The Design and Construction of 2KVA Inverter
Chapter One
OBJECTIVE OF THE PROJECT
The purpose of this project is to design and construct a circuit that will take a 24V DC input from a 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 c. power to a.c. Power to drive various appliances used in 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 on 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 others who may wish to acquaint themselves with the principles of operation of an inverter system.
CHAPTER TWO
LITERATURE REVIEW
WHAT IS AN INVERTER?
An inverter is an electrical system that converts direct current (d.c) power into an alternating current (A.C.) power. The inverting process can be achieved with the help of some components such as transistors, resistors, tunnel diodes, zener diode, silicon controlled rectifier (SCR) etc. Thus, inverter can be found wherever there is a need to modify and sustain a.c. power in an establishment as regards to noiseless environment.
Inverters have become very important in modern technology because of the need to produce continuous supply of electric power to critical loads such as computers, surgical equipments, security doors, automatic teller machine (ATM), telecommunication and broadcast equipments etc. Inverter is a major segment of an uninterrupted power supply Unit (UPS). The inverter is in high demand because of the advantage it offers against other alternative ways of power generation such as generators.
The major disadvantage of the inverter is low power generation compared to generators. i.e 100watt – 5000watt as against 800watt-50000watt for generators.
In modern inverter circuits, the d.c power is connected to a transformer primary through the center tap of the primary winding. A switch is rapidly switched back and forth to allow current flow following two alternate paths through one end of the primary winding and then the other.
Inverters are classified based on factors such as input and output voltages, power rating and output waveforms. Considering the output waveform, they are square wave, modified sine wave and pure sine wave.
The square wave output is quite far from waveform available in the normal mains outlet and this cause problem on equipments such originally design with the sine wave signal. Sometime, most devices hardly operate with square wave like variable speed equipments.
The modified sine wave is the next step closer to the main sine wave. This has becomes popular in many applications as it is quite easy to achieve and inexpensive. This types of inverter generally uses a switch mode power supply that generates direct current (d.c) voltage power transistors. FETs modified sine wave is compatible with electronics but it may induce long mechanical buzzing.
The true sine wave inverters allow connected load equipments to operate in the same way as they would from mains supply. The only problem is that true sine wave inverters are very expensive compared to the modified and square sine wave inverters.
THEORETICAL FRAMEWORK
This focuses on having an understanding of the circuit components description used in the course of design and construction of this project. These components are resistor, capacitors, Diodes, Transistor, MOSFETS, transformer etc.
CHAPTER THREE
DESCRIPTION OF THE SYSTEM
Description of the building block of the system
The D.C. to A.C. inverter is made up of several building block as shown in the block diagram below.
The basic working principle of the inverter system. An inverter system is used to provide uninterrupted A.C. power supply to the load connected at its output socket.
Inverter system provides constant A.C. supply at its output socket, even when the A.V. mains is not available or available for more understanding, we shall consider the following:
- When the A.C. mains supply is available
- When the A.C. mains supply s not available (inverter) will operate on battery supply.
(i) When the A.C. mains supply is available when the A.C. mains supply, this A.C. main supply goes to the A.C. main sensor, Relay and battery charging section of the inverter.
A.C. sensor inform the relay about available of the A.C. mains supply. When this relay receives signal form the A.C.l mains sensor it will directly passes the A.C. mains signal to the output socket of the inverter. But before the relay could get signal form the A.C. main sensor, the sensor will first send signal to pin 10 of oscillator I.C for shunt down of the inverter from A.C. main operation.
During the operation of A.C. mains the battery charging section converts the A.C. mains to D.C. for charging of the inverter battery, with required voltage and current for normal charging.
When the A.C. mains supply is not available.
When the A.C. mains supply is not available an oscillator circuit inside the inverter generates 50Hz frequency mostfet drive signal.
CHAPTER FOUR
CONSTRUCTION, TESTING AND PACKAGING
CONSTRUCTION
Construction can be said electronically to be the process of putting together various components that make up a circuit or system to work perfectly. Construction of this project (inverter system) needs much to be designed especially when handling some of the components in the circuit and also the arrangement of the MOSFETs and transformer winding. The first stage of the construction was to obtain a very good efficient and functional circuit diagram, meanwhile certain features were included to make the system meet up with the specification.
After obtaining a good circuit diagram which was simulated, the necessary components were purchased from the market. Each of the components was tested to ensure good condition of it before using in the construction.
CHAPTER FIVE
BILL OF ENGINEERING MEASUREMENT AND EVALUATION (BEME)
Components used were locally sourced and purchased for Ogbete main market, Kanyeta market and Coal camp market.
CHAPTER SIX
SUMMARY
It is believed that the construction of 2KVA inverter has been done successfully. Considering the features compose in this system such as the oscillator, drivers, amplifiers and transformer stages have been taken time to design in order to achieve its set objectives. Thus, the objectives of this design and construction work is to invert D.C (direct current) energy into an A.C (altemating current) energy at 200-22OV by frequency of 50H3.
Due to difficulty and expensive cost in designing a pure since wave, the oscillator produce an a.c output modified sine wave signal within the range of 1.5-7.0v which is adjustable at 50H3 frequency. This result to the ability of the oscillator to switch at interval.
However, with the help of the drivers and amplifier, the transformer could receive signal for proper increase to a set value usually 22OV.
Without doubt, the set objectives of this design and construction work have been achieved because the inverter system can successfully convert a 24Vdc source from a battery into a 200-220V a.c sinusoidal voltage.
CONCLUSION
Stable power supply is very essential to all walks of life because power supply is the blood that flows through every sector and sustain it to achieve its aims. Among other alternate sources of power supply, the inverter system has proved reliable, efficient and economic wise in some of the aspect of electrical appliances. Finally, this design and construction of 2KVA inverter system achieved its aim with high efficiency and reliable though, there accumulates some limitations prone to it compare with commercial inverters. It has been tested and seen to be good enough for domestic use with respect to its maximum load requirement. With a 24V/75Ah d.c battery, the inverter could last for more than 8 hours if properly loaded.
RECOMMENDATION
The oscillating section of this project produces a modified sine wave which can be improved by designing the oscillator section with some additional components to give a pure sine wave form as regards to national grid generation sine wave but at a higher cost.
Also, this system can be improved by increasing the number of MOSFETS which determines the amperage of the system and lead to greater efficiency.
Again, the transformer capacity should be affected by increasing its numbers of primary and secondary windings.
The inverter should not be loaded to its fully capacity as this could damage incase of slight loading increment. Rather, a tolerance should be provided at about 14% which helps to accommodate some systems that require heavy starting current and less current while running.
Moreover, I recommend that the system should be load with a non-resistive appliances in order to take power factor of such appliance into cognizance instead of a pure resistive load. This tends to boost its efficiency.
A battery with higher amperages should be used because it constitutes for a last longer period for the system to function.
PROBLEM ENCOUNTERED
During the course of this project a lot of challenges were met such as:
The unavailability of some components in the markets traded.
Designing of a voltage monitor circuit and its delay timing circuit.
We had challenges in connecting the components especially, the oscillator and the MOSFETS cause they are sensitive to touch but rugged when connected in the circuit.
Finally, we had difficulty in sourcing other relevant materials towards this project and the cost of acquiring them. Though, we were able to rectify all these as we can.
REFERENCE
- Edward Hughes (7th education) Electrical Technology
- Horsey, M.P, (1988) Electronics in practical, Basil Blackwell, Great Britain.
- Maddock R.J.C Calcutt (1988) Electronics: A course for Engineers, John Wiley and son, Inc, Hong Kong.
- Meadon R.G (1978), Technical Electronics 2, Macmilan Publishing company Inc London.
- Theraja B.C and Theraja A.K (2006) Electrical Technology, S. Chand and company ltd, Head Office: 7361 RAM, Nagar, New Delin, India.
- Sinclair L.R (1990) Practical Electronics Hand Book, second edition, Heineman Newness, Great Britain.
- Samuel D.A (1989) Success in Electronics, Scan Publishers, Washington D.C U.S.A.
