| Content | ABSTRACT
Uninterruptible power supplies UPS are used to provide power when regular utility power is unavailable. Although they are commonly used for providing power in remote locations or emergencies, this is not because they are the same as auxiliary power units, emergency power units or standby generators. Unlike the aforementioned power sources, UPS provides an immediate and continuous supply of power to a device, hence protecting it from power interruption and allowing time for auxiliary or emergency powers, to kick in equipment to be safely shut down or utility power restored. The major aim of this was to design a system which will be able to convert a UPS system to a sine wave inverter. The sine wave inverter unlike the UPS provides a delay when power outage occurs. This delay in supply is acceptable for loads like lightening points, fans etc. but completely unacceptable for sensitive equipment like computers and printers. This delay may cause loss of data.
CHAPTER ONE
1.0INTRODUCTION
The most recent advancement in technology has really given birth to different development in the field of engineering. Provision has been made by technologist who covers a wide range of humans environment, given solution to humans problems.
In the recent times, power supply has been epileptic in the country which has really affected consistent power source. Many power systems were found to be able to maintain power supply to the load during mains failure PHCN. Most of these loads were designed so that electrical supply to them should be maintained without interruption. Electricity can be generated by devices to convert some readily available sources of energy since electricity generation can be interrupted at any time as a result of fault and all electronic devices need an alternating current , the use of an inverter to utilize an alternative source of energy becomes so necessary.
An inverter is an electronic device which converts DC energy to AC energy. Thus, the technological breakthrough resulting to the production of this system has encouraged the optimum utilization of computers and related equipment's. The beauty of inverter system is the fact that it accepts all the power anomalies, conditions and filters properly the public power supply output to most load which require pure grade sinusoidal voltage rated output. They are used in a wide variety of applications such as the complicated electronic systems of orbiting satellite and cool astronaut suites. Inverters are also used to operate gyroscope and other air borne instruments. Due to low voltage power sources such as solar cells, nuclear cells, and fuel cells, inverters has become increased in demand.
The system is unaffected by variation in the mains supply and during the period of power failure will continue to supply to the load for a specified duration. Modern DC to AC inverters is reliable and requires less maintenance
DC and AC Current
In the world today there are currently two forms of electrical transmission, Direct Current DC and Alternating Current AC, each with its own advantages and disadvantages. DC power is simply the application of a steady constant voltage across a circuit resulting in a constant current. A battery is the most common source of DC transmission as current flows from one end of a circuit to the other. Most digital circuitry today is run off of DC power as it carries the ability to provide either a constant high or constant low voltage, enabling digital logic to process code executions. Historically, electricity was first commercially transmitted by Thomas Edison, and was a DC power line. However, this electricity was low voltage, due to the inability to step up DC voltage at the time, and thus it was not capable of transmitting power over long distances.
V IR
PIV I2R
As can be seen in the equations above, power loss can be derived from the electrical current squared and the resistance of a transmission line. When the voltage is increased, the current decreases and concurrently the power loss decreases exponentially; therefore high voltage transmission reduces power loss. For this reasoning electricity was generated at power stations and delivered to homes and businesses through AC power. Alternating current, unlike DC, oscillates between two voltage values at a specified frequency, and its ever changing current and voltage makes it easy to step up or down the voltage. For high voltage and long distance transmission situations, all that is needed to step up or down the voltage of the transformer. Developed in 1886 by William Stanley Jr., the transformer made long distance electrical transmission using AC power possible.
Electrical transmission has therefore been mainly based upon AC power, supplying most Nigerian homes with a 220 volt AC source. It should be noted that since 1954 there have been many high voltage DC transmission systems implemented around the globe with the advent of DC/DC converters, allowing the easy stepping up and down of DC voltages. Like DC power, there exist many devices such as power tools, radios and TVs that run off of AC power.
It is therefore crucial that both forms of electricity transmission exist; the world cannot be powered with one simple form. It then becomes a vital matter for there to exist easy ways to transform DC to AC power and vice versa in an efficient manner. Without this ability people will be restricted to what electronic devices they use depending on the electricity source available. Electrical AC/DC converters and DC/AC inverters allow people this freedom in transferring electrical power between the two.
Offline / standby | CHAPTER ONE
1.0. INTRODUCTION:
A DC to AC inverter is a simple device that produces an AC output from DC supply. The technique which is used in the realization of the inverter is chosen for simplicity and efficiency basis.
The input is DC supply unit from 12V battery which is used to power the system. The triggering unit triggers the ON/OFF of the silicon control rectifier SCR thyristor component of the inverter. The output of the inverter which is a high voltage AC is in form of a square wave.
Therefore, to get sine wave, the AC output is fed to the filter unit to filter off the harmonics. The filter provides a sine wave from the square wave output of the transformer this system enables the user to obtain an unimpeded power supply from two different sources, one source from the mains.
1.1. PURPOSE OF THE STUDY:
The purpose of carrying out this research work includes the following:
1. To highlight the aim and the necessities of DC to AC inverter in modern technology.
2. It is important to our homes where there is no electricity of which equipment can be powered by inverter using 12V battery heavy duty.
3. It is used in renewable energy technology i.e. solar bio mass etc.
1.2. SCOPE OF THE STUDY:
The inverter could be used in a car or boat to power device such as laptops, videogames, television or DVD player.
DC to AC inverter has the step of effecting the flow of air into an inverter honing and exhausting at least of the air through the metal core at a power transformer. It also improves the structure of cooling itself and increase power output comprising an enclosure with cooling air inlet aperture and also inverting DC to AC electricity.
1.3. BLOCK DIAGRAM OF THE INVERTER:
Fig. 1.1 Block Diagram of the Inverter
1.3.1.THE RELAY CIRCUIT OVER DISCHARGE SECURITY:
The relay circuit performs a vital role in the system as an over discharge security whereby whenever the battery terminal voltage drops to 1.8V percent, the relay switches off and automatically switches off power supply to the main oscillator or inverter circuit.
1.3.2.THE OSCILLATOR:
The oscillator is designed with a 4047 IC particularly designed for oscillation. The 4047 IC has 14 pins, pin 1, 2, 3 are connected to the frequency determinant components which are resistors and a capacitor. Pin 10 and 11 are the output pins which go high and low at different time intervals so that AC pulse can be obtained.
1.3.3.THE BUFFER CIRCUIT:
The buffer is made up of a transistor for each output; the buffer isolates the power MOSFET arrangement from the oscillator. The MOSFET are arranged into different pairs 3 MOSFETS for each and each MOSFET rates about 30 amps.
1.3.4.TRANSFORMER:
The transformer is a stepup one and the primary is centre taped of 12012 volts turns and secondary is 240 volts. The transformed output pulse is controlled by the pulse which is controlled by the MOSFETs and by the oscillator frequency.
1.4. PRINCIPLES OF OPERATION:
Inverter is the conversion of DC power to AC power at a symmetric AC output voltage of desired magnitude and frequency. It involves the connection of the D to AC circuit through switching devices which are turned on and off for appropriate periods relative to the DC or Ac power. Opening and closing of the switching device Diodes and thyristors is affected wholly in uncontrolled rectification or partly in controlled rectification by the AC supply voltage through the process called Natural communication which is the transfer of current from one branch of circuit to another in the case of AC supply voltage change polarity. This natural communication process can be applied to inversion when feeding power from DC source into relatively large AC power system. In the second approach, a means is provided which enables the current flowing in the switching device to commutate at any instant determined these two approached load to distinct classes of static inverters namely;
I. Current fed inverter.
II. Voltage fed inverter.
CURRENT FED INVERTER: This is an inverter in which supply current cannot change quickly. It is achieved by series DC supply inductance which prevents sudden change in current. The load current magnitude is controlled by varying the input DC voltage to large inductance.
VOLTAGE FED INVERTER: The DC supply voltage is essentially constant and dependent on load currently drawn, the inverter specifies by load. It is used for uninterrupted power supply UPS. | ABSTRACT
The aim of this project is to design and implement a single phase inverter which can convert DC voltage to AC voltage at high efficiency and low cost. Solar and wind powered electricity generation are being favored nowadays as the world increasingly focuses on environmental concerns. Power inverters, which convert solarcell DC into domesticuse AC, are one of the key technologies for delivering efficient AC power. A low voltage DC source is inverted into a high voltage AC source in a twostep process. First the DC voltage is stepped up using a boost converter to a much higher voltage. This high voltage DC source is then transformed into an AC signal using pulse width modulation. Another method involves first transforming the DC source to AC at low voltage levels and then stepping up the AC signal using a transformer. A transformer however is less efficient and adds to the overall size and cost of a system. Therefor the former method is the one used to implement this project.
To deliver such performance, the power inverters is driven by highperformance PIC 16F877A microcontroller units MCUs that can achieve highlevel inverter control, and therefor this microcontroller is the heart of the system and controls entire system. The microcontroller is programmed using embedded c compiler and in specific mikroC pro to generate sine pulse width modulated SPWM pulses which are used to drive Hbridge. By alternate switching switches of two legs of Hbridge alternating 340V DC voltage is converted into 240V Ac voltage.
The design is essentially focused upon low power electronic appliances such as personal computers, chargers, television sets. To build the design it is first mathematically modeled then is simulated in Proteus and finally the results are practically verified. |
TABLE OF CONTENT
Title Page
Approval Page
Dedication
Acknowledgement
Abstract
CHAPTER ONE
The Problem and its Setting
Introduction
Statement of Problem Definition
Sub Problem Definition
Hypothesis
Limitations
Delimitation
Definition of Terms
Need For The Study
Assumptions
Organization
CHAPTER TWO
11: Review of Relation Literature
Introduction
Science Roles
Artificial Intelligent
Simulation
CHAPTER THREE
111: Designation of The Study
Introduction
Components
Procedures For The Design
Circuit For The Design
Flowchart For The Design
CHAPTER FOUR
Iv: Presentation And Analysis of The Design
Introduction
The Software Requirement
Detail Analysis of The Design
System Description
General Analysis
CHAPTER FIVE
V: Summary
Conclusion
Recommendation
Bibliography
Appendices
| CHAPTER ONE
INTRODUCTION
1.1 Background of the study
A battery charger is a device used to introduce energy into a secondary cell or rechargeable battery by forcing an electric current through it. The charging protocol depends on the size and type of the battery being charged. Some battery have high tolerance for recharged by connection to a constant voltage source or a constant current source; simple chargers of this type require manual disconnection at the end of the charge cycle, or may have a timer to cut off charging current at a fixed time. Other battery types cannot withstand long highrate overcharging, the charger may have temperature or voltage sensing circuits and a microprocessor controller to adjust the charging current, and cut off at the end of charge.
A tackle charger provides a relatively small amount of current, only enough to counteract selfdischarge of a battery that is idle for a long time. Slow battery chargers may take several hours to complete a charge, highrate chargers may restore most capacity within minutes or less than an hour, but generally require monitoring of the battery to protect it from overcharge Emerson, 1998.
A battery, which is actually an electric cell, is a device that produces electricity from a chemical reaction. In one cell battery, a negative electrode; an electrolyte, which conducts ions; a separator, also an ion conductor; and a positive electrode. an electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technical improved Daniell Cell in 1936, batteries have become a common power source for many household and industrial applications Emerson 1998.
There are two types of batteries: Primary Batteries disposable batteries, which are designed to be used once and discarded, and Secondary Batteries rechargeable batteries, which are designed to be recharged and used multiple times. Battery comes in many size, from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers and inverters.
However, in recent times, battery charger has become very useful and popular to DC equipment. Most of the electronic devices such as laptops, mobile phone, etc., and mobile machines like vehicle and motorcycles operational capacity depend on the DC power supply from a battery.
1.2 Scope of the study
This project work is limited to the construction and demonstration of a simple battery charger of 12volts. The circuit input voltage is 240volts from the A.C supply mains which will be stepped down by a stepdown transformer to 12volts. The 12volts A.C is rectified through a bridge rectifier and filtered through capacitor connected in parallel from the positive terminal of the bridge rectifier. The output voltage is used to charge a battery.
1.3 Statement of the problem
A simple 12volts charger works by supplying a constant DC or pulsed DC power source to a battery being charged. The simple charger does not alter its output based on time or the charge on the battery. This simplicity means that a simple charger is inexpensive. The circuit of a battery charger has the ability to convert voltages from one form to another usually AC to DC voltages. This process is carried out through the use of some important components like: rectifiers, capacitor to filter and remove ripples from the AC source and a voltage regulator IC. However, this project is based on the construction of a 12volts simple battery charger with local materials to reduce cost.
1.4 Purpose of the study
The purpose of this project work is to design construct and demonstrate how a simple 12volts battery charger works.
1.5 Significance of the study
A simple 12 volt battery charger is a simple circuit that comprises of different component that are soldered together on a circuit board to give or produce a require function. Therefore, the importance of this project work is to aid both technicians and students on how to construct a simple battery charger circuit and how it works.it is hoped that after the construction of this charger circuit, it will be kept on the laboratory to be used for battery charging and for practical's and other academic functions.
1.6 Limitation
During the project work, the researcher encountered the following problems which in one way or the other have prevented him from completing the work at the usually time. These include: financial problems, time factor and unavailability of material which the researcher have to move from far distance area in search of textbooks and other important materials. |
1.1.BACKGROUND OF THE STUDY
According to W. Stephen Woodward W. Stephen Woodward Jan 22, 2001, explicit airflow detection is essential in many applications. High powerdensity electronics are liable to overheat and selfdestruct when coolingfan failures go unnoticed. Heating and airconditioning systems often incorporate multipoint monitoring of ventilationduct flow. Cleanroom airhandling systems with undetected dirty, blocked air filters can ruin process yield. Laboratory fume hoods can contain volatile solvents or toxic reagents, making adequate air turnover critical to safety. In these and similar scenarios, the consequences of undetected airflow interruption can range from the merely expensive to the frankly dangerous. Therefore, it becomes necessary to use some reliable means for airflow detection. Usually, either a mechanical pressureactuated vane switch or one of the various
types of heattransferbased airflow sensors is employed.
An advantage of the method of air sensors used here is that they contain no moving parts. But they often require several watts of heating input to run hot enough to overcome ambient temperature variations. The detector described here is a powerthrifty member of the thermal genre. It employs an ambientcompensated airflowdetection scheme based on differential heating of a series
connected transistor pair. In operation, 200mV reference regulator A1 maintains a constant Q1/Q2 current drive equal to 40 mA i.e., 200 mV/R1. Since the two transistors pass the same current, their relative power dissipations are determined solely by their respective V voltages. For the circuit constants shown, these power levels work out to
4 V 40 mA 160 mW for Q1 and 0.75 V 40 mA
30 mW for Q2. The 130mW heatflow difference leads to a temperature difference determined by the heatdissipationversusairspeed characteristics of the 2N4401s plastic TO92 package. The TO92s thermal impedanceversusairspeed characteristic is well approximated by the simple equation shown below
Z Z 1/S K A
Where:
Z total immersion junctiontocase thermal
Impedance 44C/W
S stillair casetoambient conductivity 6.4 mW/C
K Kings Law thermal diffusion constant 750 W/Cfpm
A airspeed in ft. /min.
Therefore, the Q1/Q2 temperature differential ranges from 130 mW 200C/W 26C at 0 fpm zero flow, to 130 mW 75C/W 10C at 1200 fpm the 14mph breeze found at the output face of a typical 100cfm cooling fan. This flowdependent temperature differential gives rise to a flowdependent V differential via the 2N4401s typicaltransistor V temperature coefficient of 2 mV/C. Comparator A2 matches this Q1 /Q2 ratio to R2/R3. Under high airflow, Q1 is cool and Q1 /Q2 > R2/R3, which makes A2s output high i.e., flow OK. With a stagnant airflow as might connote fan failure, flue fouling, or filter fillup Q1 is allowed to heat up, driving Q1 /Q2 < R2/R3. This causes A2s output to slew low, asserting the lowflow faultalarm condition. For these circuit constants, the noflow alarm threshold is 100 fpm Fig. 1, again. But this line in the sand can be easily adjusted. Raising Q1s power dissipation by boosting collector current increases the threshold.
Setting R1 4 , for instance, would bump Q1s power input to 200 mW and quadruple the lowairspeed set point to 400 fpm. Increasing R1 allows the setpoint to be moved the other way toward a lower flow level.
For example, R1 6.4 would cool Q1 to a tepid 125mW and thereby quarter the nogo flow criteria to 25fpm.
Besides being adaptable to different flow rates, the circuit also can accept different supply voltages. In these cases, R1 must be multiplied by V 1/4 to hold
Q1s I V heating level constant.
1.2.STATEMENT OF PROBLEM:
Owing to the alarming rate of the ugly incidents caused by the unavailability of air detector, the following forms the statement of problem of this study
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