1.0 Introduction
1.1 Background Of The Study
The quest to convert D.C. power to A.C power to run some essential appliances results due to erratic power supply being experience. Although, between the 19th century to mid 20th century, D.C. to AC power conversion was accomplished using rotary converters or motor generator set (M-G set).
In early 20th century, vacuum tubes and gas filled tubes began to be used as switches in inverter circuit. In contrast the early A.C. to D.C. converters used an induction or synchronous a.c motor directly connected to a generator (dynomo) so that the generator's commutator reverses its connections at exactly the right moments to produce D.C.
Considering the above reasons, for the study, many electrical equipments have either developed a problem or even stopped working entirely. As a result, many businesses have been crippled thereby affecting the economy as a whole with respect to Nigeria.
Again, power disturbances occurrence are on increase resulting to high voltage spikes and momentary voltage drops, this often affect the performance of sensitive electrical electronics equipment.
Unincessant supply of electric power can not be over emphasized in Nigeria presently, this has become the order of the day and many Nigerians now presume power outages as a normal routine in the power sector. There are factors responsible for this ugly situation such as natural disasters, vandalism, maintainability, sustainability, inadequacy and lack of vision by the political leaders to invest adequately in power sector, also absence of replacement policy resulting in absolute abandon of electrical equipment or project, unsustainable human capacity and inadequate and remuneration system to motivate human resources term to perform well on their course.
The progress made some decades ago in developing alternate source of energy has proved that independent power system are not only possible but as well practical. A wide variety of generating equipment is now available to allow individuals take advantage of any prefer renewable resources of energy. Most of these systems produce only direct current (DC) for a number of reasons and at low voltages. However, it is well known that the alternating current is the greatest and most useful form of current being generated by the power grid due to its advantages over direct current. Thus, most of the appliances and equipment are built using a.c. input source.
Therefore, there arises the need for converting direct current (DC) to an alternating current (A.C.) having a constant frequency. This process is known as inverting.
1.2 Aim and Objectives Of The Project
The aim of this project is to design and construct a circuit that will take a 24V dc input from battery and produce a 200VA (AC) output at 200V – 220V, 50Hz with under voltage and over voltage protection. The study intends:
- To design an electrical system that converts d.c. power to a.c. power to drive various appliances used in the laboratories, theatres, rural areas etc.
- To have a source of generating electricity that has no negative effect on the environment (i.e. no greenhouse effect).
- To provide an exposition to the HND students to simple electrical design, analysis and building of circuits.
- To provide a noiseless and weightless source of electricity generation.
- The study will also serve as a means of impacting practical knowledge and skills to students, lecturers and other who may wish to acquaint themselves with the principles of operation of an inverter system.
1.3 The Scope Of Study
The scope of this study is to design and construct of an inverter system with an output power rating of 2KVA, maximum output current rating of 9.09A, and output voltage of 200V a.c. at 50Hz from a 24V dc input. A few most widely used applications of inverter include running of computers, microwaves and electrical power tools etc.
The scope of this project shows how low voltage d.c power supply is used to energized an inverter circuit. It also show how low a.c. voltage obtain from the oscillator output is being amplified and step up to a required output voltage.
1.4 Limitation Of The Study
In spite of the construction of an inverter and its noiseless and pollution free nature unlike other alternative sources of the generating electricity, there is a need for charging and recharging the battery from time to time.
The inability of the circuit to provide a pure sine wave output from gives room for further improvement. This is because it is quite expensive to design a pure wave inverter circuit.
Again, lack of financial assistance incapacitated the project to achieve its accuracy and reliability as well its appearance (packaging).
1.5 Definition Of Terms
Since the inverter system is an electrical/electronics system, current will flow through the various components, voltage will be dropped at some points, and therefore, the following principles were applied in designing the project.
1.5.1 Joule's Law
Joule has two laws Viz:
Joule's first law shows the relationship between heat produced by an electric current flowing through a conductor. That is the rate of heat generated (p) in a metallic conductor is directly proportional to the square of the current (I) flowing through the conductor provided that temperature is held constant
Q a I2 _____ (1)
Q = I2R _____ (2)
Q = I2Rt _____ (3)
Where Q is the amount of heat in joule, I is the electric current flowing through a conductor in ampere, R is the amount of electric resistance present in the conductor in ohm and t is the amount of time it occurs in second.
Joule's second law: States that internal energy of a gas does not change if volume and pressure change but does change if temperature changes.
1.5.2 Ampere's Law
This relates the integrated magnetic field around a closed loop to the electric current passing through the loop. Thus for any closed loop path, the sum of the length element times the magnetic field in the direction of the length element is equal to the permeability times the electric current enclosed in the loop.
1.5.3 Faraday's Law of Electromagnetic Induction
It states that whenever there is a change in magnetic flux linked with a circuit, an emf is always induced in it and the magnitude of the induced emf is equal to rate of change of flux linkage.
e.m.f generated =
1.5.4 Lenz Law
When an emf is generated by a change in magnetic flux according to Faraday's law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it.
The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant.
1.5.5 Ohm's Law
This states that the ratio of potential difference (V) between any two points in a circuit is directly proportional to the current (I) flowing through them, provided temperature and other physical materials remain constant.
V = IR
I = V/R
R = V/I
1.5.6 Kirchoff's Voltage Law
This states that the algebraic sum of voltage in each of the conductors in any closed path in a network is equal to the algebraic sum of emf
1.5.7 Kirchoff's Current Law
This states that the algebraic sum of currents in a network of conductors meeting at a point is zero. i.e. At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node.
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