Table of Content

Title Page
Table Of Contents
Chapter One
1.0 Introduction
1.1 Back Ground
1.2 Aims/ Objectives
1.3 Scope Of Limitation
1.4 Definition Of Terms

Chapter Two
2.0 Literature Review
2.1 The Power Transformer
2.2 The Relay
2.3 Contactors
2.4 Switches
2.5 Capacitors
2.6 Diode
2.7 Indicator Lights (Light Emitting Diodes)
2.8 Circuit Breaker
2.9 Voltmeter
2.10 Power Supply

Chapter Three
3.0 Construction
3.1 Circuit Diagram
3.2 Block Diagram
3.3 Contactor Wiring Diagram
3.4 Diagram Of The Casing

Chapter Four
4.0 Testing And Evaluation
4.1 Testing
4.2 Evaluation
4.3 Trouble Shooting And Remedy
4.4 Maintainability

Chapter Five
5.0 Conclusion

Chapter One


As the zeal for change over on public power supply and stand-by generator increases, Engineers have researched deep into the different ways and methods of achieving power change-over both manual and automatic types.

It may not be considered a serious issue in some places where supply is up-to 90% constant or where intermittent outage causes no great damage. However, places like the business centers, industrial areas, and even cold rooms need almost 100% power supply. So in this case there is need to provide a stand-by power supply in the event of power outage. The important thing is to make sure an effective stand-by power supply which is constant and reliable is provided to eliminate the problem of long time outage.
Before, this time, changeovers are operated manually, there by making it difficult for power continuity without a time wastage. This is because an operator must always be available at any point in time. This manually operated change-over switch has two switchable positions-(main and generator) an arm is also provided from where the operator can have access to the switching. Here, the effectiveness, i.e. the fastness of the switching anytime power needs to be changed is slow, and largely depends on the operator, which means that the system will be in-effective whenever the operator is not available.

The second generation of change over switch were made semi-automatic in which the main power supply directly powers the contactors. This arrangement is made in such a way that if the main power supply fails, the contactors will all drop, leaving the supply to the generator position. The effectiveness of the system will now depend on the operator to start the generator on time.

The main problem suffered by the manual and semi-automatic systems is that the operator must have to be continuously be on duty for it to be very effective. This depends on fully closed loop system to operate.
With more research by the scientists and engineers to improve on the earlier ones, the present day technology has made it possible for the change over switch to be more effective and fast with less labour more improvements has be made in terms of number of designs, using the closed loop system at feed back control. Some also use comparators, logic circuits and electronics timers to achieve the task.

The design of this project is in such a way that control or switching is done without any noticeable sign. It uses a combination of comparators digital switches (relays) and electromagnetic switches to achieve a very fast and effective change-over in the case of power failure. This type of switch does not depend on any operator to function well.


The background to this project work is traced to the in tense demand of the populace and industries, residential homes, and many more demand for change of power supply switch for effective and continuity of power supply without a notice interruption or delay in such process to any alternative supply if the main supply goes off.

Earlier to this time, such process is manually operated or not in used at all. The manual type which is always strenuous and time delayed was a little bit useful but not to a satisfactorily level. More level and expenses are always required to meet up with the time factor and effectiveness required of this process of change over. These expenses and labour could not be afforded by some individuals and industries that needed to practice this change over.

Regard to this solutions were suggested to improve the process, so the idea of change or transforming the manual operated to automatic was discovered and engineers went into work immediately and came up with this automatic change over switch. But the demand for this equipment was much that something must be done to meet up with increasing demand. But this increase in demand topples the decrease in supply due to the cost of securing this equipment. The students went into this project to find out how mass production could reduce the increase in demand or meet up with the demand. They now decide to go further single handedly produce this work and see how far it can be done without the help of industrial machine.
After the approval, we went into market survey and evaluation of the components, after a good study of the circuit diagram. The rating of the equipment was also considered. A lot of considerations were made based on the fluctuating nature and inconsistency of our main supply source. The cost of procuring the system was put together and found out that it is less cost, and easy in operation. The users can experience change over supply without an input or extra labour.

With all these considerations and studies we decided to put together this project.


The primary aim and objective of this project work among other things are:
a) To see how the problems of power change over can be solved with less capital and less labour.
b) To make sure that an average person can reach to the equipment by the evaluation of the cost of production of this project.
c) To check the effectiveness of this work and how fast it can work without risk or extra labour or shock to personnels.

It is also aimed at improving the availability of power supply at any point in time with this equipment, due to its automatic nature. This is because the automatic nature of this project makes it un noticeable at the out put or at the load.

This equipment when used will solve the problem of power outage suffered or delayed in change over suffered by many industries and business centres where power failure are greatly felt, and can cause a lot of regrets, because information are lost severally because of power failure, especially in business centres. This work therefore remedies these problems but can be regrettable.


The scope or range of this project work is as wide as 2.5KVA as the rating. This means that it is capable of with standing any input of the range from any source especially generator sets and can give an output of 220-230Volts.

With this rating of 2.5KVA and a voltage of 230Volts, this work can stand any load.

The limitation is within prescribed output /input range. In other words any increase in the input could cause some damage to the components.

Again, a circuit breaker was provided to protect the circuit from damage due to voltage surge or output fault or load fault.

The current rating is of 10.9Amps which is enough to withstand any load within the range.


Generally, a change over switch is a system which could be manually or automatically operated, that changes one source of power supply to another source in the case of failure from either of the two sources.