Design And Construction Of 1.5kva Inverter

Project and Seminar Material For Electrical Electronics Engineering EEE

Abstract

This project review the conformability of uninterrupted power supply through the use of inverter. An inverter is a system that converts a direct current to an alternating current. However, inverter is of different categories base on power rating such as 1KVA, 1.5KVA,1.5KVA, 5KVA etc. Moreover, since the invention of inverter, some problem associated with alternative power supply had been drastically reduced. Meanwhile, the problems such as: noise, production of fumes, cost of procurement of oil, fuel and maintenance of plant is over.

Chapter One

1.0 Introduction

1.1 Background of the Study

The quest to convert D.C. power to A.C power to run some essential appliances results due to erratic power supply being experience. Although, between the 19th century to mid 20th century, D.C. to AC power conversion was accomplished using rotary converters or motor generator set (M-G set). In early 20th century, vacuum tubes and gas filled tubes began to be used as switches in inverter circuit. In contrast the early A.C. to D.C. converters used an induction or synchronous a.c motor directly connected to a generator (dynomo) so that the generator’s commutator reverses its connections at exactly the right moments to produce D.C.

Considering the above reasons, for the study, many electrical equipments have either developed a problem or even stopped working entirely. As a result, many businesses have been crippled thereby affecting the economy as a whole with respect to Nigeria.

Again, power disturbances occurrence are on increase resulting to high voltage spikes and momentary voltage drops, this often affect the performance of sensitive electrical electronics equipment.

Unincessant supply of electric power can not be over-emphasized in Nigeria presently, this has become the order of the day and many Nigerians now presume power outages as a normal routine in the power sector. There are factors responsible for this ugly situation such as natural disasters, vandalism, maintainability, sustainability, inadequacy and lack of vision by the political leaders to invest adequately in power sector, also absence of replacement policy resulting in absolute abandon of electrical equipment or project, unsustainable human capacity and inadequate and remuneration system to motivate human resources term to perform well on their course.

The progress made some decades ago in developing alternate source of energy has proved that independent power system are not only possible but as well practical. A wide variety of generating equipment is now available to allow individuals take advantage of any prefer renewable resources of energy. Most of these systems produce only direct current (DC) for a number of reasons and at low voltages. However, it is well known that the alternating current is the greatest and most useful form of current being generated by the power grid due to its advantages over direct current. Thus, most of the appliances and equipment are built using a.c. input source.

Therefore, there arises the need for converting direct current (DC) to an alternating current (A.C.) having a constant frequency. This process is known as inverting.

1.2 Objective of the Project

The purpose of this project is to design and construct a circuit that will take a 24V dc input from battery and produce a 200VA (AC) output at 200V – 220V, 50Hz with under voltage and over voltage protection. The study intends:

To design an electrical system that converts d.c. power to a.c. power to drive various appliances used in the laboratories, theatres, rural areas etc.
To have a source of generating electricity that has no negative effect on the environment (i.e. no greenhouse effect).
To provide an exposition to the HND students to simple electrical design, analysis and building of circuits.
To provide a noiseless and weightless source of electricity generation.
The study will also serve as a means of impacting practical knowledge and skills to students, lecturers and other who may wish to acquaint themselves with the principles of operation of an inverter system.

1.3 The Scope of Study

The scope of this study is to design and construct of an inverter system with an output power rating of 1.5KVA, maximum output current rating of 9.09A, and output voltage of 200V a.c. at 50Hz from a 24V dc input. A few most widely used applications of inverter include running of computers, microwaves and electrical power tools etc.
The scope of this project shows how low voltage d.c power supply is used to energized an inverter circuit. It also show how low a.c. voltage obtain from the oscillator output is being amplified and step up to a required output voltage.

1.4 Limitation of the Study

In spite of the construction of an inverter and its noiseless and pollution free nature unlike other alternative sources of the generating electricity, there is a need for charging and recharging the battery from time to time.

The inability of the circuit to provide a pure sine wave output from gives room for further improvement. This is because it is quite expensive to design a pure wave inverter circuit.

Again, lack of financial assistance incapacitated the project to achieve its accuracy and reliability as well its appearance (packaging).

1.5 Definition of Important Terms

Since the inverter system is an electrical/electronics system, current will flow through the various components, voltage will be dropped at some points, and therefore, the following principles were applied in designing the project.

Joule’s Law

Joule has two laws Viz:

Joule’s first law shows the relationship between heat produced by an electric current flowing through a conductor. That is the rate of heat generated (p) in a metallic conductor is directly proportional to the square of the current (I) flowing through the conductor provided that temperature is held constant

Q α I2 _____ (1)
Q = I2R _____ (2)
Q = I2Rt _____ (3)

Where Q is the amount of heat in joule, I is the electric current flowing through a conductor in ampere, R is the amount of electric resistance present in the conductor in ohm and t is the amount of time it occurs in second.
Joule’s second law: States that internal energy of a gas does not change if volume and pressure change but does change if temperature changes.

Ampere’s Law: This relates the integrated magnetic field around a closed loop to the electric current passing through the loop. Thus for any closed loop path, the sum of the length element times the magnetic field in the direction of the length element is equal to the permeability times the electric current enclosed in the loop.

Faraday’s Law of electromagnetic induction: It states that whenever there is a change in magnetic flux linked with a circuit, an emf is always induced in it and the magnitude of the induced emf is equal to rate of change of flux linkage.

e.m.f generated = (-N(“BA” ))/Δt=(-“Nd” θ)/”dt” “volts”

Lenz Law

When an emf is generated by a change in magnetic flux according to Faraday’s law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it.

The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant.

Ohm’s Law

This states that the ratio of potential difference (V) between any two points in a circuit is directly proportional to the current (I) flowing through them, provided temperature and other physical materials remain constant.

V = IR
I = V/R
R = V/I

Kirchoff’s Voltage Law

This states that the algebraic sum of voltage in each of the conductors in any closed path in a network is equal to the algebraic sum of emf
∴∑_(K=1)^n▒〖V┴-_K=0〗

Kirchoff’s Current Law

This states that the algebraic sum of currents in a network of conductors meeting at a point is zero. i.e. At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node.

Chapter Six

Summary, Conclusion and Recommendation

6.1 Summary

It is believed that the construction of 1.5KVA inverter has been done successfully. Considering the features compose in this system such as the oscillator, drivers, amplifiers and transformer stages have been taken time to design in order to achieve its set objectives. Thus, the objectives of this design and construction work is to invert D.C (direct current) energy into an A.C (altemating current) energy at 200-22OV by frequency of 50H3.

Due to difficulty and expensive cost in designing a pure since wave, the oscillator produce an a.c output modified sine wave signal within the range of 1.5-7.0v which is adjustable at 50H3 frequency. This result to the ability of the oscillator to switch at interval.

However, with the help of the drivers and amplifier, the transformer could receive signal for proper increase to a set value usually 22OV.

Without doubt, the set objectives of this design and construction work have been achieved because the inverter system can successfully convert a 24Vdc source from a battery into a 200-220V a.c sinusoidal voltage.

6.2 Conclusion

Stable power supply is very essential to all walks of life because power supply is the blood that flows through every sector and sustain it to achieve its aims. Among other alternate sources of power supply, the inverter system has proved reliable, efficient and economic wise in some of the aspect of electrical appliances. Finally, this design and construction of 1.5KVA inverter system achieved its aim with high efficiency and reliable though, there accumulates some limitations prone to it compare with commercial inverters. It has been tested and seen to be good enough for domestic use with respect to its maximum load requirement. With a 24V/75Ah d.c battery, the inverter could last for more than 8 hours if properly loaded.

6.3 Recommendation

The oscillating section of this project produces a modified sine wave which can be improved by designing the oscillator section with some additional components to give a pure sine wave form as regards to national grid generation sine wave but at a higher cost.

Also, this system can be improved by increasing the number of MOSFETS which determines the amperage of the system and lead to greater efficiency.

Again, the transformer capacity should be affected by increasing its numbers of primary and secondary windings.
The inverter should not be loaded to its fully capacity as this could damage incase of slight loading increment.

Rather, a tolerance should be provided at about 14% which helps to accommodate some systems that require heavy starting current and less current while running.

Moreover, I recommend that the system should be load with a non-resistive appliances in order to take power factor of such appliance into cognizance instead of a pure resistive load. This tends to boost its efficiency.

A battery with higher amperages should be used because it constitutes for a last longer period for the system to function.

6.4 Problem Encountered

During the course of this project a lot of challenges were met such as:

The unavailability of some components in the markets traded.
Designing of a voltage monitor circuit and its delay timing circuit.
We had challenges in connecting the components especially, the oscillator and the MOSFETS cause they are sensitive to touch but rugged when connected in the circuit.
Finally, we had difficulty in sourcing other relevant materials towards this project and the cost of acquiring them. Though, we were able to rectify all these as we can.