Design And Construction Of A 4.8Kw Pure Sine Wave Inverter (3Rd Edition)

ABSTRACT

This study is on design and implementation of a sine wave inverter circuit developed to run AC appliances at a low cost which high efficiency. The design consists of two stages i.e. the DC-DC step up stage and a DC-AC Inverter stage. The DC-DC step up converter is based on a push-pull design to step 24 VDC to 300 VDC. Pulse width modulation was used i.e. the SG3525 pulse width Modulator. The DC-AC inverter stage comprised of four power MOSFETS in an H-bridge configuration, driven by a 40 kHz square wave encoded/modulated by a 50 Hz sine wave that was derived from a TL084 quad op amp sine wave oscillator. An output voltage range of about 240-260 VAC from 300 VDC input was obtained. A low pass filter was used to filter out the high frequencies and thus isolate the harmonics so a 50 Hz fundamental frequency was retained.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1     BACKGROUND OF THE PROJECT

• PROBLEM STATEMENT
• AIM AND OBJECTIVES OF THE PROJECT
• SCOPE OF THE PROJECT
• RESEARCH QUESTIONS
• ADVANTAGES OF SINE WAVE INVERTERS
• PROBLEM/LIMITATION OF THE STUDY

CHAPTER TWO – LITERATURE REVIEW

2.1     OVERVIEW OF AN INVERTER

2.2    INPUT VOLTAGE OF AN INVERTER

2.3    OUTPUT WAVEFORM OF AN INVERTER

2.4      INVERTER OUTPUT FREQUENCY

2.5      INVERTER OUTPUT VOLTAGE

2.6      INVERTER BATTERIES

2.7      APPLICATION OF INVERTER

2.8      COMPARISON OF PURE SINE WAVE OVER MODIFIED SINE WAVE INVERTER

2.9    REVIEW OF RELATED STUDY

2.10  REVIEW OF EARLY INVERTERS

CHAPTER THREE – RESEARCH METHODOLOGY

• POWER SUPPLY AND TRANSFORMER SELECTION
• DC-AC INVERSION
• H-BRIDGE
• BATTERY
• THE MAIN
• FEEDBACK
• BATTERY SENSE
• OVERLOAD SENSE

CHAPTER FOUR

4.1     RESULT AND DISCUSSION

CHAPTER FIVE

5.1     CONCLUSION

REFERENCES

CHAPTER ONE

1.0                                          INTRODUCTION

1.1                             BACKGROUND OF THE STUDY

Electricity is one of the greatest inventions man has ever made, due to its very important role in socio-economic and technological development (Owen et al, 2016). Electricity can be transmitted in two different ways namely: alternating currents (AC) or Direct current (DC). Alternating current is the form obtained from power outlets in homes and offices. It consists of a sinusoidal voltage source in which a continuous change in the direction of flow of voltage (and current) can be used to employ magnetic components (Cooks et al., 2011). Direct current is electricity flowing in a constant direction, and/or possessing a voltage with constant polarity and is appropriate for short-range transmission. Direct current is the form stored up in batteries. It uses is limited and it depends on AC power (Owen et al, 2016) .

A common difference between AC and DC involves the amount of energy that each can carry. Direct current has a voltage level and cannot travel very far until it losses energy. Ac is safer to transmit over long distance (Nergaard et al., 2011). DC is preferred over AC because of its portability hence the introduction of the inverter that are mobile AC source from a portable DC battery. An inverter is an electrical device that converts DC to AC; the converted AC can be at any required voltage frequency with the use of appropriate transformers, switching and control circuits. There are three types of DC-AC inverters, the square wave, the modified sine wave and pure sine wave.

Pure sine wave inverters are the most affluent in terms of efficiency and accurate timing output. They use batteries to generate power and it’s important to have a means of recharging (Cunningham, 2019). Various methods can be adopted such as solar panels, wind turbine etc. Pure sine wave inversion is obtained by taking a DC voltage source and switching it across a load using an H-bridge. If this voltage needs to be boosted from the DC source in the inverter, it can be accomplished either before the AC stage by using a DC-DC boost converter, or after AC stage by using a Boost transformer (Crowley et al., 2011). The inverted signal is composed of a pulse width-modulated signal which encodes a sine wave. The duty cycle of the output is changed such that power transmitted is exactly that of a sine wave. This output can be used as it is or,  alternatively,  can be filtered easily into a pure sine wave (Nuzhat et al., 2010) .

This report documents the design of a pure sine wave inverter, focusing on the inversion of a DC high voltage source (Gurdjian et al., 2010). The various applications of the inverter are Wind/solar electrical systems, Back-up for power cells, Generator support systems, Remote homes, Telecommunications, Computers, Tools, Security applications, Mobile power, Boats and yachts, Airplane, Monitoring equipment, Emergency power and lighting etc.

1.2                                     PROBLEM STATEMENT

Pure sine wave inverter was introduced or invented to overcome problems noticed on modified wave inverter such as rough changing phase angle and odd harmonics which makes it difficult and dangerous to be used with some selected loads (such as inductive loads).

In sine wave inverter:

1. The output wave-form is a sine-wave with very low harmonic distortion and clean power like utility supplied electricity.
2. Inductive loads like microwaves and motors run faster, quieter and cooler.

• Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, fax and answering machines.

1. Prevents crashes in computers, weird print outs and glitches in monitors

1.3                      AIM AND OBJECTIVES OF THE STUDY

The main aim of this work is to build an inverter whose output wave-form is a sine-wave with very low harmonic distortion and clean power like utility supplied electricity.

The objectives of this work are:

1. To fabricate a pure sine wave inverter with available low cost components
2. To build a circuit whose output is sine wave with low harmonics

• To provide solution to erratic nature of power supply in developing country.

1.4                                      SCOPE OF THE STUDY

The scope of this work covers generating a sine wave form that will be used to converts DC power (batteries, accumulators) into alternating current (typically 220 volts 50 Hz sine). The conversion stage of this device is two stages: DC-DC step up stage and a DC-AC Inverter stage. The DC-DC step up converter is based on a push-pull design to step 24 VDC to 300 VDC. Pulse width modulation was used i.e. the SG3525 pulse width Modulator. The DC-AC inverter stage comprised of four power MOSFETS in an H-bridge configuration, driven by a 40 kHz square wave encoded/modulated by a 50 Hz sine wave that was derived from a TL084 quad op amp sine wave oscillator.

1.5                                     RESEARCH QUESTIONS

At the end of this work answers to the following questions shall be provided:

1. How a sine wave is obtained from an inverter?
2. What is sine wave inverter?

• How can I make my own inverter?

1. What are sine wave inverters used for?
2. Is a pure sine wave inverter more efficient?
3. Why are pure sine wave inverters so expensive?

1.6                  ADVANTAGES OF SINE WAVE INVERTERS

1. The output wave-form is a sine-wave with very low harmonic distortion and clean power like utility supplied electricity.
2. Inductive loads like microwaves and motors run faster, quieter and cooler.

• Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, fax and answering machines.

1. Prevents crashes in computers, weird print outs and glitches in monitors

1.7                     PROBLEM/LIMITATION OF THE STUDY

Too complex and expensive: due to the use of multiple circuits to generate sine wave form made the device more complex and expensive than the modified sine wave inverter.

Higher dc voltage: due to push-pull circuit involved, most of sine wave inverter uses 24v instead of normal 12v others are using.