Design and Construction of an Automatic Phase Selector

Design and Construction of an Automatic Phase Selector


Design and Construction of an Automatic Phase Selector


Abstract of Design and Construction of an Automatic Phase Selector

Automatic phase selector system is used to ensure continuous supply to load in case the mains supply is not healthy. This project is on design and construction of a three phase automatic phase selector with generator starter and cut-off. Power supply in Nigeria and most developing countries of the world is anything but stable. This has adverse effects on the consumers of the electricity and the equipments that are operated from the mains sources of electricity supply in these parts of the world. In this paper, we provide an automatic switching mechanism that transfers the consumer loads to a power source from a generator in the case of power failure in the main supply. It automatically detects when power has been restored to the mains supply and returns the loads to this source while turning off the power from the generator set. This mechanism has been tested and we recorded a great result. It thus holds an important key in the provision of a continuous power supply through an ear seamless switching between the mains supply and an alternative stand by source like the generator set.



Chapter One of Design and Construction of an Automatic Phase Selector


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 under developed 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 switchwith 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.


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.


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


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.


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.