Description
ABSTRACT
The project presents here is on design and construct a single phase auto-transformer of rating 1kva, and step down voltage of 240v and voltage taps of 120, 48, 24v, 12v.
An auto-transformer is an electrical transformer with only one winding. In an auto-transformer portions of the same winding act as both the primary and secondary. The winding has at least three taps where electrical connections are made. Auto-transformers have the advantages of often being smaller, lighter, and cheaper than typical dual-winding transformers, but auto-transformers have the disadvantage of not providing electrical isolation.
The ain of this work is to build a 1kw auto-transformer with step down voltage of 240v and voltage taps of 120, 48, 24v, 12v.
TABLE OF CONTENT
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
TABLE OF CONTENT
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE PROJECT
1.2 PROBLEM STATEMENT
1.3 AIM OF THE PROJECT
1.4 SIGNIFICANCE OF THE PROJECT
1.5 LIMITATION/PROBLEM OF THE PROJECT
1.6 APPLICATION OF THE PROJECT
1.7 PURPOSE OF THE PROJECT
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 REVIEW OF TRANSFORMER HISTORY
2.2 REVIEW OF TYPES OF TRANSFORMER
2.3 REVIEW OF CLASSIFICATION OF TRANSFORMER
2.4 REVIEW OF IMPORTANCE OF DIFFERENT KINDS OF TRANSFORMER COOLING SYSTEM
2.5 REVIEW OF MAINTENANCE OF TRANSFORMER COOLING SYSTEM
CHAPTER THREE
3.0 CONSTRUCTIONS
3.1 AUTO-TRANSFORMER BASICS
3.2 OPERATION OF AUTO-TRANSFORMER
3.3 AUTO-TRANSFORMER DESIGN
3.4 AUTO-TRANSFORMER CONSTRUCTION
3.5 DESIGN CALCULATION
CHAPTER FOUR
4.0 RESULT ANALYSIS
4.1 ASSEMBLING OF SECTION AND TESTING
4.2 TESTING OF SYSTEM OPERATION
4.3 PROBLEMS ENCOUNTERED
5.4 COST ANALYSIS
CHAPTER FIVE
5.1 CONCLUSION
5.2 RECOMMENDATION
5.3 BIBLIOGRAPHY
CHAPTER ONE
1.0 INTRODUCTION
| 1.1 BACKGROUND OF THE PROJECT
An auto-transformer has its primary and secondary connected to each other electrically. A portion of the energy in an auto-transformer comes from this connection while the balance comes directly from the supply. Building inspectors often object to auto transformers because they do not isolate one circuit from the other. One ground may be at a considerably higher voltage than the ground in another section of the same circuit. Local inspectors and utility companies should be consulted before installing auto-transformers(Paul et al., 2019). Where the use of auto-transformers is not objectionable, they do represent a considerable saving in price over that of a regular separate winding transformer. This saving varies as the ratio of windings changes. After the ratio of windings reaches approximately 4:1 or 5:1, there is very little economy in using an auto-transformer. Auto-transformers are most practical where a small percentage of voltage raising or lowering is required and isolation between the two circuits is not required (Paul et al., 2019). |
In an auto-transformer, portions of the same winding act as both the primary and secondary sides of the transformer. The winding has at least three taps where electrical connections are made. Auto-transformers have the advantages of often being smaller, lighter, and cheaper than typical dual-winding transformers, but auto-transformers have the disadvantage of not providing electrical isolation (Pansini, 2019).
Auto-transformers are often used to step up or step down voltages in the 110-115-120 volt range and voltages in the 220-230-240 volt range—for example. Providing 110 or 120V (with taps) from 240V input, allowing equipment designed for 100 or 120 volts to be used with a 240 volt supply. But in this project a step down voltage of 240v as the primary voltage and 120, 48, 24v, 12v was designed.
1.2 PROBLEM STATEMENT
multiple-winding transformers are always require much copper winding, for this reason they are always heavy, expensive and bulky. To overcome this problem an auto-transformer was invented. Auto-transformer uses fewer windings and a smaller core, an auto-transformer for power applications is typically lighter and less costly than a two-winding transformer, up to a voltage ratio of about 3:1; beyond that range, a two-winding transformer is usually more economical(Pansini, 2019).
In three phase power transmission applications, auto-transformers have the limitations of not suppressing harmonic currents and as acting as another source of ground fault currents. A large three-phase auto-transformer may have a “buried” delta winding, not connected to the outside of the tank, to absorb some harmonic currents.
In practice, losses mean that both standard transformers and auto-transformers are not perfectly reversible; one designed for stepping down a voltage will deliver slightly less voltage than required if it is used to step up. The difference is usually slight enough to allow reversal where the actual voltage level is not critical(Pansini, 2019).
Auto-transformers use time-varying magnetic fields to transfer power. They require alternating currents to operate properly and will not function on direct current.
1.3 AIM OF THE PROJECT
The aim of this work is to build a 240v auto-transformer with step down voltage of 240v/110, 80, 12v, 6v.
1.4 PURPOSE OF THE PROJECT
The purpose of this work is to construct a transformer with only one winding wound on a laminated core. In auto transformer, the primary and secondary winding are interrelated. A part of the winding is common to both primary and secondary sides. On load condition, a part of the load current is obtained directly from the supply and the remaining part is obtained by transformer action
1.5 SIGNIFICANCE OF THE PROJECT
- The auto transformer can increase the voltage a bit. The auto transformer can also decrease the voltage by a bit if that is what is needed.
- For transformation ratio = 2, the size of the auto transformer would be approximately 50% of the corresponding size of two winding transformer. For transformation ratio say 20 however the size would be 95 %. The saving in cost of the material is of course not in the same proportion. The saving of cost is appreciable when the ratio of transformer is low, that is lower than 2. Thus auto transformer is smaller in size and cheaper.
iii. An auto transformer has higher efficiency than two winding transformer. This is because of less ohmic loss and core loss due to reduction of transformer material.
- Auto transformer has better voltage regulation as voltage drop in resistance and reactance of the single winding is less.
1.6 LIMITATION OF THE PROJECT
An auto-transformer does not provide electrical isolation between its windings as an ordinary transformer does; if the neutral side of the input is not at ground voltage, the neutral side of the output will not be either. A failure of the insulation of the windings of an auto-transformer can result in full input voltage applied to the output. Also, a break in the part of the winding that is used as both primary and secondary will result in the transformer acting as an inductor in series with the load (which under light load conditions may result in near full input voltage being applied to the output). These are important safety considerations when deciding to use an auto-transformer in a given application.
1.7 APPLICATIONS OF AUTO-TRANSFORMER
- Compensating voltage drops by boosting supply voltage in distribution systems.
- Auto transformers with a number of tapping are used for starting induction and synchronous motors.
- Auto transformer is used as variac in laboratory or where continuous variable over broad ranges are required.
CHAPTER FIVE
5.1 CONCLUSION
Seeing as how we can tap any transformer winding to obtain the equivalent of several windings (albeit with loss of electrical isolation between them), it makes sense that it should be possible to forego electrical isolation altogether and build a transformer from a single winding. Indeed this is possible, and the resulting device is called an autotransformer
Autotransformers find popular use in applications requiring a slight boost or reduction in voltage to a load. The alternative with a normal (isolated) transformer would be to either have just the right primary/secondary winding ratio made for the job or use a step-down configuration with the secondary winding connected in series-aiding (“boosting”) or series-opposing (“bucking”) fashion. Primary, secondary, and load voltages are given to illustrate how this would work.
5.2 RECOMMENDATION
This project is designed to be used in homes and industries and wherever the need for power distribution and consumption is needed. And should be used and maintain by a qualified personnel.
