DESIGN AND CONSTRUCTION OF A THREE PHASE AUTOMATIC CHANGE OVER SWITCH WITH GENERATOR STARTER AND CUT-OFF

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Public power supply is a major contributor to economic development in every nation. In developing nations like Nigeria, Ghana, Cote d’Ivoire and underdeveloped parts of the world, the public power supply for industrial, commercial and domestic use is highly unstable (Peter,2002). This has negative effect on the economy in such that most of them had to depend on frequent use of alternative power sources such as generator, inverter, solar to meet up with the energy demands. One of the common alternate sources depended on is the use of generator set which is usually connected to a changeover switch and the public power supply also connected to the switch also. The application of alternative sources of power supply is being faced with the challenge of switching smoothly and timely between the mains supply and the generator supply whenever there is power failure on the mains source and vice versa. (Ransorne,2009).

Automatic Changeover switch with generator cut off and starter is one of the electrical devices that can aid smooth switching from public supply to generator and vice versa. It automatically switches from one power source to another. When there is power failure in the public supply it starts the generator and switches to the supply (generator) and it equally switches over to the mains supply when power is restored and turns off the generator automatically. The automatic power changeover switch with generator cut off and starter is a device that links the load and mains supply or the alternative supply together. This enables the use of either the mains supply or an alternative source when there is outage on the mains source without the user intervention.

The changeover switch can either come in with three phase or single phase. This device maintains constant power supply to the load by automatically activating the generator when there is need. Since the user might not always be in need of the generator, provision has been made to prevent the generator from starting should an outage occur.

Therefore, in view of these considerations, the project aimed at designing and constructing a workable automatic change-over switch with generator cut off and starter functions.

1.2 Problem Statement

The frequent of power outages in developing countries like the case of Nigeria creates a need for automation of electrical power generation or alternative sources of power to back up the utility supply. This automation becomes important since the rate of power outage becomes predominantly high. Most industries and commercial processes are partly dependent on generators and public power supply which is epileptic especially in Nigeria. Therefore, if the processes of power change-over between these two power supplying sources are manual, human error during change-over leading to machine damage, electric shock/electrocution as well as increased down time consequently introducing massive losses. However, if the starting of the generator is automatically done by a relay which switches the battery voltage to ignition coil of the generator while the main power relay switches the load to either public supply or generator, the down time would greatly be reduce thereby maintaining the tempo of production. In view of the background, this project tends to focus on the design and construction of an automatic changeover switch with generator cut off and starter.

1.3 Aim and Objectives

This project is centered on design and construction of an automatic change-over switch with generator cut off and starter. However, the specific objectives are as follow;

1. To design a device that automatically switches on the generator and switch over the load to the generator whenever there is mains power failure.

2. To sort and examine various components to be used for the construction of automatic changeover switch.

3. To design and integrate the sub-units of the automatic changeover switch.

4. To carryout a test on the sub-units design of the automatic changeover switch.

1.4 Scope of the Study

The scope of this project is focus on designing and construction of a change-over switch with cut off and starter of a generator with the capacity of 3.5KVA. It also revolves around a project that is designed for power supply applications. It involves automatic changeover between the main power supply and an auxiliary power supply, such as a generator. The project implements an automatic switching or starting of the power generator whenever the main power fails.

1.5 Limitation of the Study

Some of the limitations of the automatic changeover design are;

1. The design cannot function with a generator that is not auto-start.

2. It does not function properly for a generator higher than 3KVA.

3. The design of the automatic changeover switch with cut off and starter does not function with a faulty generating set

4. The design will not function properly when there is no engine stopper in the generator.

1.6 Significance of the Study

The significance of this work cannot be overemphasized. Therefore, benefits that are associated to the change-over switch are;

1. It minimizes damages to lives and equipment since it has its own monitoring system and its switching requires no human contact with the switch, thus eliminating human error.

2. It reduces change-over time to a minimum, due to its fast response to power restoration

3. It maintains high quality of service through its fast and prompt response.

4. Moreover, the unit is portable, easy, convenient and safe to install.