DESIGN AND CONSTRUCTION OF 2KILOWATTS POWER INVERTER FOR FARM HOUSE USE
BY
OLALUSI, Oluwaseyi Gabriel (AGE / 03 /1304)
FEDERAL UNIVERSITY OF TECHNOLOGY AKURE
FEBRUARY, 2010
DESIGN AND CONSTRUCTION OF 2000WATTS POWER INVERTER FOR FARM HOUSE USE
BY
OLALUSI, OLUWASEYI GABRIEL (AGE / 03 /1304)
A Project in the Department of Agricultural Engineering submitted to the School of Post Graduate Studies in partial fulfillment of the requirement for the award of Post Graduate Diploma (PGD) in Agricultural Engineering.
FEDERAL UNIVERSITY OF TECHNOLOGY AKURE
FEBRUARY, 2010 ii
CERTIFICATION This is to certify that that this work was carried out by Mr. Olalusi Oluwaseyi Gabriel with matriculation number AGE/03/1304 in the department of Agricultural Engineering in the school of Engineering and Engineering Technology, Federal University of Technology Akure, Ondo State, Nigeria. In partial fulfillment of the requirement for the award of Post Graduate Diploma (PGD Eng) in Agricultural Engineering of the Federal University of Technology Akure, Ondo State, Nigeria. This work has not been submitted elsewhere for the award of any other degree or diploma.
……………………………. Dr F. R. Falayi
………………………………… Date
Project Supervisor
………………………………
…………………………………
Prof. L. A. S. Agbetoye
Date
HOD
iii
DEDICATION This project work is dedicated to my late mother
Mrs Elizabeth Adekunbi Olalusi (A’yinke – Ade) Nee Fowowe
Died on 17th March, 2006 Aged 57years And To all women who suffer daily from domestic violence in the world
iv
ACKNOWLEDGEMENT I owed it all to the Almighty God for His mercies, protection, provision and strength for the successful completion of my Post Graduate Diploma Programme, I am forever grateful. I gratefully acknowledged my Project supervisor, Dr F. R. Falayi, for his patience, moral support; encouragement and advice, in making this project a reality. Also to my students and friends of mine Ajetomobi Muyiwa and Lekan Omoniyi, for their creativity minds and encouragement, in making the project a reality. My prayer is that God in His infinity mercy will amply bless them. I will remain ever grateful to my lovely late mother, Princess E. A. Olalusi, for the support she gave me during her short time on earth. May her soul spirit rest in peace, amen. To my siblings, Sister Dele, Wale, Foluso, Funbi, and Busayo, I say thank you for your support and encouragement, I am very grateful. Also to my little girls, Seyi and Sola, God bless you amen. To my PGD colleagues, Mr. Esho Kola, Mr. Ajayi ‘Dipo, Mrs Ebietomiye, Mrs Helen Adefioye, Mr. Faniyi Victor, Mr. Olayemi, Mr. Felix Osu, Mr. Abe, Mr. Ahmed, Mr. Mayaki, Mr. Lasisi; I say God bless you all amen. And Mr. Godwin Aduku Ukwenya, whose encouragement and persuasion help me to complete this project. My sincere appreciation goes to entire management, staff and students of Don Bosco Technical Institute of Electrical Engineering and Maintenance for their supports. It was there that I conceived this technological idea which has made many of their students to be self-reliance. To Rev. Fathers Stephen Omoniyi and Joe Gyamfi, God will increase you more and sustain you in His vineyard, amen. To Mr. Apotiade, Mrs Adeuyi B., Gbenga Bambe and Mr. Abiodun Abimbola, I say thank you for moral and financial supports. A big thanks to my father, Mr. Olalusi, M. I. for his support, may he live long to reap the fruits of his labour, amen. Finally, special encomium to my love and angel; Mofifoluwaso, “there is nothing better than the encouragement of a good friend”. I will always love you.
v
ABSTRACT The importance of electricity to farm techniques in the present day cannot be over emphasized. Hence, 2Kilowatts power inverter was designed, constructed and tested. The project is about power supplies and conversion from one form to another i. e. Direct Current to Alternating Current. This is to deal with the erratic power supply to rural area and improve social well being of rural people, and salvage the urban-drift and make farming business attractive and interesting. The methodology used to achieve the objectives focused on the design of transformer as the main integral part of the inverter. The design and selection of other components were based on their availability, durability, affordability, thermal and electrical properties. The inverter was designed, developed and tested. It is 12-pulse inverter i.e. consist of 12 IRFP 260N FETS transistors to supply electric power similar to the power grid of sinusoidal waveform. The evaluation of the inverter was carried out in the electrical workshop of Don Bosco Technical institute of Electrical Engineering and Maintenance, Akure. The results obtained show that the inverter has nominal AC output Voltage is 220Vac; Ac operating voltage Range from 220 – 240Vac; Nominal AC Frequency is at 49.5Hz ; Maximum AC output Current is 9.2Aac as against 9.91Aac calculated; maximum AC output Power is 2,024Watts as against 2,181Watts designed for. It has 93% efficiency. It was tested as independent unit of power supply with forgo lead-acid battery product of 12V, 200Amperes Hour against idling; non-compressive and compressive loads. From the graphic analyses, it shows that the inverter consumed little battery energy when no load is applied; while on non-compressive loads, it consumed 54.8% of the total battery charges within 4hours of test period. 63.6% of the battery energy was consumed when on compressive loads for 3hours test period. This shows that the power factor of compressive loads is greater and the use of the lead-acid battery to supply energy to the inverter to power compressive load will drain maximum current from it within the period of use. There was also significant disparities in the percentage of energy reservoir between the model equation results and the obtained results on the tables 4.2 and 4.3 with their graphical analyses further explained that the lead-acid battery components are deteriorating internally when is used as energy reservoir for inverter to power non-compressive and compressive loads.. The primary source of energy i. e. lead-acid battery is not rich enough to provide the needed energy to power the selected loads such as compressive and non-compressive more than of 3-4hours. The loads are selected based on the energy reservoir of the battery. The results also show that constant discharge of the lead-acid battery beyond 50% DOD will deteriorate it and shorten the life span.
vi
TABLE OF CONTENTS
TITLE
PAGE
Title page
ii
Certification
iii
Dedication
iv
Acknowledgement
v
Abstract
vi
Table of contents
vii
List of Figures
x
List of Tables
xi
List of Plates
xii CHAPTER ONE
1.0
INTRODUCTION
1.1
Background
1
1.2
Justification of the study
2
1.3
Objectives of the study
3 CHAPTER TWO
2.0
LITERATURE REVIEW
4
2.1
Solar energy utilization
4
2.2
Generation of electricity
4
2.3
Power Supply
5
2.4
Power conversion
7
2.4.1
AC-DC converters (Rectifiers)
7
2.4.2
AC in, AC out: frequency changer; cycloconverters
7
2.4.3
Dc In, Ac Out: inverter (Electrical)
8
vii
2.4.4
2.5
Basic inverter circuit designs:
9
Inverter output waveforms:
10
More advanced inverter designs:
12
DC - to -DC converters
12
Buck converter:
13
Boost converter:
14
Buck-boost converter:
14
Electrical Properties of materials in inverters
15
2.5.1
15
Power semiconductor devices Thyristor and Triac:
15
Gate Turn-Off thyristor (GTO):
16
Reverse-conducting thyristor (RCT) and asymmetrical silicon-controlled rectifier (ASCR):
18
Power transistor:
18
Power Mosfet:
19
Insulated-gate bipolar transistor (IGBT):
21
MOS-controlled thyristor (MCT):
22
2.5.2
Transformer
25
2.5.3
Capacitor
27
2.5.4
Resistor
27
2.5.5
Integrated circuit (IC)
27
2.5.6 Buzzer
28
2.5.7
Diode
28
2.5.8
Light emitting diode (LED)
28
2.5.9
Relay:
28
2.5.10 Battery:
28
2.5.11 Heat sink
29
2.5.12 Vero board
29
2.5.13 Wire:
29 viii
2.6
2.5.14 Metal casing
30
2.5.15 Oscillator
30
Domestic electric power consumption
30
CHAPTER THREE 3.0
METHODOLOGY
31
3.1
Description and working principles of 2KW Inverter
31
3.2
Design consideration for 2KW Inverter
32
3.3
Design calculation for 2KW Inverter
33
3.4
Material selection for the components
35
3.5
Assembly of components
37
3.6
Evaluation of the device
39
a. Continuity test
39
b. Test without load
39
c. Test with non-compressive load
40
d. Test with compressive load
40 CHAPTER FOUR
4.0
RESULTS AND DISCUSSION
43
4.1
Continuity test
43
4.2
Test without load
43
4.3
Test with non-compressive load
45
4.4
Test with compressive load
47 CHAPTER FIVE
5.0
CONCLUSION AND RECOMMENDATION
49
5.1
Conclusion
49
5.2
Recommendation
50
References
51
Appendix A
52
Appendix B
53
Appendix C
59
Appendix D
60 ix
LIST OF FIGURES Figure
Title
Page
2.1
Solar utilization.
6
2.2
Power Converter Family Tree
6
2.3
Simple inverter circuit shown with an electromechanical switch and with a transistor switch
2.4
11
Square waveform with fundamental sine wave component, 3rd harmonic and 5th harmonic
2.5
11
DC-DC converter configurations: (a) buck converter; (b) boost converter; (c) buck-boost converter
13
2.6
(a) Thyristor symbol and (b) volt-ampere characteristics
17
2.7
(a) Triac symbol and (b) volt-ampere characteristics
17
2.8
(a) GTO symbol and (b) turn-off characteristics
17
2.9
A two-stage Darlington transistor with bypass diode
19
2.10
Power MOSFET circuit symbol
21
2.11
Non-punch-through IGBT, (b) Punch through IGBT, (c) IGBT equivalent circuit
24
2.12
Circuit schematic for P-MCT
24
2.13
Current and future power semiconductor devices development direction24
2.14
Transformer diagram
25
3.1
Schematic Diagram of 2,000 Watts Inverter Circuit
34
4.1
DOD against test-time without load
44
4.2
DOD against test-time on non-compressive load
46
4.3
DOD against test-time on non-compressive load
48
x
LIST OF TABLES Table
Title
Page
3.1
The details of items designed
33
3.2
The electrical materials selected for the development of 2,000Watts Inverter
35
3.3
The electrical power of the non-compressive loads applied and running test period 41
3.4
The electrical power of the compressive loads applied and running test period
41
3.5
Bill of Materials
42
4.1
The result of idling load against DOD
60
4.2
The result of non-compressive load against DOD
60
4.3
Values of electrical properties of 2,000Watts Inverter
61
4.4
The result of compressive load against DOD
60
xi
LIST OF PLATES
Plate
Title
Page
3.1
Assembled components of Inverter circuit
38
3.2
The connection of Inverter to 12V, 200AH battery
38
xii
CHAPTER ONE 1.0
INTRODUCTION
1.1
Background The use of energy by man for his sustenance and well being has increased ever since he came on
earth a few million years ago. Man requires energy primarily in the form of food he ate and to provide for his shelter. With passage of time, the domestication and cultivation of animals and plants were aimed at ensuring that his need was met and he also began to use wind for sailing, driving windmill and the power of falling water to turn wheels. Agriculture has been the centre of man’s interaction and economy activities and also his energy source; is clean and renewable. Agricultural production presents many engineering problems and opportunities. Agricultural operations which include, farm structure and its comfort, soil conservation and preparation, crop cultivation and harvesting, animal production and commodities, transportation, processing, packaging and storage, and critical factors of time and place. With the challenges of food and fibre production and processing and sustaining them, started industrial revolution. It is worth saying that agriculture is mother of all profession. The industrial revolution brought many changes, the much needed flexibility in man’s movement, with the use of fossil fuels, this made energy portable. This flexibility was further enhanced with discovery of electricity for processing of food, communication and the development of control power generating station using either fossil fuels, or water or wind. This has led to a better quality life and integrated unit of human’s life. Electric power has had an impact on modern agriculture i.e. improving conditions of faming business and saves time and labour. The use of energy cannot be emphasised and there is urgent need to bring about the balance in energy budget to meet effectively the need of the people both in rural and urban areas. We live in an era
1
where we have a greater understanding that the effects of the way we generate our electricity represents a clear and present treat to our environment and to us.
Of all the electric power generation sources, the solar appears to be: i.
Environmental friendly
ii.
Inexhaustible and free
iii.
Cost effective.
The use of solar energy has also make substantial progress in the realm of technologies since the primitive man to the present time in the remote villages i.e. drying of farm products, cloth, and food preservation etc. The power from the sun intercepted by the earth is approximately 1.8 x 1011 MW (Sukhatme, 1984) which is larger than present consumption rate of all commercial energy sources. Thus in principle, solar energy could supply all the present and future energy needs of the world on continual basis. However, the main problems associated with its uses, is that, it is diluted source of energy and variation in availability occurs daily because of the day – night cycle i.e. earths orbits around the sun. With all these it can still bring about the much needed balance in the energy usage and can be used in stabilizing power supply.
1.2
Justification of the Study As the condition of farming business improved, with the flexibility of electricity in other
advanced countries, the same cannot be said of the developing countries most especially Nigeria. The versatility of electricity has led to high technology which it’s many interlocking influences shape ambitions, mould ways of seeing things and sway choices of where in the world one is to work. The main cause for mass rural urban drift. People are also attracted and held fast by better houses, hospitals,
2
schools, communication, recreation, facilities for work, salaries and career prospects have drawn many people away from rural area to urban and international centres and made farming business less attractive. In rural area, despite the fact that machines are made available but the power to keep it working is not available. Though electric power generator serves as complement of energy source but the running cost is too great for rural people to afford. While scarcity and hike in fuel price in this country, Nigeria, is at increase. The hike in fuel price between the period of early 1980’s and 2007 is 35,000 percent i.e. from 20K to N 70.00K per litre (Olaitan and Omoniy,i 2007). This shows a great reliance on fossil fuels, which does not really help rural people/dwellers and nation’s economy at large and the energy sector should not be all about income accrued from oil only but using energy sources to sustain human comforts. Also not all rural communities are connected to the power grid operated by the Power Holding Company of Nigeria (PHCN) and few that were connected do not enjoy constant electricity supply due to epileptic situation of the company. There is an urgent need to meet rural in–house electric supply and improve social well being of rural people, and salvage the urban-drift and make farming business attractive and interesting. The need for electric supply is high; the use of renewable energy such as sun and wind can generate electricity for rural area people and make them self independent. What is needed for wind as well as solar is a way to store a large energy surplus. Technology already exist to turn it into fuel such as ethanol or banking energy (battery) that can later churn out electricity.
1.3
OBJECTIVES OF THE STUDY 1.
to design and construct power inverter for farm household electricity use based on renewable energy source.
2.
to carry out the performance evaluation of such device.
3
CHAPTER TWO 2.0 2.1
LITERATURE REVIEW Solar energy utilization The intensity of solar radiation from the sun can be utilized in a variety of ways either by man or
nature. This can be grouped under two conversion methods i.e. direct methods and indirect methods by which solar energy can be utilized for its heat and power. The figure 2.1 illustrates the two conversion methods of solar energy:
2.2
Generation of electricity Generation of electricity for the purpose of powering human technologies has been going on for at
least 120 years from various sources of energy. Electricity generation is the first in the processes of delivery of electricity to consumers which also include processes such as electric power transmission and electricity distribution. The first electrical power plants were run on woods, while today we rely mainly on coal, nuclear, natural gas, hydro-electric dam and petroleum power and small amount from solar energy (photovoltaic and solar parabolic trough), wind generator and geothermal sources to generates electricity. Other electricity generation methods include Piezo-electric devices (i.e. power generation from mechanical strain); Betavoltaics (i.e. power generation from radioactive decay) and electrochemical cells (Batteries), which are also power generator. Electrochemical cells play important role in portable and mobile electrical application. Though, it is arguably utilized more as storage systems than generation systems. (http//en.wikipedia.org) The quantity of electricity required to fuel the economy is growing every day. Though, there are many public and private utilities/projects constructed to generate and transmit the electricity to meet
4
demand, but many of these projects have caused unpleasant environmental effects such as air/radiation pollution and the flooding of large areas of land.
2.3
Power supply Power supply is a device for the conversion of available power of one set of characteristics to
another set of characteristics to meet specified requirements. It makes the load compatible with its power source. Power supplies belong to the field of power electronics, the use of electronics for the control and conversion of electrical power. This technology encompasses the effective use of electronics components, the application of circuit theory and design techniques and the development of analytical tools toward efficient electronic conversion control and conditioning of electrical power. Overall, the various power supply topologies to be arranged in an applications “tree” as illustrated in figure 2.2 Basically two types of power supplies are required: Direct Current (DC) power supplies and Alternating Current (AC) power supplies. The output of dc power supplies is regulated or controllable DC/AC, whereas the output for ac power supplies could also be DC/AC. The input to these power supplies can be AC or DC.
5
Solar Energy Utilization
Direct Methods
Thermal
Indirect Methods
Photovoltaic Bio-Conversion Water Power
Wind
Bio-Mass
Ocean Temperature Differences
Figure 2.1: Solar utilization (Sukhatme, 1984)
Figure 2.2: Power Converter Family Tree (Rashid, 1988)
6
2.4
Power conversion Power conversion deals with the process of converting electric power from one form to another.
The power electronic apparatuses performing the power conversion are called power converters. Because they contain no moving parts, they are often referred to as static power converters. The power conversion is achieved using power semiconductor devices, which are used as switches. The power devices used are SCRs (silicon controlled rectifiers, or thyristors), triacs, power transistors, power MOSFETs, insulated gate bipolar transistors (IGBTs), and MCTs (MOS-controlled thyristors). The power converters are generally classified as given by Bose (1992):
2.4.1
i.
ac-dc converters (phase-controlled converters)
ii.
direct ac-ac converters (Cycloconverters)
iii.
dc-ac converters (inverters)
iv.
dc-dc converters (choppers, buck and boost converters)
AC-DC converters (Rectifiers) A rectifier is an electrical device that converts alternating current to direct current, a process
known as rectification (the opposite of inverting which converts DC to AC). Rectifiers are used as components of power supplies and as detectors of radio signals. Rectifiers may be made of solid state diodes, vacuum tube diodes, mercury arc valves, and other technologies (Bose, 1992). The primary application of rectifiers is to derive usable DC power from an AC supply. Virtually all electronics requires a DC supply but mains power is AC so rectifiers find uses inside the power supplies of virtually all electronic equipment.
2.4.2
AC in, AC out: frequency changer; cycloconverters A frequency changer or frequency converter is an electronic device that converts
alternating current (AC) of one frequency to alternating current of another frequency. The device may also change the voltage, i. e. Converters are used to change either the voltage level (i. e. 120V to 240V AC) or the utility frequency 50Hz and 60Hz power grid. A cycloconverter permits energy to be fed back
7
into the utility network without any additional measures. Also, the phase sequence of the output voltage can be easily reversed by the control system. Cycloconverters have found applications in aircraft systems and industrial drives. These cycloconverters are suitable for synchronous and induction motor control. (Bose, 1992)
2.4.3
Dc In, Ac Out: inverter (Electrical) An inverter is a circuit (made of a sophisticated microprocessor) which convert dc power to ac
power at a desired output voltage or current and frequency. The process of changing D.C to A.C is known as inversion. A static inverter circuit performs this transformation. The significant is that we are able to choose the frequency of the alternating signal and for that matter we can vary the frequency at will. An inverter allows the 12 or 24 volt (battery) DC power available in an automobile or from solar panels to supply AC power to operate equipment that is normally supplied from a mains power source. Inverters are used in a wide range of applications, from small switched power supplies for a computer to large electric utility applications to transport bulk power (Bhat, 1992). Inverters are also used to provide a source of AC power from photovoltaic solar cells and fuel cell power supplies. The terms voltage-fed and current-fed are used in connection with inverter circuits to classify it into type’s i. e. voltage source inverters (VSIs) and current source inverters (CSIs). A voltage-fed inverter (or Voltage Source Inverter) is one in which the dc input voltage is essentially constant and independent of the load current drawn. The inverter specifies the load voltage while the drawn current shape is dictated by the load. A current-fed inverter (or Current Source Inverter) is one in which the source, hence the load current is predetermined and the load impedance determines the output voltage. The supply current cannot change quickly. This is achieved by series dc supply inductance which prevents sudden changes in current. The load current magnitude is controlled by varying the input dc voltage to the large inductance; hence inverter response to load changes is slow. Being a current source, the inverter can survive an output short circuit thereby offering fault ride-through properties. Voltage control may be required to maintain a fixed output voltage when the dc input voltage regulation is poor, or to control power to a load. The inverter and its output can be single-phase, threephase or multi-phase. Variable output frequency may be required for ac motor speed control where, in conjunction with voltage or current control, constant motor flux can be maintained.
8
Inverter output waveforms are usually rectilinear in nature and as such contain harmonics which may lead to reduced load efficiency and performance. Load harmonic reduction can be achieved by filtering (Capacitors and inductors can be used to filter the waveform. Low-pass filters can also be applied to allow the fundamental component of the waveform to pass to the output while limiting the passage of the harmonic components.), selected harmonic-reduction chopping or pulse-width modulation. (Bhat, 1992) The quality of an inverter output is normally evaluated in terms of its harmonic factor, ρ, distortion factor, μ, and total harmonic distortion, (thd). These first two factors were defined in terms of the supply current. For VSI inverters the factors are redefined in terms of the output voltage harmonics as given by Owen (1996) in equation 2.1 and 2.2
………………..2.1
The distortion factor for an individual harmonic is
…………2.2
The factor Vn /n is used since the harmonic currents produced in an inductive load attenuate with frequency. The harmonic currents produce unwanted heating and torque oscillations in ac motors, although such harmonic currents are not a drawback to the power delivered to a resistive heating load or incandescent lighting load.
Basic inverter circuit designs In one simple inverter circuit, DC power is connected to a transformer through the centre tap of the primary winding. A switch is rapidly switched back and forth to allow current to flow back to the DC source following two alternate paths through one end of the primary winding and then the other. The
9
alternation of the direction of current in the primary winding of the transformer produces alternating current (AC) in the secondary circuit. (http//en.wikipedia.org) The electromechanical version of the switching device as shown in figure 2.3 includes two stationary contacts and a spring supported moving contact. The spring holds the movable contact against one of the stationary contacts and an electromagnet pulls the movable contact to the opposite stationary contact. The current in the electromagnet is interrupted by the action of the switch so that the switch continually switches rapidly back and forth. This type of electromechanical inverter switch, called a vibrator or buzzer, was once used in vacuum tube automobile radios. A similar mechanism has been used in door bells, buzzers and tattoo guns. As they have become available, transistors and various other types of semiconductor switches have been incorporated into inverter circuit designs.
Inverter output waveforms The switch in the simple inverter described above produces a square voltage waveform as opposed to the sinusoidal waveform that is the usual waveform of an AC power supply. Using Fourier analysis, periodic waveforms are represented as the sum of an infinite series of sine waves. The sine wave that has the same frequency as the original waveform is called the fundamental component. The other sine waves, called harmonics, which are included in the series, have frequencies that are integral multiples of the fundamental frequency. (http//en.wikipedia.org) The quality of the inverter output waveform as shown in figure 2.4 can be expressed by using the Fourier analysis data to calculate the total harmonic distortion (thd). The total harmonic distortion is the square root of the sum of the squares of the harmonic voltages divided by the fundamental voltage as given by (http//en.wikipedia.org)
……………2.3
The quality of output waveform that is needed from an inverter depends on the characteristics of the connected load. Some loads need a nearly perfect sine wave voltage supply in order to work properly. Other loads may work quite well with a square wave voltage.
10
Figure: 2. 3. Simple inverter circuit shown with an electromechanical switch and with a transistor switch (Owen, 1996).
Figure 2.4: Square waveform with fundamental sine wave component, 3rd harmonic and 5th harmonic (http//en.wikipedia.org).
11
More advanced inverter designs There are many different power circuit topologies and control strategies used in inverter designs. Different design approaches are used to address various issues that may be more or less important depending on the way that the inverter is intended to be used. In more advanced inverter designs various techniques are used to improve the quality of the sine wave at the transformer input, rather than relying on the transformer to smooth it. Capacitors and inductors can be used to filter the waveform at the transformer. Also, it is possible to produce a more sinusoidal wave by having split-rail direct current inputs at two voltages, or positive and negative inputs with a central ground. By connecting the transformer input terminals in sequence between the positive rail and ground, the positive rail and the negative rail, the ground rail and the negative rail, then both to the ground rail a stepped sinusoid is generated at the transformer input and the current drain on the direct current supply is less choppy. These methods result in an output that is called a “modified-sine wave”. Modified-sine wave inverters may cause some loads, such as motors, to operate less efficiently (http//en.wikipedia.org). Multilevel power inverters use Pulse-Width Modulation (PWM) with high frequency carrier to more closely approximate a sine function. The quality of an inverter is described by its pulse-rating: a three-pulse is a very simple arrangement, utilizing only 3-transistors, whereas a more complex 12-pulse system will give an almost exact sine-wave. In remote areas where a utility generated power is subject to significant external, distorting influences such as inductive loads or semiconductor-rectifier loads, a 12pulse inverter may even offer a better, “cleaner” output than the utility-supplied power grid, and are thus often used in these areas. Inverters with greater pulse ratings do exist. Simple inverters generate harmonics which affect the quality of power obtained using them. But PWM inverters eliminate this means of a sine-wave cancellation using the Fourier series.
DC - to -DC converters DC-dc converters are used to convert unregulated dc voltage to regulated or variable dc voltage at the output. They are widely used in switch-mode dc power supplies and in dc motor drive and control applications (Bose, 1992). They are called chopper-controlled drives. The input voltage source is usually
12
a battery or derived from an ac power supply using a diode bridge rectifier. These converters are generally either hard-switched PWM types or soft-switched resonant-link types. There are several dc-dc converter topologies, the most common ones being buck converter, boost converter, and buck-boost converter as shown in Figure 2.5
Figure 2.5: DC-DC converter configurations: (a) buck converter; (b) boost converter; (c) buck-boost converter. (Bose, 1992)
Buck converter A buck converter is also called a step-down converter. Its principle of operation is illustrated by referring to Figure 2.5(a). The IGBT acts as a high-frequency switch. The IGBT is repetitively closed for a time ton and opened for a time toff. During ton, the supply terminals are connected to the load, and power flows from supply to the load. During toff, load current flows through the freewheeling diode D1, and the load voltage is ideally zero. The average output voltage is given by: (Huang, 1995) V out = DV in
…………………………….2.4
Where D is the duty cycle of the switch and is given by D = ton/T, where T is the time for one period. 1/T is the switching frequency of the power device IGBT.
13
Boost converter A boost converter is also called a step-up converter. Its principle of operation is illustrated by referring to Figure 2.5(b). This converter is used to produce higher voltage at the load than the supply voltage. When the power switch is on, the inductor is connected to the dc source and the energy from the supply is stored in it. When the device is off, the inductor current is forced to flow through the diode and the load. The induced voltage across the inductor is negative. The inductor adds to the source voltage to force the inductor current into the load. The output voltage is given by Liu and Lee (1985)
……………..2.5
Thus for variation of D in the range 0 < D < 1, the load voltage Vout will vary in the range Vin < Vout <∞.
Buck-boost converter A buck-boost converter can be obtained by the cascade connection of the buck and the boost converter. The steady-state output voltage Vout is given by Philips Semiconductors (2007)
………………….2.6
This allows the output voltage to be higher or lower than the input voltage, based on the duty cycle D. A typical buck-boost converter topology is shown in Figure 2.5(c). When the power device is turned on, the input provides energy to the inductor and the diode is reverse biased. When the device is turned off, the energy stored in the inductor is transferred to the output. No energy is supplied by the input during this interval. In dc power supplies, the output capacitor is assumed to be very large, which results in a constant output voltage. In dc drive systems, the chopper is operated in step-down mode during motoring and in step-up mode during regeneration operation. Philips Semiconductors (2007)
14
2.5
Electrical properties of materials in inverters
The following are electrical materials incorporated in inverter circuit design: i. Power
semiconductor
vi.
Buzzer
xii.
Vero board
devices
vii.
Diode
xiii.
Metal casing
ii. Transformer
viii.
LED
xiv.
Wires
iii. Capacitor
ix.
Relay
xv.
Oscillator
iv. Resistor
x.
Battery
v.
xi.
Heat sink
2.5.1
Integrated circuit
Power semiconductor devices The modern age of power electronics began with the introduction of thyristors in the late 1950s. Now
there are several types of power devices available for high-power and high-frequency applications. The most notable power devices are gate turn-off thyristors, power Darlington transistors, power MOSFETs, and insulated-gate bipolar transistors (IGBTs). Power semiconductor devices are the most important functional elements in all power conversion applications. The power devices are mainly used as switches to convert power from one form to another. They are used in motor control systems, uninterrupted power supplies, highvoltage dc transmission, power supplies, induction heating, and in many other power conversion applications. (Bose, 1992) Thyristor and Triac The thyristor, also called a silicon-controlled rectifier (SCR), is basically a four-layer three-junction Pnpn device. It has three terminals: anode, cathode, and gate. The device is turned on by applying a short pulse across the gate and cathode. Once the device turns on, the gate loses its control to turn off the device. The turn-off is achieved by applying a reverse voltage across the anode and cathode. The thyristor symbol and its volt-ampere characteristics are shown in Figure 2.6. There are basically two classifications of thyristors: converter grade and inverter grade (Bose, 1992). The difference between a converter-grade and an inverter-grade thyristor is the low turn-off time (on the order of a few microseconds) for the latter. The converter-grade thyristors are slow type and are used in natural commutation (or phase-controlled) applications. Inverter-grade thyristors are used in forced commutation applications such as dc-dc choppers and dc-ac inverters. The inverter-grade thyristors are turned off by forcing the current to zero using an
15
external commutation circuit. This requires additional commutating components, thus resulting in additional losses in the inverter. Thyristors are highly rugged devices in terms of transient currents, di/dt, and dv/dt capability. The forward voltage drop in thyristors is about 1.5 to 2 V, and even at higher currents of the order of 1000 A, it seldom exceeds 3 V. While the forward voltage determines the on-state power loss of the device at any given current, the switching power loss becomes a dominating factor affecting the device junction temperature at high operating frequencies. Because of this, the maximum switching frequencies possible using thyristors are limited in comparison with other power devices considered in this section. Thyristors have I2t withstand capability and can be protected by fuses. The non-repetitive surge current capability for thyristors is about 10 times their rated root mean square (rms) current. They must be protected by snubber networks for dv/dt and di/dt effects. If the specified dv/dt is exceeded, thyristors may start conducting without applying a gate pulse. In dc-to-ac conversion applications it is necessary to use an antiparallel diode of similar rating across each main thyristor. Thyristors are available up to 6000 V, 3500 A. A triac is functionally a pair of converter-grade thyristors connected in antiparallel. The triac symbol and volt-ampere characteristics are shown in Figure 2.7. Because of the integration, the triac has poor reapplied dv/dt, poor gate current sensitivity at turn-on, and longer turn-off time. Triacs are mainly used in phase control applications such as in ac regulators for lighting and fan control and in solid-state ac relays (Bose, 1992) Gate Turn-off Thyristor (GTO) The GTO is a power switching device that can be turned on by a short pulse of gate current and turned off by a reverse gate pulse. This reverse gate current amplitude is dependent on the anode current to be turned off. Hence there is no need for an external commutation circuit to turn it off. Because turn-off is provided by bypassing carriers directly to the gate circuit, its turn-off time is short, thus giving it more capability for high frequency operation than thyristors. The GTO symbol and turn-off characteristics are shown in Figure 2.8. GTOs have the I2t withstand capability and hence can be protected by semiconductor fuses. For reliable operation of GTOs, the critical aspects are proper design of the gate turn-off circuit and the snubber circuit (Bose, 1992). A GTO has a poor turn-off current gain of the order of 4 to 5. For example, a 2000A peak current GTO may require as high as 500 A of reverse gate current. Also, a GTO has the tendency to latch at temperatures above 1250C. GTOs are available up to about 4500 V, 2500 A.
16
Figure 2.6: (a) Thyristor symbol and (b) volt-ampere characteristics. (Bose, 1992)
Figure2.7: (a) Triac symbol and (b) volt-ampere characteristics. (Bose, 1992)
Figure 2.8: (a) GTO symbol and (b) turn-off characteristics. (Bose, 1992)
17
Reverse-conducting thyristor (RCT) and Asymmetrical silicon-controlled rectifier (ASCR) Normally in inverter applications, a diode in anti-parallel is connected to the thyristor for commutation/freewheeling purposes. In RCTs, the diode is integrated with a fast switching thyristor in a single silicon chip. Thus, the number of power devices could be reduced. This integration brings forth a substantial improvement of the static and dynamic characteristics as well as its overall circuit performance. The RCTs are designed mainly for specific applications such as traction drives. The antiparallel diode limits the reverse voltage across the thyristor to 1 to 2V. Also, because of the reverse recovery behavior of the diodes, the thyristor may see very high reapplied dv/dt when the diode recovers from its reverse voltage. This necessitates use of large RC snubber networks to suppress voltage transients. As the range of application of thyristors and diodes extends into higher frequencies, their reverse recovery charge becomes increasingly important. High reverse recovery charge results in high power dissipation during switching. The ASCR has a similar forward blocking capability as an invertergrade thyristor, but it has a limited reverse blocking (about 20–30V) capability. It has an on-state voltage drop of about 25% less than an inverter-grade thyristor of a similar rating. The ASCR features a fast turn-off time; thus it can work at a higher frequency than an SCR. Since the turn-off time is down by a factor of nearly 2, the size of the commutating components can be halved. Because of this, the switching losses will also be low. Gate-assisted turn-off techniques are used to even further reduce the turn-off time of an ASCR. The application of a negative voltage to the gate during turn-off helps to evacuate stored charge in the device and aids the recovery mechanisms. This will in effect reduce the turn-off time by a factor of up to 2 over the conventional device. (Bose, 1992)
Power transistor Power transistors are used in applications ranging from a few to several hundred kilowatts and switching frequencies up to about 10 kHz. Power transistors used in power conversion applications are generally NPN type. The power transistor is turned on by supplying sufficient base current, and this base drive has to be maintained throughout its conduction period. It is turned off by removing the base drive and making the base voltage slightly negative (within – VBE (max)). The saturation voltage of the device is
18
normally 0.5 to 2.5 V and increases as the current increases. Hence the on-state losses increase more than proportionately with current. The transistor off-state losses are much lower than the on-state losses because the leakage current of the device is of the order of a few milli-amperes. Because of relatively larger switching times, the switching loss significantly increases with switching frequency. Power transistors can block only forward voltages. The reverse peak voltage rating of these devices is as low as 5 to 10 V. Power transistors do not have I2t withstand capability. In other words, they can absorb only very little energy before breakdown. Therefore, they cannot be protected by semiconductor fuses, and thus an electronic protection method has to be used. To eliminate high base current requirements, Darlington configurations are commonly used. They are available in monolithic or in isolated packages. The basic Darlington configuration is shown schematically in Figure 2.9. The Darlington configuration presents a specific advantage in that it can considerably increase the current switched by the transistor for a given base drive. The VCE(sat) for the Darlington is generally more than that of a single transistor of similar rating with corresponding increase in on-state power loss. During switching, the reverse-biased collector junction may show hot spot breakdown effects that are specified by reverse-bias safe operating area (RBSOA) and forward bias safe operating area (FBSOA). Modern devices with highly inter-digited emitter base geometry force more uniform current distribution and therefore considerably improve second breakdown effects. Normally, a well-designed switching aid network constrains the device operation well within the SOAs: (Bose, 1992)
Figure 2.9: A two-stage Darlington transistor with bypass diode. (Bose, 1992)
Power mosfet Power MOSFETs are marketed by different manufacturers with differences in internal geometry and with different names such as MegaMOS, HEXFET, SIPMOS, and TMOS. They have unique
19
features that make them potentially attractive for switching applications. They are essentially voltagedriven rather than current-driven devices, unlike bipolar transistors. The gate of a MOSFET is isolated electrically from the source by a layer of silicon oxide. The gate draws only a minute leakage current of the order of nano-amperes. Hence the gate drive circuit is simple and power loss in the gate control circuit is practically negligible. Although in steady state the gate draws virtually no current, this is not so under transient conditions. The gate-to-source and gate-to-drain capacitances have to be charged and discharged appropriately to obtain the desired switching speed, and the drive circuit must have a sufficiently low output impedance to supply the required charging and discharging currents. The circuit symbol of a power MOSFET is shown in Figure 2.10. Power MOSFETs are majority carrier devices, and there is no minority carrier storage time. Hence they have exceptionally fast rise and fall times. They are essentially resistive devices when turned on, while bipolar transistors present a more or less constant VCE(sat) over the normal operating range. Power dissipation in MOSFETs is Id2RDS(on), and in bipolar it is ICVCE(sat). At low currents, therefore, a power MOSFET may have a lower conduction loss than a comparable bipolar device, but at higher currents, the conduction loss will exceed that of bipolar. Also, the RDS(on) increases with temperature. An important feature of a power MOSFET is the absence of a secondary breakdown effect, which is present in a bipolar transistor, and as a result, it has an extremely rugged switching performance. In MOSFETs, RDS(on) increases with temperature, and thus the current is automatically diverted away from the hotspot. The drain body junction appears as an anti-parallel diode between source and drain. Thus power MOSFETs will not support voltage in the reverse direction. (Bose, 1992) Although this inverse diode is relatively fast, it is slow by comparison with the MOSFET. Recent devices have the diode recovery time as low as 100 ns. Since MOSFETs cannot be protected by fuses, an electronic protection technique has to be used. With the advancement in MOS technology, ruggedized MOSFETs are replacing the conventional MOSFETs. The need to ruggedize power MOSFETs is related to device reliability. If a MOSFET is operating within its specification range at all times, its chances for failing catastrophically are minimal. However, if its absolute maximum rating is exceeded, failure probability increases dramatically. Under actual operating conditions, a MOSFET may be subjected to transients - either externally from the power bus supplying the circuit or from the circuit itself due, for example, to inductive kicks going beyond the absolute maximum ratings.
20
Such conditions are likely in almost every application, and in most cases are beyond a designer’s control. Rugged devices are made to be more tolerant for over-voltage transients. Ruggedness is the ability of a MOSFET to operate in an environment of dynamic electrical stresses as explained by Bose (1992), without activating any of the parasitic bipolar junction transistors. The rugged device can withstand higher levels of diode recovery dv/dt and static dv/dt.
Figure 2.10: Power mosfet circuit symbol. (Bose, 1992)
Insulated-gate bipolar transistor (IGBT) According to Motorola (2008), the IGBT has the high input impedance and high-speed characteristics of a MOSFET with the conductivity characteristic (low saturation voltage) of a bipolar transistor. The IGBT is turned on by applying a positive voltage between the gate and emitter and, as in the MOSFET, it is turned off by making the gate signal zero or slightly negative. The IGBT has a much lower voltage drop than a MOSFET of similar ratings. The structure of an IGBT is more like a thyristor and MOSFET. For a given IGBT, there is a critical value of collector current that will cause a large enough voltage drop to activate the thyristor. Hence, the device manufacturer specifies the peak allowable collector current that can flow without latch-up occurring. There is also a corresponding gate source voltage that permits this current to flow that should not be exceeded. Like the power MOSFET,
21
the IGBT does not exhibit the secondary breakdown phenomenon common to bipolar transistors. However, care should be taken not to exceed the maximum power dissipation and specified maximum junction temperature of the device under all conditions for guaranteed reliable operation. The on-state voltage of the IGBT is heavily dependent on the gate voltage. To obtain a low on-state voltage, a sufficiently high gate voltage must be applied. In general, IGBTs can be classified as punch-through (PT) and non-punch-through (NPT) structures, as shown in Figure 2.11. In the PT IGBT, an N+ buffer layer is normally introduced between the P+ substrate and the N – epitaxial layer, so that the whole N – drift region is depleted when the device is blocking the off-state voltage, and the electrical field shape inside the N – drift region is close to a rectangular shape. Because a shorter N – region can be used in the punch-through IGBT, a better tradeoff between the forward voltage drop and turn-off time can be achieved. PT IGBTs are available up to about 1200 V. High voltage IGBTs are realized through non-punch- through process. The devices are built on a N – wafer substrate which serves as the N – base drift region. Experimental NPT IGBTs of up to about 4 KV have been reported in the literature. NPT IGBTs are more robust than PT IGBTs particularly under short circuit conditions. But NPT IGBTs have a higher forward voltage drop than the PT IGBTs. The PT IGBTs cannot be as easily paralleled as MOSFETs. The factors that inhibit current sharing of parallel-connected IGBTs are (1) on-state current unbalance, caused by VCE(sat) distribution and main circuit wiring resistance distribution, and (2) current unbalance at turn-on and turn-off, caused by the switching time difference of the parallel connected devices and circuit wiring inductance distribution. The NPT IGBTs can be paralleled because of their positive temperature coefficient property
MOS-controlled thyristor (MCT) The MCT is a new type of power semiconductor device that combines the capabilities of thyristor voltage and current with MOS gated turn-on and turn-off. It is a high power, high frequency, low conduction drop and a rugged device, which is more likely to be used in the future for medium and high power applications. A cross sectional structure of a p-type MCT with its circuit schematic is shown in Figure 2.12. The MCT has a thyristor type structure with three junctions and PNPN layers between the
22
anode and cathode. In a practical MCT, about 100,000 cells similar to the one shown are paralleled to achieve the desired current rating. MCT is turned on by a negative voltage pulse at the gate with respect to the anode, and is turned off by a positive voltage pulse. The MCT was announced by the General Electric R & D Center on November 30, 1988. Harris Semiconductor Corporation has developed two generations of p-MCTs. Gen-1 p-MCTs are available at 65 A/1000 V and 75A/600V with peak controllable current of 120 A. Gen-2 p-MCTs are being developed at similar current and voltage ratings, with much improved turn-on capability and switching speed. The reason for developing p-MCT is the fact that the current density that can be turned off is 2 or 3 times higher than that of an n-MCT; but nMCTs are the ones needed for many practical applications. Motorola (2008) The advantage of an MCT over-IGBT is its low forward voltage drop. N-type MCTs will be expected to have a similar forward voltage drop, but with an improved reverse bias safe operating area and switching speed. MCTs have relatively low switching times and storage time. The MCT is capable of high current densities and blocking voltages in both directions. Since the power gain of an MCT is extremely high, it could be driven directly from logic gates. An MCT has high di/dt (of the order of 2500 A/µs) and high dv/dt (of the order of 20,000 V/µs) capability. The MCT, because of its superior characteristics, shows a tremendous possibility for applications such as motor drives, uninterrupted power supplies, static VAR compensators, and high power active power line conditioners. The current and future power semiconductor devices developmental direction is shown in Figure 13. High temperature operation capability and low forward voltage drop operation can be obtained if silicon is replaced by silicon carbide material for producing power devices. Motorola (2008) The silicon carbide has a higher band gap than silicon. Hence higher breakdown voltage devices could be developed. Silicon carbide devices have excellent switching characteristics and stable blocking voltages at higher temperatures. But the silicon carbide devices are still in the very early stages of development.
23
Figure 2.11: Non-punch-through IGBT, (b) Punch through IGBT, (c) IGBT equivalent circuit. (Motorola, 2008)
Figure 2.12: Circuit schematic for P-MCT
Figure 2.13: Current and future power
(Motorola, 2008)
semiconductor devices development direction (Motorola, 2008)
24
2.5.2
Transformer A transformer is an electro-static device that has ability and capability to step up or step down the
input voltage supplied to it. The output voltage of the transformer is base on the circuit voltage requirement, it convert Alternating Current (A.C) to Direct Current (D.C). The transformer is wound in two directions such as;
a) Primary Winding: This is the input voltage (A.C) of the transformer which determined the output voltage (D.C).
b) Secondary Winding: This is the output voltage (D.C) of a transformer that is directed to the load. The output voltage (D.C) varies due to different circuit, different voltage and different operation.
Figure 2.13: Transformer diagram (DBTI, 2005) The power and efficiency of a transformer depends on the number of turns wound on both the primary and secondary winding and the lamination used to reduced the core losses. Other types of transformer include Auto transformer, Current transformer, Potential transformer, Core type transformer, Shell type transformer. To know the amount of flux produced by primary passes through the secondary, the electromotive force (E.M.F) produced in each turn is the same as primary and secondary hence N1 and N2 being the number of turns in primary and secondary respectively as given by DBTI training manual:
25
Total E.M.F in secondary Total E.M.F in primary
N2 x E.M.F /turns N1 x E.M.F /turns
E2
=
N2
………………………….2.7
=
N1
E1
I1 I2.
………………………….2.8
OR V2
=
V1
N2 N1
=
I1 I2
………………………….2.9
Efficiency of a Transformer: This is losses which occur in a transformer on – load and it can be divided into groups as given by DBTI (2005) a. b.
Copper Losses: It is divided into two such as: primary losses = I2R, secondary losses = I2 R2 Core Losses: This is due to eddy current or hysteresis since the maximum value of the flux in the transformer does not vary by more than about 2 percent between no – load and full – load. It is usually assumed that the core loss is constant at all loads. Hence PC = total core losses Total loss in transformer = PC + I2R + I2R2 Efficiency = Output power Input power Output power = V X I X P.F Input power = output power + total losses = V X I X P.F + I2 R, + I2 R2.
Efficiency = V X I X P.F
X
100%
V X I X P.F + I2 R + I2R2
………………2.10
26
2.5.3
Capacitor (
)
This is an electronics device that is used to store electric charges in an electrical circuit. A capacitor is used with a resistor in a timing circuit. It can also be used as a filter, smoothing of alternating current (A.C) supply i. e. to block DC signals but pass AC signals. The unit of capacitor is micro- Faraday’s and the amount of change store by a capacitor is given by DBTI (2005) ……..………………………………………………….2.11
Q=C–V
Where, Q = Amount of charge in coulomb © V = Voltage in the circuit in volt (V) C = Capacitance in Faraday’s (F) Capacitor is use in store energy. E = Q V Where, E = Energy store in joules (J)
2.5.4
Resistor: (
)
This is an electronics component that is used to restrict the flow of current electrical circuit, for example to limit the current passing through a LED. A resistor is used with a capacitor in a timing circuit. The unit of resistor is ohms (Ω). (DBTI, 2005)
2.5.5
Integrated circuit (IC) This is an electronic device that has a reduced the size, weight and power requirement of today
electronic gadget and replace transistor as transistor replaced vacuum tubes. It contains microscopically small electronic components such as: Diodes, Transistors, Resistors and Capacitors. It is classified into two such as digital and linear integrated circuit (IC). Digital IC is used in computer, calculators and digital clock as well as many other digital devices. Linear IC is used in audio amplifiers, voltage regulators, operational amplifiers and radio frequency circuit and most of linear IC is low power devices. (Wojslawowicz, 2005)
27
2.5.6
Buzzer This is an electronics device or a transducer which converts electrical energy to sound. It can
be used to indicate when there is power failure and power supply. (Wojslawowicz, 2005)
2.5.7 Diode This is an electronic device which only allows current to flow in one direction. It can be used for the conversion of alternating current (A.C) to direct current (D.C). It is made of semi-conductor material (Silicon). (Wojslawowicz, 2005)
2.5.8
Light emitting diode (LED) This is an electrical/electronic transducer which converts electrical energy to light. It is used to
indicate whether a circuit is energised or not (i.e. If current is present in the circuit) and is connected to group of resistor in series to divide the voltage passing across to the LED. (Mohan and Undeland, 1995)
2.5.9
Relay: This is an electronic component that is working with the principle of electromagnetic induction
and as the ability and capability of making and breaking of a contact. It has normally opened (NO) and normally closes (NC) contacts. (DBTI, 2005)
2.5.10
Battery: A battery is a device in which chemical energy is directly converted to electrical energy. It
consists of one or more voltaic cells, each of which comprises two half-cells connected in series by the conductive electrolyte. A battery consists of one or more voltaic cells in series. Each cell has a positive electrode (cathode), and a negative electrode (anode). These do not touch each other but are immersed in a solid or liquid electrolyte. In a practical cell the materials are enclosed in a container, and a separator between the electrodes prevents them from touching one another. Batteries are usually divided into two broad classes:
28
Primary batteries irreversibly transform chemical energy to electrical energy. Once the initial
i.
supply of reactants is exhausted, energy cannot be readily restored to the battery by electrical means. Secondary batteries can be recharged, that is, have their chemical reactions reversed by
ii.
supplying electrical energy to the cell, restoring their original composition. The types of secondary batteries that can be used for inverters are; a.
Car (Very short life) – not recommended
b.
Marine (Short Life) – the bare minimum
c.
Golf cart (5 to 8 years)
d.
Deep cycle L16s (7 to 10 years)
e.
Industrial (10 to 30 years)
The years stated are achievable only if the battery is not discharged below 50% DOD of cycle and with proper maintenance. (www.outbackpower.com)
2.5.11
Heat sink This is a device that is made up of aluminium which is use to absorbed heat generated by semiconductor devices i. e. transistors. It has high heat absorption ability due to the material it’s made of. (Harris Semiconductor, 2000)
2.5.12
Vero board This is an electronics panel or platform that is used to connect electronic components together to make up electrical/electronic system. (DBTI, 2005)
2.5.13
Wire: (
)
This is an electrical material, which pass current very easily from one part of a circuit to another. (DBTI, 2005)
29
2.5.14
Metal casing This is a material that stands as a body of the work (i.e. Material that cover all the component
after it has been coupled or connected together). It resists external reaction on the components. (DBTI, 2005)
2.5.15
Oscillator
This is a component which converts direct current into high frequency alternating current. Different IC used as oscillators are 555Timer, CD4047, MM5369, and SG3224 (Harris Semiconductor, 2000). Oscillators are circuits that produce specific, periodic waveforms such as square, triangular, saw tooth, and sinusoidal. They generally use some form of active device, lamp, or crystal, surrounded by passive devices such as resistors, capacitors, and inductors, to generate the output.
2.6
Domestic electric power consumption Consumption of electrical power varies from one place to another. PHCN, (2009) stated that the
average and ideal electrical power consumed per house within the Akure community is given as follows: i.
Average electrical power consumed per house in a day is 6.5 kilowatts
ii.
Ideal electrical power consumption per house in a day is about 10 kilowatts
iii.
Average electrical power consumed per house in a month is 200 kilowatts
iv.
Ideal electrical power consumption per house in a month is about 300 kilowatts
30
CHAPTER THREE 3.0 METHODOLOGY 3.1 Description and working principles of 2KW Inverter The 2KW inverter designed for farm household is an integrated version of current and voltagefed static circuitry* made of sophisticated microprocessors (such as FETS, oscillators etc) which performs the transformation of input DC power to AC power with transformer as integral of the system at a desired operating output voltage of 220 – 240V and 50Hz frequency. The significant of this is that we are able to choose the frequency of the alternating signal and for that matter we can vary the frequency at will. This inverter allows only the use of 12 volt (battery) DC power available in an automobile/marine battery/fuel cells/solar panels to supply AC power to operate equipment that is normally supplied from a mains power source. The methodology used to achieve the objectives focused on the design of transformer as the main integral part of the inverter, while the design and selection of other components were based on their electrical properties and affordability. The inverter was designed as a 12-pulse inverter i.e. consists of 12 IRFP 260N FETS transistors to smoothing and supply electric power The sinusoidal waveform of the load harmonic modulation was achieved by filtering i. e. Capacitors and inductors were used to filter the waveform. Low-pass filters were also to smoothing further the waveform of the inverter thereby making the pulse-width modulation of the inverter similar to the sinusoidal waveform of PHCN power grid. The 2KW power inverter for farm household operates on the principle of Inversion of power supply, in the sense that when there is power supply (A.C) from PHCN it will charge the battery and at the same time passing current to the appliances connected to it. Immediately there is failure in the power supply it will continue the power supply, feeding from the D.C source i. e. Battery, within micro-second without affecting the operation of the appliance connected to it. It can also work independent of the grid.
*Details about Current/Voltage fed Inverter is on page 8
31
3.2 Design Consideration for 2KW Inverter The design, selection of electrical materials and development of this inverter device were based on the following criteria: a.
Design of 2181Watts transformer (Note that the little wattage increased is meant to compensate for power loss within the circuit)
b.
Availability i.e. locally available, especially of being easily accessible or obtainable
c.
Durability i.e. the ability of the materials to work for long period of time without damaging its thermal and electrical properties.
d.
Cost affordability
e.
Thermal properties of the material
f.
Electrical properties of the material
The details of the designed and selected materials for the 2,000Watts are shown in Table 3.2. Inverter rating is based on its pulse i.e. pulse width modulation. To achieve this, IGBT is the most suitable because it has the high input impedance and high-speed characteristics of a MOSFET with the conductivity characteristic (low saturation voltage) of a bipolar transistor. IGBT is costly and is not readily available in the market. This necessitates me to choose the closest material i. e. MOSFETS IRFP 260N in the terms of cost and electrical properties for the design of the inverter as shown in figure 3.1 and Appendix C.
32
3.3
Design Calculation for 2KW Inverter
The summary details calculation of transformer design, the electrical characteristics of the Power
Mosfet - IRFP 260N to be used in 2KW inverter are shown in table 3.1. The full details and electrical details of the battery are on appendix B and C
Table 3.1: The details of items designed
a. Transformer Section of the Coil OUTPUT POWER
Voltage Number of Turns
Area
(Watts)
(Volts) 2
(mm ) N1 ≈ 19
S1 = 1.14
V1 = 240
N 2 ≈ 10
S2 = 27.5
V2 = 12
2,181
b. Power Mosfet - IRFP 260N Voltage
Current
200Volts
50Ampere
c. Battery, (Lead –acid accumulator)
Voltage
Ampere Hour
Power
12Vdc
200AH
2400VAdc
33
Figure 3.1: Schematic Diagram of 2KW Inverter Circuit
34
3.4 Material selection for the Inverter components The criteria of selecting electrical materials used in the development of 2KW inverter device were outlined in the table below:
Table 3.2: The electrical materials selected for the development of 2,000Watts Inverter CRITERIA FOR
MATERIAL
REASON FOR
SELECTION
SELECTED
SELECTION
S/N COMPONENTS
Step up of input voltage It should be able to to
High
voltage
and
supply
the
step up voltage and Step up transformer i. Transformer
ability meet
to
2,000Watts from 12V – 260V needed power output, i. e.
output 2,000 Wattage
High ii. FETS Transistor
Fast switching
IRFP 260N
amplification
current
and
of cost
affordability
To iii. Capacitor
To deal with power
10 V, 4700 UF mica
store
charges
temporarily
and
smoothing the current. 10KΩ, 100Ω, 39Ω, High current and iv. Resistor
50KΩ
thermal resistance
of
variable
To reduced the flowing of current across the circuit and serves as voltage
resistor divider.
35
To be able to v. Battery
Lead-acid
charge and
Cost affordability accumulator
discharge for long duration of time Rectification
of
vi. Diode
To convert from A.C to 5339
current
D.C To indicate present of
To
serve
as
vii. LED
3 – 9 V LED
electrical current in the
indicator circuit To produce sound when To
serve
as
viii. Buzzer
SFM – 27
current enter and out of
indicator the circuit. ix. Heat sink
Heat dissipation To
pass
Thick aluminium
Good conductor of heat.
current Passage of current from
x.
very easily from 0.5m2 & 2.5mm2 wire
Wire
one part of a circuit to
one part of a circuit another. to another. To serve as housing and
packaging
High
resistance
to
SWG – 18 galvanized xi. Metal casing
material
for
all
corrosion
and
plate. components
of
inverter
36
beautification.
easy
3.5
Assembly of Components The assembly of inverter components was done in the electrical workshop of Don Bosco
Technical institute of Electrical Engineering and Maintenance, Akure. The following were the steps taken to ensure proper installation of the Inverter:
i.
Construction was all done point to point on the Vero-board.
ii.
The transformer is relatively large and heavily laminated. The E and I sheets alternate direction to minimize electromagnetic flux loss. There are insulating layers between each of the primary and secondary windings. The number of turns in the output winding was determined based on its measured resistance, core diameter, and the wire gauge table. (also see the appendix II for the transformer calculation)
iii.
The FETs transistor were marked IRFP 260N is a close match of high power amplifier switch 200V, 50A, 0.04Ω, 300W. The transistors are mounted on heat sinks which form the sides of the case.
iv.
Other components such as capacitors, resistors, integrated circuit, relays, diodes and chokes, where all connected on the Vero-board accordingly to the way they were shown on the circuit diagram.
v.
The assembled components were then placed in the metal casing as it is being shown in plate 3.1
37
Plate 3.1: Assembled components of Inverter circuit
Plate 3.2: The connection of Inverter to 12V, 200AH battery
38
3.6
Evaluation of the Device The following tests were carried out on newly constructed power inverter was done in the
electrical workshop of Don Bosco Technical institute of Electrical Engineering and Maintenance, Akure.
i.
Continuity test
ii.
Test without load
iii.
Test with compressive load
iv.
Test with non-compressive load
Load testing is carried to verify that the inverter when connected with battery can deliver its specified power when needed and to size with require battery.
a. Continuity Test:
This test was carried out to determine that every continuity wire on the device is functioning and they are in proper working condition so that when current is supply to the circuit, it will be able to carry out necessary operation and prevent short circuit.
b.
Test without Load:
This test was carried out on a newly constructed 2,000Watts Power Inverter when it has been connected to the fully charged battery of 12V, 200Amp Hour. This enable me to know if the input and the output voltages are functioning as it was expected of it and also check the temperature of the heat sink in the circuit. The battery monitoring device was attached to the battery to determine the discharge rate of the battery without load and current consume by the inverter when it is idling.
39
c.
Test with non-compressive Load
This test was carried on newly constructed Inverter. A non-compressive load of 1,916Watts were applied to the inverter output. Table 3.3 shows the electrical power of the noncompressive loads applied and running test period. The battery monitoring device was attached to the battery to determine the discharge rate of the battery with efficiency of the inverter when connected to the non-compressive applied load. Non-compressive load requires no extra electrical power /current /torque for starting up or operation.
d.
Test with compressive load
This test was carried on newly constructed Inverter. A non-compressive load of 1,455Watts were applied to the inverter output. Table 3.4 shows the electrical power of the compressive loads applied and running test period. The battery monitoring device was attached to the battery to determine the discharge rate of the battery with efficiency of the inverter when connected to the compressive applied load. Compressive loads require 5 times of their electrical power /current /torque for starting up or operation.
40
Table 3.3: The electrical power of the non-compressive loads applied and running test period
Home Appliance
Power rating
Type
Quantity
(Watts)
Florescent
Energy saving
lamp
lamp
Lamp
Appliance
Energy
Running
consumed
Test-time
per appliance
(Hours)
(Watts)
20
1
4
80
40
1
4
160
60
1
4
240
100
1
4
400
200
1
4
800
59
1
4
236
ii
14 TV colour
Total energy consumed
1,916
Table 3.4: The electrical power of the compressive loads applied and running test period
Energy Appliance Home
consumed Power rating
Appliance
Type
Running Quantity
(Watts)
per Test-time appliance (Hours) (Watts)
Table
50
1
3
150
Standing
135
1
3
405
300
1
3
900
Fan Water
No
Pump
automatic
Total energy consumed
41
1455
Table 3.5: Bill of Materials
PARTS QUANTITY
DESCRIPTION
Step-up transformer (12V-
UNIT
TOTAL
COST
COST
N:K
N:K
15,500
15,500
i.
1
ii.
12
FETS Transistors (IRFP 260N)
460
5,520
iii.
1
Heat sink
700
700
iv.
1
Metal casing
4,500
4,500
v.
10
1N400 Silicon Diode
50
500
vi.
10
Capacitors
50
500
vii.
20
Resistors
50
1,000
viii.
2
Integrated circuit (I C)
450
900
ix.
1 roll
Soldering lead
950
950
x.
1
Vero board
450
450
xi.
6
LED
50
300
xii.
1
Buzzer
150
150
xiii.
2 yards
Wire
100
200
xiv.
1
Plug
180
180
xv.
2
Crocodile clip
50
100
xvi.
1
Battery (Dry cell)
2,500
Transportation
3,500
TOTAL
37,450
xvii.
260V) 2,000Watts output.
Research base on the internet work and printing of the work cost N3, 500.00. Workmanship (Cost of soldering and coupling of materials) = N 4,500.00 Total cost of production = N (37,450+ 3,500 + 4,500) = N45, 450
42
CHAPTER FOUR 4.0
RESULTS AND DISCUSSION The results of the evaluation carried out on the inverter such as continuity test; test without load; test with compressive load; and test with non-compressive load are given as follows:
4.1
Continuity Test: The continuity test was done to ensure that there is no leakage of current and short circuit on the circuitry. I also, tested the device for continuity range. The circuitry was found to be functioning. When carry out this test, multi-meter instrument was used.
4.2
Test without Load This test was carried out to determine the power consumption rate or the idling power of the inverter when connected to the fully charged battery of 12V, 200Amp Hour and is not on any applied load. The data generated on table 4.1 as shown in appendix D is illustrated in the figure 4.1: DOD against test-time without load. The horizontal axis measures the test-time in hours. The vertical axis gives the depth of discharge in percentage (%) as it is been monitored by battery monitoring device attached to the battery. The equation of figure 4.1 is given as: y = −1.8 x + 102.2
.............4.1
This shows that for the 4hours test period of using the inverter without applied load, 5% of the actual total battery charges was consumed i.e. 120VAdc x = 4hours; y = 95%
It can be deduced from the above analysis that the inverter uses averagely 30VAdc of battery energy per hour and it will take the inverter 40hours to discharge the battery to 50% DOD (the acceptable level) of continuous use without applied load. Conversely, as the test-time increases, the battery energy reservoir will continue to decrease.
43
110
100
90
DEPTH OF DISCHARGE (%)
80
70
y = -1.8x + 102.2 R2 = 0.9878
60
50
40
30
20
10
0 0
1
2
3
TIME (hours)
Figure 4.1: DOD AGAINST TEST-TIME WITHOUT LOAD
44
4
4.3
Test with non-compressive Load
This test was carried out to determine the effect of non-compressive loads has on the fully charged battery of 12V, 200Amp Hour when is connected to the inverter. The data generated on table 4.2 as shown in appendix D is illustrated in the figure 4.2: DOD against test-time on non-compressive load. The horizontal axis measures the test-time in hours. The vertical axis gives the depth of discharge in percentage (%) as it is been monitored by battery monitoring device attached to the battery. The equation of the figure 4.2 is given as: y = −14.4 x + 112.4
.............4.2
This shows that for the 4hours test period of using the inverter without applied load, 54.8% of the actual total battery charges was consumed i.e. 1,315.2VAdc x = 4hours; y = 45.2%
It can be deduced from the above analysis that the non-compressive loads consumed more than the average of battery charges of battery energy within 4hours of test period. It consumed averagely 328.75VAdc of battery energy per hour of use with non-compressive loads. This shows that the battery can only be used for 3hours period against the non-compressive loads, to keep the depth of discharge within acceptable level of 50%. There is a little difference from the model equation and the result on the table 4.2, this may due to the internal friction/reaction of the lead-acid battery components which we did not account for during design analysis or test of the device.
The electrical property of the inverter was measured when connected to applied loads with Clamp-on meter. The results obtained on table 4.3 were tabulated against designed values as shown in appendix D.
45
110 100 y = -14.4x + 112.4 R² = 0.994
90
DEPTH OF DISCHARGE (%)
80 70 60 50 40 30 20 10 0 0
1
2
3
TIME (hours)
Figure 4.2: DOD AGAINST TEST-TIME ON NON-COMPRESSIVE LOAD
46
4
4.4
Test with compressive Load This test was carried out to determine the effect of compressive loads has on the fully charged
battery of 12V, 200Amp Hour when is connected to the inverter. The data generated on table 4.4 as shown in appendix D is illustrated in the figure 4.3: DOD against test-time on compressive load. The horizontal axis measures the test-time in hours. The vertical axis gives the depth of discharge in percentage (%) as it is been monitored by battery monitoring device attached to the battery. The equation of the figure 4.3 is given as: y = −21.8 x + 129
.............4.3
This shows that for the 3hours test period of using the inverter without applied load, 63.6% of the actual total battery charges was consumed i.e. 1,526.4VAdc that is x = 3hours; y = 36.4%
There is a great disparity of 16% of energy reservoir between the model equation results and the obtained results on the table 4.3. This further explained that the lead-acid battery components deteriorate internally faster when is used as energy reservoir for inverter to power compressive load. We may say that a deep discharge of the lead-acid battery is not properly suitable to be used as energy reservoir to power farm household.
It can be deduced from the above analysis that the compressive loads consumed more battery energy than the non-compressive loads within 3hours of test period. It consumed averagely 508.8VAdc of battery energy per hour of use compare with non-compressive loads of 328.75VAdc. This shows that the power factor of compressive loads is greater and it can only be powered for 2hours period to keep the depth of discharge within acceptable level of 50%.
47
110
100
90
DEPTH OF DISCHARGE (%)
80
y = -21.8x + 129 R² = 0.999 70
60
50
40
30
20
10
0 0
1
2
3
TIME (hours)
Figure 4.3: DOD AGAINST TEST-TIME ON COMPRESSIVE LOAD
48
CHAPTER FIVE 5.0
Conclusion and Recommendation
5.1
Conclusion In conclusion, the inverter was designed, developed and tested. It is a 12-pulse inverter i.e.
consists of 12 IRFP 260N FETS transistors to supply electric power similar to the power grid of sinusoidal waveform and 2,024Watts transformer power output as against 2,181Watts designed for. It was tested as independent unit of power supply with forgo lead-acid battery product of 12V, 200Amperes Hour against idling; non-compressive and compressive loads. From the graphic analyses, it shows that the inverter consumed little battery energy when no load is applied; while on noncompressive loads, it consumed 54.8% of the total battery charges within 4hours of test period. 63.6% of the battery energy was consumed when on compressive loads for 3hours test period. This shows that the power factor of compressive loads is greater and the use of the lead-acid battery to supply energy to the inverter to power compressive load will drain maximum current output from it within the test period.
The disparity in the percentage of energy reservoir between the model equation results and the obtained results on the tables 4.2 and 4.3 with their graphical analyses further explained that the lead-acid battery components are deteriorating internally when is used as energy reservoir for inverter to power noncompressive and compressive loads.
We may conclude that lead-acid battery is unreliable to be used as energy reservoir to power farm household on a continuous basis and repeated deep discharges of the battery will result in capacity loss and ultimately in premature failure.
49
The 2,000Watts inverter constructed is sensitive to the low voltage power supply from PHCN and it will shut down the entire system to prevent it from malfunctioning when it is used as battery charger. The cost of production was N45, 450. The power device system was tested and found out to be functioning very well with 93% power efficiency.
5.2
Recommendation
Based on the test carried out on the inverter, the following are recommended:
i.
That further work should be carried out on the inverter by testing it on deep cycle battery i.e. it is specially designed to withstand greater degree of discharging and much less susceptible to degradation than lead acid battery.
ii.
The power device system was tested and found out to be functioning very well but further work will make it more efficient and reliable to be used in the farm households and settlements.
iii.
Sizing the inverter with battery should be based on the applied load power and battery capacity
iv.
If you are not around put off the inverter to prevent danger. This is because failure can occur in the change-over when Power Holding Company of Nigeria (PHCN) supply comes.
v.
The power of the inverter can be increased by increasing the wattage of the transformer to power heavy machines on the farm and meet future needs.
vi.
Keep away from the children because the voltage produce is lethal and can kill.
vii.
If the inverter is going to be used more than the tested period, it is advisable to increase the battery capacity to two or more by connecting them in parallel.
50
REFERENCES Bhat A.K.S. (1992): “Fixed frequency PWM series-parallel resonant converter,” IEEE Trans. Industry Applications, vol. 28, no. 5, pp. 1002–1009 Bird B.M. and King K.G. (1984): An Introduction to Power Electronics, New York: Wiley-Interscience Bose B.K. (1992): Modern Power Electronics: Evaluation, Technology, and Applications, New York: IEEE Press DBTI (Don Bosco Technical Institute Training manual) (2005): Volume 3, pp. 85-110. Don Bosco Press Harris Semiconductor (2000), User’s Guide of MOS Controlled Thyristor, CRC Press LLC http://en.wikipedia.org/wiki/Inverter (electrical) http://www.outbackpower.com Huang A.Q. (1995): Recent Developments of Power Semiconductor Devices, VPEC Seminar Proceedings, pp. 1–9 Liu K. H., Oruganti R., and Lee F.C. (1985): “Resonant Switches—Topologies and Characteristics,” IEEE Power Electronics Specialists Conference Record, pp. 106–116. Mohan N. and Undeland T. (1995): Power Electronics: Converters, Applications, and Design, New York: John Wiley & Sons Motorola, Linear/Switchmode Voltage Regulator Handbook, 2008. Olaitan, S., and Omoniyi L. (2007): Design and construction of 1000Watts automatic uninterruptible power supply for household electricity supply. Don Bosco technical college, Akure Owen, E. L. (January/February 1996). "Origins of the Inverter". IEEE Industry Applications Magazine: History Department 2 (1): pp64-66. Philips Semiconductors, Power Semiconductor Applications, 2007. PHCN (Power Holding Company of Nigeria), 2008. Marketing Department, Akure Office Rashid M. H. (1988): Power Electronics, Circuits, Devices and Applications, Englewood Cliffs, N.J.: Prentice-Hall Sukhatme, S. P. (1984): Principles of Thermal Collection and Storage. India, TATA McGraw-Hill publishing company limited, pp. 2-15 Wojslawowicz, J. (Jan. 1988): “Ruggedized transistors emerging as power MOSFET standard-bearers,” Power Technics Magazine, pp. 29–32
51
APPENDIX A
Definition of Terms
ac: Alternating current Ac: Alternating current Commutation: Process of transferring the current from one power device to another. DBTI: Don Bosco Technical Institute dc: Direct current di/dt limit: Maximum allowed rate of change of current through a device. If this limit is exceeded, the device may not be guaranteed to work reliably. DOD: depth of discharge Duty cycle: Ratio of the on-time of a switch to the switching period. dv/dt: Rate of change of voltage withstand capability without spurious turn-on of the device. Forward voltage: The voltage across the device when the anode is positive with respect to the cathode. Full-wave control: Both the positive and negative half cycle of the waveforms are controlled. I2t: Represents available thermal energy resulting from current flow. IGBT: Insulated-gate bipolar transistor. Phase-controlled converter: Converter in which the power devices are turned off at the natural crossing of zero voltage in ac to dc conversion applications. Reverse voltage: The voltage across the device when the anode is negative with respect to the cathode. SCR: Silicon-controlled rectifier.
52
APPENDIX B TRANSFORMER ANALYSIS
Design Calculation Analysis of 2000Watts Transformer. A transformer to be constructed has the following data which are: K.F = 1.05, K = 1, γ = 0.90, β = 1.1, F = 50Hz, V1= 240v, V2 = 12v, δ1 = 8A/mm2, δ2 = 8A/mm2, P1 =?, P2 =?, S1=?, S2 =?, N1 =?, N2 =?, θ1 = ?, θ2 = ?,. S.G = 70 X 70mm for lamination, and S.G = 70 X 70mm for thermoplastic. Where, S.G = length and width of the lamination
δ1 & δ2 = density
and thermoplastic,
P1 & P2= power
K = coefficient factor,
N1 & N2 = number of turns
γ = efficiency,
I1 & I2 = input & output current
β = induction of the coil,
S1 & S2 = section of the coil
F = frequency
θ1& θ2 = diameter of the coil.
V1 & V2= input & output voltage
TRANSFORMER 2000 WATTS
70
70
53
POWER CALCULATION S.G = 70 X 70mm = 4,900mm2 P1
=
2
Sg K x K.F x 100
P1
=
70 X 70
2
1 x 1.05 x 100
P1
=
4900
2
105 P1
=
(46.7)2
P1
=
2,181W
P1
=
P2 γ
P2
=
P1 x γ (VA)
P2
=
2181 x 0.9
P2
=
1963VA
in (VA)
E.M.F. Equation of a transformer & Number of turns Let N1 = Number of turns in primary side N2 = Number of turns in secondary side Φm = maximum flux in core in Webers is = Bm X A F = frequency of a.c. input in Hz
54
Cycle
Φm
T/4.f Time T =1/f Flux increases from its zero value to maximum value Φm in one quarter of the cycle i.e. in ¼ f second. Average rate of change of flux = Φm 1/4f =4 f Φm Wb/s or volt Now, rate of change of flux per turn means induced e.m.f in volts. :
Average e.m.f. /turn = 4f Φm volt
If flux Φ varies sinusoidally, then r.m.s. value of induced e.m.f. is obtained by multiplying the average value with form factor.
:
Form factor is given as
r.m.s. values Average values
=
: r.m.s value of e.m.f/turn = 1.11 X 4f Φm = 4.44 f Φm Calculation of voltage per turn e = 4.44 X f X β X s.g X 10-6 = 4.44 X 50 X 1.1 X 4900
X 10-6
= 1.1966 v/t
N1 = V1/e = 240/1.1966 = 201 turns. N2 = V2/e
55
1.11
= 12/1.1966 = 10 turns
PRACTICAL ASPECT OF DETERMINING NUMBER OF TURNS N’1 = N1 - N1 X 2.5 100 = 201 – 201 X 2.5 100 = 201 -5.025 ≈ 196 turns. N’2 = N2 + N2 X 2.5 100 = 10 + 10 X 2.5 100 = 10 + 0.25 ≈ 10 turns. I1
=
P1
=
=
P2 V2
I2
=
,
I1
=
220
V1
I2
2,181
I1
=
9.91A
I2
=
1963 12
160A
56
2,181 240
,
I1
=
9.1A
CALCULATION OF THE COIL SECTION Section S1
=
I1
(mm2)
=
δ S1
=
I1
(mm2);
=
S2
=
I2 δ2
δ1 S1
=
9.1 8
S1
=
S2
=
1.14mm2 I2 S2
S2
=
220 8
S2
=
27.5mm2 DIAMETER OF THE COIL CALCULATION
Where
θ1 =
2
S1 Π
S1 =
2
S1 3.142
S1=
2
1.13 3.142
S1 ≈
0.6mm
57
=
(mm2)
Where
S2
=
2
S2 3.142
=
S2
2
27.5 3.142
=
3mm
I1
=
P1 V1
I1
=
2,181WATTS
S2
Summary of the Inverter design
a. Transformer
OUTPUT POWER (Watts)
2,181
Number of Turns
Section of the Coil Area (mm2)
Voltage (Volts)
S1 = 1.14 S2 = 27.5
V1 = 240 V2 = 12
N1 ≈ 19 N 2 ≈ 10
c. Battery, (Lead –acid accumulator) forgo Product
Voltage
Ampere Hour
Power
12Vdc
200AH
2400VAdc
58
APPENDIX C
59
APPENDIX D Table 4.1: The result of idling load against DOD Depth of Discharge
100
99
97
95
93
0
1
2
3
4
DOD (%) Y Time (Hour) X
Table 4.2: The result of non-compressive load against DOD Depth of Discharge
100
81
69
55
41
0
1
2
3
4
DOD (%) y Time (Hour) x
Table 4.4: The result of compressive load against DOD Depth of Discharge
100
73
45
15
0
1
2
3
DOD (%) Time (Hour)
60
Table 4.3: Values of electrical properties of 2,000Watts Inverter
Designed Electrical properties
Measured values values
Nominal AC output Voltage 220Vac
220Vac
220 – 240Vac
220 – 240Vac
50Hz
49.5Hz
9.91
9.2Aac
2,181Wac
≈2,024Wac
(V) Ac operating voltage Range (V)
Nominal AC Frequency
Maximum AC output Current (I) Maximum AC output Power (IV)
Efficiency (%)
93%
61
