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.
Ø This project cannot weld bigger gauge of
metals.
Ø The welding time and power depends on the
battery input power.
Ø You are to have bands of battery for
reliability when using battery.
Ø 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.
Ø 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. Chapter two presents the literature reviews.
Chapter three covers the system analysis and
design methodology in details. Chapter four presents the system implementation
which entails the circuits diagram of different stages and also the complete schematic
diagram with necessary calculation involve in the design. Chapter five is
emphasis on conclusion, problem encountered during project design,
recommendations and suggestion for further improvement. Fig1.1 depicts an
overview of project report organization.