CHAPTER 1

INTRODUCTION

1.1 THE BACKGROUND

Welding is a way of heating pieces of metal using electricity or a flame so

that they melt and stick together. It can simply be defined as the process of joining

two or more pieces of metal to make the act as a single piece. This is often done

by melting the work pieces and adding a filler material to form a pool of molten

material that cools to become a strong joint. Because of its strength welding is

used to join beams when constructing buildings bridges and other structures.

Welding can also be used to join pipes in pipelines power plants at the

construction sites and in home appliance. Furthermore welding is used in

shipbuilding automobile manufacturing and repair aerospace applications. There

are many kinds of welding which include arc welding resistance welding gas

welding among others. Emphasis will be laid on arc welding because it is the most

common type of welding as well as the main aim of this project.

Arc welding is the process of welding that utilizes an electrical discharge

(arc) to join similar materials together. Equipment that performs the welding

operation under the observation and control of a welding operator is known as

welding machine. To solve the problem of weight and size of conventional arc

welding machine it is necessary to design an inverter. The inverter provides much

higher frequency than 50Hz or 60Hz supply for transformer used in welding. So

transformer of much smaller mass is used to permit the handling of much greater

output power. The welding noise produce by conventional arc welding machine is

reduced by selecting the operating frequency over the hearing of human ability.

The choice of 20Khz for the inverter type arc welding machine was determined to

meet the above expectation. The output welding current is controlled by

controlling the power supply for transformer at high frequency. This power supply

is provided by a frequency inverter. Power switch IGBTs (Insulated Gate Bipolar

Transistor) or MOSFETs is used for the inverter design due to its high switching.

The control circuit use to control the output welding current is design to drive the

power switch at high frequency. Insulated Gate Bipolar Transistor power switch is

more efficient and less prone to failure than MOSFETs power switch.

1.2 AIMS AND OBJECTIVES OF THE PROJECT

The main aim and objective of this project is to design and build and arc

welding machine that operates on 36vdc at variable frequency which of benefit to

urban area. This reduces the weight and size of the transformer use for welding.

To have an arc welding machine that is more efficient which produce neat

welding.

1.3 SIGNIFICANT OF THE STUDY

The significant of this project is that it seeks to develop an arc welding

machine that is cost effective strong and portable. Not only that the arc welding

machine is strong and portable it is also mobile.

1.4 LIMITATION OF THE PROJECT

The project has certain limitations which are mentioned below.

 This project cannot weld bigger gauge of metals.

 The welding time and power depends on the battery input power.

 You are to have bands of battery for reliability when using battery.

 The machine must be used by a qualified welder. Welding can endanger the

operator or people near the working area. Therefore the performance of welding

and cutting must only be done under the comprehensive observation of all relevant

safety regulation.

 Switch function modes during welding could potentially damage the equipment. A

safety switch is necessary to prevent the equipment from electric leakage. Use

only high quality welding tools and equipment with this inverter type arc welding

machine.

1.5 PROJECT REPORT ORGANIZATION

The organization of the project report is well detailed and vast in its coverage. It

covers all the activities encountered during the research work. The first chapter is

the introductory chapter which covers the background project objectives project

justification and scope of the project.