Design And Construction Of A 3.5KVA Modified Sine Wave Inverters

ABSTRACT

This project work is design and construction of a 3.5KVA modified sine wave inverter. Modified Square Wave or step wave approximate a pure sine waveform. The output of a modified square wave, quasi square, or modified sine wave inverter is similar to a square wave output except that the output goes to zero volts for a time before switching positive or negative Modified sine wave inverters are designed to satisfy the efficiency requirements of the photovoltaic system while being less expensive than pure sine waveform inverters. These inverters are capable of operating a wide variety of loads; electronic and household items including but not limited to TV, VCR, and satellite receiver, computers, and printers.

Some electronic devices may pick up inverter noise while operating with modified sine waveform. Using fluorescent lighting can be problematic when using modified sine wave inverters. Most of the equipment on the market is designed for use with sine waves. Some appliances, such as microwaves, drills, clocks or speed motors will not produce full output if they don’t use sine wave current, moreover they may damage the equipment. Some loads, such as light dimmers will not work without sine wave at all.

It’s safe to say any electronic device that requires sensitive calibration can only be used with pure sine wave inverters. For many electronic devices that don’t require sensitive calibration, modified sine wave inverters are a more cost-effective option.

This work is aimed at designing a 3.5KVA modified sine wave inverter that can be used to power appliances both in homes and industries.

TABLE OF CONTENTS

Title Page

Approval Page

Dedication

Acknowledgement

Abstract

Table of Content

CHAPTER ONE

1.0     Introduction

1.1     Objective of the study

1.2     Significance of the study

1.3     Inverter rating

1.5     types of inverter

CHAPTER TWO

2.0     Literature review

2.1     review of history of an inverter

2.2   review of how to choosing the right inverter

2.3      review of the difference between sine wave and modified sine wave      inverter.

2.4     review of inverter capacity

2.5     safety of inverter

CHAPTER THREE

3.0     Construction

3.1     basic designs of an inverter

3.2      block diagram of the system

3.3      modified sine wave inverter circuit using ic 3525, with regulated output and low battery protection.

3.4     description of components used

3.5     parts list

3.6      How to Choose A Right Inverter And Battery

3.7      How to choose the best inverter battery

CHAPTER FOUR

RESULT ANALYSIS

4.0     Construction Procedure and Testing

4.1     Casing and Packaging

4.2     Assembling of Sections

4.3     Testing of System Operation

4.4      Cost Analysis

CHAPTER FIVE

5.0     Conclusion

5.1     Recommendation

5.2     References

CHAPTER ONE

1.0                                        INTRODUCTION

A power inverter is a device that converts DC power (also known as direct current), to standard AC power (alternating current). Inverters are used to operate electrical equipment from the power produced by a car or boat battery or renewable energy sources, like solar panels or wind turbines. DC power is what batteries store, while AC power is what most electrical appliances need to run so an inverter is necessary to convert the power into a usable form. For example, when a cell phone is plugged into a car cigarette lighter to recharge, it supplies DC power; this must be converted to the required AC power by a power inverter to charge the phone.

In modified sine wave, The waveform in commercially available modified-sine-wave inverters is a square wave with a pause before the polarity transition, which only needs to cycle through a three-position switch that outputs forward, off, and reverse output at the pre-determined frequency. The peak voltage to RMS voltage does not maintain the same relationship as for a sine wave. The DC bus voltage may be actively regulated or the “on” and “off” times can be modified to maintain the same RMS value output up to the DC bus voltage to compensate for DC bus voltage variation.

The ratio of on to off time can be adjusted to vary the RMS voltage while maintaining a constant frequency with a technique called PWM. Harmonic spectrum in the output depends on the width of the pulses and the modulation frequency. When operating induction motors, voltage harmonics is not of great concern, however harmonic distortion in the current waveform introduces additional heating, and can produce pulsating torques.

Most AC motors will run on MSW inverters with an efficiency reduction of about 20% due to the harmonic content.

• OBJECTIVE OF THE STUDY

The objective of this project is to design and construct a modified sine wave inverter which is rated 3.5 KW which can be powered from the source of 12V battery.

This inverter is capable of operating a wide variety of loads; electronic and household items including but not limited to TV, VCR, and satellite receiver, computers, and printers.

1.3                          SIGNIFICANCE OF THE SYUDY

This study exposes me the applications and uses of a modified sine wave inverter which are as follows:

DC power source utilization

Inverter designed to provide 240 VAC from the 12 VDC source provided in an automobile. The unit shown provides more than 20 amperes of alternating current, or enough to power more than 3KW load.

An inverter converts the DC electricity from sources such as batteries, solar panels, or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage.

Uninterruptible power supplies

An uninterruptible power supply (UPS) uses batteries and an inverter to supply AC power when main power is not available. When main power is restored, a rectifier supplies DC power to recharge the batteries.

Induction heating

Modified Sine wave Inverters convert low frequency main AC power to higher frequency for use in induction heating. To do this, AC power is first rectified to provide DC power. The inverter then changes the DC power to high frequency AC power.

HVDC power transmission

With HVDC power transmission, AC power is rectified and high voltage DC power is transmitted to another location. At the receiving location, an inverter in a static inverter plant converts the power back to AC. The inverter must be synchronized with grid frequency and phase and minimize harmonic generation.

Variable-frequency drives

A variable-frequency drive controls the operating speed of an AC motor by controlling the frequency and voltage of the power supplied to the motor. An inverter provides the controlled power. In most cases, the variable-frequency drive includes a rectifier so that DC power for the inverter can be provided from main AC power. Since an inverter is the key component, variable-frequency drives are sometimes called inverter drives or just inverters.

VFDs that operate directly from an AC source without first converting it to DC are called cyclo-converters. They are now commonly used on large ships to drive the propulsion motors.

Electric vehicle drives

Adjustable speed motor control inverters are currently used to power the traction motors in some electric and diesel-electric rail vehicles as well as some battery electric vehicles and hybrid electric highway vehicles such as the Toyota Prius, BYD e6 and Fisker Karma. Various improvements in inverter technology are being developed specifically for electric vehicle applications.^[8] In vehicles with regenerative braking, the inverter also takes power from the motor (now acting as a generator) and stores it in the batteries.

Air conditioning

An inverter air conditioner uses a variable-frequency drive to control the speed of the motor and thus the compressor.

Electroshock weapons

Electroshock weapons and tasters have a DC/AC inverter to generate several tens of thousands of V AC out of a small 9 V DC battery. First the 9VDC is converted to 400–2000V AC with a compact high frequency transformer, which is then rectified and temporarily stored in a high voltage capacitor until a pre-set threshold voltage is reached. When the threshold (set by way of an air gap or TRIAC) is reached, the capacitor dumps its entire load into a pulse transformer which then steps it up to its final output voltage of 20–60 kV. A variant of the principle is also used in electronic flash and bug zappers, though they rely on a capacitor-based voltage multiplier to achieve their high voltage.

1.4    INVERTER RATINGS

The ratings that you should look at when buying an inverter (depending on the type) are:

1. Continuous Rating: This is the amount of power you could expect to use continuously without the inverter overheating and shutting down.
2. Half Hour Rating: This is handy as the continuous rating may be too low to run a high energy consumption power tool or appliance, however if the appliance was only to be used occasionally then the half hour rating may well suffice.
3. Surge Rating: A high surge is required to start some appliances and once running they may need considerably less power to keep functioning. The inverter must be able to hold its surge rating for at least 5 seconds. TVs and refrigerators are examples of items that require only relatively low power once running, but require a high surge to start.
4. IP rating – defines the ability of the inverter seals to prevent water and dust ingress. Although some inverter manufacturers claim high IP ratings suitable for outdoor installation, the quality and location of the seals and ventilation will greatly affect the ability of the inverter to outlast the many years solar installations are expected to work.
5. Peak efficiency– represents the highest efficiency that the inverter can achieve.

1.5 TYPES OF INVERTER

There are different types of inverters for home and industries available which can suit your various electricity needs. Following are the two basic types of inverters.

1. Modified Sine Wave Inverters

This type of home inverter obtains power from a battery of 12 volts and must be recharged using a generator or a solar panel. Appliances like microwave ovens, light bulbs, etc. can be run using these types of inverter.

• They can be rightly held as the best inverters for homes as they are efficient enough to provide power to the normal home requirement.
• They are the home inverters that are most affordable
• You can run the daily used home appliances using the modified sine wave home inverters.
• The electric appliances that involve motor speed controls or timers are not to be run using these types of home inverters.

The wave form of a modified sine wave inverter is as below:

2. True sine wave inverters

This is one of the better types of inverters as they provide better power as compared to the modified sine wave inverters for homes. These types of home inverter are also run using a battery of a larger capacity.

• Technically speaking, the sine waves they produce are purer, thus the
• They are best inverters employed for the power sensitive appliances like refrigerators, televisions, air conditioners, washing machines, etc.
• These types of inverters are extremely reliable. The only drawback is that they are a bit expensive and cannot be afforded by the common man.
• There are various models available based on the electricity requirement of the house.

The wave form of a sine wave inverter is as below:

3. Square wave inverter

This is the simplest form of output wave available in the cheapest form of inverters. They can run simple appliances without problem but much else. Square wave voltage can be easily generated using a simple oscillator. With the help of a transformer, the generated square wave voltage can be transformed into a value of 240VAC or higher.