is a device that supplies electric power to an electrical load. The term is most commonly applied to electric power converters that converts one form of electrical energy to another, though it may also refer to devices that convert another form of energy either mechanical, solar or chemical to electrical energy. A regulated power supply is the one that controls the output voltage or current to a specific value, the controlled value is held nearly constant despite variations in either load current or the voltage supplied by the power supply energy source (John et al, 2002).

Every power supply most obtain the energy it supplies to its load, as well as any energy it consumes while performing that tasks from an energy source. Depending on it’s design, a power supply may obtain energy from electrical energy transmission system, common example of this include power supplies that convert AC line voltage to DC voltage, energy storage devices such as batteries and fuel cells. Electromechanical systems such as generators and alternators, and solar power (Paul, 2006).

Regulator power supply is an electronic circuit that is designed to provide a constant DC voltage of pre-determined value across load terminals irrespective of AC mains fluctuations or load variations. A regulated power supply converts unregulated AC into constant DC with the help of a rectifier. It converts AC supply into DC supply. The function of a regulated power supply is to supply a stable voltage to a circuit or device that must be operated within certain power supply limits. The output from the regulated power supply may be alternating or unidirectional, but it is nearly always DC (Direct current) (Abbel,2004).

The type of stabilization used may be restricted to ensuring that the output remains within certain limits under various load conditions, or it may also include compensation for variations in its own supply source (Mark et al ., 200 6)

With the rapid growth of highly developed technology of instant communication, computerization, industrial automation and space exploration, the feats would not have been possible without the advent of electrical / electronics engineering. In electrical and telecommunication engineering field, systems and equipments like amplifiers, satellites, microwave link systems to name but a few depend for their correct operations upon the availability of stable well regulated d.c. power supplies. In experimental laboratories, the use of well regulated d.c. power supplies becomes inevitable because the result of these experiment depends largely on the quality power supply used.

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CONSTRUCTION OF REGULATED POWER SUPPLY SYSTEM (30V)

DESIGN AND CONSTRUCTION OF A 60AMP THREE PHASE AUTOMATIC CHANGE OVER SWITCH

ABSTRACT

The design and construction of a 60A, 3-Ф automatic power changeover from public utility supply to generator and vice versa was aimed at providing a useful system for use in our homes or offices. The system was achieved with a 66A 3-Ф contactor, 100mA transformers and relays. The system turns on a generator when the public utility (PHCN) is off by cranking the starter and a provision was made to stop cranking when the generator is fully started. A delay was provided to stop the generator five minutes after the PHCN is restored to avoid unnecessary off and on. A display that shows when PHCN or GEN is on was provided.

This project work deals on the design and construction of an automatic power changeover that will change/transfer control from MAINS to Gen set and can switch ON/OFF the Gen automatically. The system integrates phase selector in MAINS and changeover to Gen. It is designed in several blocks all combined to from one functional unit. A +5v regulated DC power supply unit forms the first block whose output is fed to priority encoder and decoder block. The output of the BCD – Decimal decoder is used to select the phase in priority through a transistor driver stage and electromagnetic relay that activates contactors.

CHAPTER ONE

INTRODUCTION

Industrial automation and control has contributed immensely to the high rate of the world’s technological growth. Power control and automation is a part of this field which is applied in virtually anywhere electrical power is used, generated or transmitted. Manual power change-over switches have been in existence and in different forms and shapes. 1959, the advent of microelectronics has paved way to modify the manually operated change-over switches. This project deals with the design and construction of automatic change-over switch with indicator. It eliminates the time and energy spent in operating the manual change – over and starting of Gen. Set. It is fully automated. It can be used in residential houses, offices and most importantly, in factories that required constant power supply. It has so many advantages over the existing ones/types.

1.1. BACKGROUND OF THE STUDY

This project work is embarked upon to eliminate nearly every shortcomings associated with the manually operated type to ensuring that it is fully automated. This system is realized in several functional blocks all combined to form one functional system. The first block is a 3-phase MAINS regulated dc power supply unit that powers the overall circuit and acts as the input. The output of thin block is fed into a priority encoder (74147) which selects the most prioritized phase at a time. The third block is a BCD – to – DECIMAL Decoder (7442) used to decode the prioritized phase.

The fourth is the driver stage which comprises of NPN transistor that energizes the electromagnetic relay which switches the phase in priority. The Gen set switching section is achieved using the least prioritized phase. This section switches ON the Gen set when all the NEPA phases are low, OFF or faulty. Once the Gen set phase is selected, a switching transistor fires an SCR which conducts large battering current to the ignition coil of the Gen set. Panel indicators are used to show the status of the system.

1.2. OBJECTIVES OF THE PROJECT

The major objectives of this project is to design and construct an automatic change-over switch with Gen set switching facility capable of transferring control from MAINS to Gen set.

It is also aimed at equipping the graduating student with Hands – on experiences which is invaluable in their professional practice. It is aimed at grounding the graduate of EEE in electronic system designs involving power control and automation using random/Hard wired logic. Another objective of this project is to acquaint the graduating students on the ethics of Engineering, technical and scientific writing which is a nucleus of engineering professional practice.