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ABSTRACT

In the light of prevailing power cuts in the country, there is a sudden rise of a need to come up with backup power solutions. The most common backup supply systems available on the market are Automotive Generator Sets (convert mechanical energy to electrical energy by means of burning fossil fuel) and UPS (Uninterrupted power supply). Even though all these backup supply systems turn to perform their said functions to some extent, they turn to pose some challenges. Some of the limitations of using generator as alternative or additional source of electricity are mostly noisy during its operation, which causes disturbances in the neighborhood. The carbon mono-oxide and the black oil from the generator pose threats to the environment as air and soil or water pollutant making it non-environmentally friendly. The cost of maintenance turns to be expensive since they run on fuel, compared to an Inverter. This makes it quite unaffordable by people with low income. The 600VA DC-AC power inverter is designed to produce backup power that runs on 12V DC batteries which are ecofriendly to produce backup power for a longer period of time. This project would increase the knowledge on power inverter application by constructing a 12V DC to 220V AC with output power rating at 600VA with frequency varying between 49.95Hz, which is approximately 50 Hz. The traditional square wave derived from a stable multi-vibrator would be substituted for modified sine wave oscillator which would be designed by the combination of a timer and a flip-flop. The signal from the flip-flop is fed to a dual input Class AB pullpush amplifier to produce an alternating output with the same waveform but with a higher power enough to power up any equipment in the power rating of the system. The parallel state built by the RFP40N10 (N-Channel Mosfets) is to conduct large amount of power through the primary of the transformer to oscillate thereby generating an output at the secondary of the transformer.

CHAPTER ONE

INTRODUCTION

BACKGROUND OF THE STUDY

All modern engineering system includes certain aspects of control system at some point in their broadcast scenes, control engineering and the associated theory are concerned with the means of making system to behave in a desired may.  The system on this thesis is a DC " AC inverter which is an apparatus used in the conversion of direct current (DC) to alternating current (AC). In our contry today, this equipment is not all that in use not because it is not important but because people never give it a thought as per the construction and design. It is meant for use with a 12volts leadacid battery of it’s in a car for example a suitable output voltage of 240volts AC  obtainable.

This output voltage of 240volts AC can be used for powering small electrical appliances such as lights, electrical tools radio, soldering iron, fan etc. However,  it is with mentioning that the DC generated with this appliance is nothing comparable to the AC generated by big generation duration. This appliance is therefore suitable for short time replacement for the real AC generation especially in the remote areas and it is install where electrical appliances are sold and the need might arise for it to be tested and certified good. Another main area where this equipment can be of great utility is in communication system. In a situation where there is a constant AC power supply failure example in offices DC " AC inverter is needed and such cases, inverter can be used as a source of light.

Most industries in the country do not make use of DC " AC inverter because the are through to be costly with respect to the task they perform. However, putting into consideration the task, this appliance can perform. It can be concluded that it is cheaper. The construction is simple, cheaper, easy to operate and portable. The usefulness of this device and the function cannot be over emphasized especially now that our country is passage through a very sensitive era in our power generating Authority (NEPA) has been dubbed NEVER EXPECT POWER ALWAYS. In these times when control and monitor of complex field operations have based in computer, a failure of AC, power supply to communication equipment means work stoppage and to some small scale industries a lot of economic and materials losses is avoidable.

1.2 Statement of Problem

The most common backup supply systems available on the market are Automotive Generator Sets (convert mechanical energy to electrical energy by means of burning fossil fuel) and UPS (Uninterrupted power supply). Even though all these backup supply systems turn to perform their said functions, they turn to pose challenges. Some of the limitations of using generator as alternative or additional source of electricity are:

Noisy: Most of the automotive power generators are noisy during its operation, which causes disturbances in the neighborhood.

Environmental threat: The carbon mono-oxide and the black oil from the generator pose threats to the environment as air and soil or water pollutant making it non-environmentally friendly.

Bulky: Most generators are big plant; therefore, generation of power at remote places is not too easy.

Expensive: Cost of maintenance turns to be expensive since they run on fuel, compared to an Inverter. This makes it quite unaffordable by people with low income.

The UPS is ecofriendly but is also designed to provide backup for a short period of time, which makes it not ideal for backup systems intended to run appliances for long periods of time.

It is to this effect that the 600VA DC-AC power inverter is designed to produce backup power that runs on 12V DC batteries which are ecofriendly to produce backup power for a longer period of time. Controlling load increase or decrease backup time when energy is saved on turning off devices which are not essential. End users usually feel lazy and reluctant to go round turning of lights and other gadgets when they are not in use. With this system the user can be at one location and control appliances with a touch of a bottom.

1.3 General Objectives

The main objective of this project is to design and construct a DC to AC automatic power inverter/charger with a six channel RF based remote controlled load management switch.

1.3.1 Specific Objective

It is the goal and objective of this project to:

•  Design a modified sine wave inverter using a 555 timer as a pulse generator and TC 4013 flip-flop to drive a class B amplifier using two set of MOSFET array and a center-tapped transformer.

•  Apply new technologies in the design of power inverters/charging systems which utilizes the same transformer for the inverting of 12V DC to 230V AC and converting 230V AC to 12V DC for the charging of the battery.

•  Control the operation of the internal circuitry and the external loads with an RF based channel wireless remote control module.