Design And Construction Of An Automatic Changeover Switch Between Mains Supply And Inverter

ABSTRACT

This work is on change over selector switch for automatic toggling OFF of a solar inverter when AC mains is present and vice versa and also the system must enable automatic switching of the battery charger such that when AC mains is present the inverter battery gets charged (during sunset) and when AC mains fails, the battery gets connected with the inverter for supplying AC to the load. The configuration should be such that everything takes place automatically and the appliances are never switched OFF, just reverted from inverter AC to Mains AC and vice versa during mains power failures and restorations.

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

This automatic inverter Changeover Switch is a device used to switch on/off a power supply and subsequently switch on another power supply. Basically it is aimed at switching on a more convenient power supply to the load. This work offers automatic toggling of an inverter when AC mains is present and vice versa and also the system must enable automatic switching of the battery charger such that when AC mains is present the inverter battery gets charged and when AC mains fails, the battery gets connected with the inverter for supplying AC to the load.

Since it switches on power to the load, precautions has to be taken while choosing the type of Change Over Switch, while selecting the appropriate size, the control of arcing has to be put into consideration.

A good switch should be the one whose contact is made in such a way as to limit the arc formation by having no contact-bounce and by having contacts made of good conductive, corrosion resistance and wear resistance materials.

A good change over switch must have adequate insulation and must be so constructed and located as not to constitute a potential hazard.

A good change over switch should also have tight contact points so as to limit or eliminate the possibility of partial contact at the contact point. The partial contact leads to overheating of the components and may lead to fire outbreak in the entire room.

1.2                                                  PROBLEM STATEMENT

Due to inconsistent supply of power, there is a growing need for an alternative source of power supply that is the major reason of having inverter. This has lead to heavy capital investment in a bid to suppress power failure and ensure regular power supply for the industry, hospitals, schools and homes. The problem of power failure can be checkmated with the use of stand-by inverter system.

If some of these big firm do not make provisions for stand-by power source, frustration could set in which may lead to the closure of business and thus throwing workers into unemployment. Also in the case of hospital, undergoing a surgical operation and power supply suddenly go off, the patient might loose his or her life due to the power outage.

In the last decay, switching from mains supply to inverter and vice –versa is done manually, and this involves labour, wastes time and at the same time can expose the operator to risk of electric shock. However, this device was invented to solve this problem, it switches automatically between the mains supply and solar inverter when the need arise.

1.3                                                 AIMS AND OBJECTIVES

This project is aimed at designing and constructing a workable automatic change over switch for an inverter which offers automatic toggling of an inverter when AC mains is present and vice versa. The objectives of the work are:

1. To build the system prototype
2. To provide a means of having uninterruptible power supply in our home, office, workshops or industries

• To reduce the risk of electric shock and human labour

1.4                                         SIGNIFICANCE OF THE PROJECT

The automatic change over switch, the switch aimed at achieving the following automatic actions;

• To change power over from inverter to mains supply and vice-versa and also to enable automatic switching of the battery charger such that when AC mains is present the inverter battery gets charged and when AC mains fails, the battery gets connected with the inverter for supplying AC to the load.

The automatic change over unit can be operated in single inverter has the following advantages;

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

It reduces its change over timing to the minimum due to its fast response to power outage.

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

Moreover, the size and captivity of the unit will depend upon the load for which it will be used. The unit is also portable, easy, convenient and safe to install.

1.5                                        LIMITATION OF THE PROJECT

In the course of designing this project, different kinds of problem was notice such as:

• Difficulty in troubleshooting with circuit without the circuit diagram
• Difficulty in connecting the output without short-circuiting, until a multiplexing circuit was gotten.
• Difficult in wiring because of the strong wiring the project required..

1.6                              SCOPE AND LIMITATION OF THE STUDY

This work covers only a one phase automatic changeover which can only be used for providing a means of switching from inverter to AC mains and vice- versa in the case of failure in public utility.

1.7                                         APPLICATIONS OF THE PROJECT

1. Apart from using this work in solar inverter, this circuit can also be used as a home lighting system with few modifications.
2. It can be used to drive other DC loads like a DC motor of any electronic appliance or other toy applications.

1.8                                                        METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the changeover was carried out.
2. Studying of various component used in circuit.
3. Construct a changeover circuit.

• Finally, the whole device was cased and final test was carried out.

1.9                                       PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied,  chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.