1.1 Introduction
Electrical energy has been considered as one of the numerous form of energy and it distinguished itself vividly by the widest application in the recent years.
Electrical energy is particularly useful by reasons of the case with which it can be distributed and converted to other desired forms lighting effects, heating effect magnetic effect of electrical energy can be used to ran our inclustrus, boil our water, provide light for our homes as well as servicing and easing other human endeavours.
The wide use of electricity has necessitated the development of systems of transmission and distribution. Transmission systems are required;
- To enable sources of natural energy (e.g water fails – dams, or storage loaves, reservoirs for hydropower station, fuel fields, coal gas, diesel – for thermal generating station), for distant from the centre of energy demand (e.g large works, industrial areas of cities), to be economically utilized,
- To enable generating plant to be concentrated in a few large. Favourably situated stations; and
- To per met of the in for connection of network or distributing areas to ensure reliability economy and stability or continuity of supply.
There are three main facts in the production and utilization of electricity namely: generations transmission, and distribution generation of electrical energy employs electrical power stations. These power stations generate electrical energy making use of fuel (e.g coal, gas, diesel) as mom raw material; hence thus type is called steam or thermal power station. Other power stations make use of waterfalls or storage haves – hence called hydro electric power station: etc.
No matter the type of the power station employed, the voltage generated is usually in a low level e.g 11KV or 25KV. Owing to the distance between the centre of energy dim and (consumption areas) to the power stations, transmission system of energy times into play. A high voltage is desirable for transmitting large power in order to decrease the 12R losses and reduce the amount of conductor material. Therefore, a transformer is employed to step up the generated voltage to 3300KV/ the highest National Grid voltage although efforts are being made to increase it to 765KV for transmission. This 330KV is transmuted to the distribution ends. A very much however voltage, on the other hand, is required for distribution, for various reasons connected with safely and convenience. The transformer also mavies this easily and economically possible as the 330KV is stepped down to 132KV, 66KV, 33KV, 11KV, 415KV and to a minimum level of 240V for distribution to various load centre (consumption area).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work and Limitations of the Study.
1.2 Background of Study
The device to increase (step up) or decrease (step down) the generated voltage is called the transformer. It is a static (stationary) alternating consent machine.
Basically, transformers are classified according to purpose namely:- power transformer, distribution transformer, Auto-transformer and instrument transformer, power transformer are large transformers generally used at generating stations to step up the voltage, and at the substations to step d0wn the voltage for supplying distribution systems. They may also be used for tionving together two power stations. The power transformer has a high utilization factor, e.g it is arranged that they run with an almost constant load which is equal to their rating. The maximum efficiency is designed to be at fall load. This means that the fall-load winding losses must be equal to the here losses.
According to common usage, a transformer rated over 500KVA is termed a power transformer.
The distribution transformer has a intermittent and variable head which is usually considerable less than fall-head rating. They are therefore, designed to have their maximum efficiency at between half and three – quarter of fall head.
The instrument transformers are of two types depending on the mode of operation voltage or current transformers. The current (series) and voltage (shunt) transformers are used for extending the range of a.c. instruments in preference to shunts and series resistors.
1.3 Aim and Objectives of the Study
The aim of our study is to design and construct an auto-transformer which can step-down 240V from the local supply down to 110V, 80V, 12V, 6V. In achieving this aim, the following specific objectives of study were set out as follows
- To design and construct an electrical and electronic appliances with domestic voltage level of 110Volts.
- To investigate the cost of auto-transformer and output of this transformer is made by making numerous tapping on the primary winding depending on the required output.
- To provide information relating to the Short Circuit or Impedance Test, Construction of the Enclosure and Complete Unit, and Standard Wire Gauges and Laminations
1.4 Scope of Study
The scope of our study is committed to 1KVA auto-transformer (step down) that has these tapping as follows 110V, 80V 12V, 6V. In view of this any other thin outside this topic would not be considered.
Because of the various voltage levels on the secondary, it can be used to supply voltage to American equipment at 110V, for welding machines and electronic equipment at 12V, 6V and 80V, and for barberry charging at 6V or 12V.
1.5 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Establishment Policies: Establishment policies posed a serious limitation as most staffs are not ready to release information needed for this project work. There were lots of information needed from the staffs of this institution to enhance the study which took them time to release or they did not release at all for security purposes, hence the scope was reduced.
- Research material: availability of research material is a major setback to the scope of the study.
1.6 Definition of Terms
Transformer: A transformer is alternating current machine which is usual to increase (step-up) or decrease (step down) voltage (a.c).
Auto- Transformer: This is a transformer with single winding. The single winding is common to both the priming and the secondary of the transformer.
Winding: The winding of a transformer is the band of copper conductor which is wound into many farms on the transformer core.
Core: The core of a transformer is a pile of haminated sheets of science steel.
Turns: This is the number of times or rounds the copper conductor is wound on the core.
Lamina: This is a single sheet of the soft iron which is insulated or lamination.
Primary Winding: The primary winding of a transformer is the winding that is directly connected to the over is the winding that is directly connected to the supply.
Secondary Winding: This is the winding that is directly connected to the head.
Tappings: Tappings refers to the connections which are usually made successively in the winding of a transformer especially in auto transformer.
Step up: When the primary voltage is lower than the secondary voltage, the transformer is caved a step up transformer.
Step down: When the primary voltage is higher than the secondary voltage, the transformer is called a step down transformer.
Window: This is the space in the transformer core bounded by the 10Kes and the timbs of the transformer.
Varnish: This is an insulating Tigard which used to increase the insulation of the transformer core and winding as well as making it inechanically strong.
Copper Conductors: These are bare copper worse which are used in transformer windings.
Wire Sleeve: This can be fibre or plastic coating which is used to insulate and isolate the transformer winding terminals.
Slot Popper: This is a thick insulating paper which is used to wrap the transformer winding and separate each layer of the winding. It serves as mechanical protection.
Center Block: This is a wirden block approximately the size of the central limb of the transformer core. It is on the centre block that the former is made.
