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DESIGN AND CONSTRUCTION OF A 3-PHASEA AUTOMATIC POWER CHANGE OVER WITH GENERATOR SET SWITCHING FACILITY

CHAPTER ONE

INTRODUCTION

The evolutionary trend in industrial electronics and automation has engulfed all parts of the world and proved more challenging to as third world like Nigeria. Regarding the milestone, it was decided to make the choice of project research on the design and implementation of an automatic 3 - phase change – over with Generator switching which will eliminate the stress and lapses involved in the manual process. This electronics system is realized using 3 – phase regulated Dc power supply unit whose output is compared and fed to a 3 – input AND gate that encodes control logic to the driver stage realized using NPN Bipolar junction transistors which energize three electromagnetic relays. These relays in turn energize single coil three contacts contactors that switch the phases. (Manaha, 2008) A control/switching circuit is also integrated that takes care of the Gen set switching whenever at least one phase from mains is low/faulty.

1.1.                GENERAL DESCRIPTION OF THE PROJECT

The project design and implementation of automatic 3 – phase change – over with Gen set switching is built in several functional blocks all combined to form one functional unit. The first is made up of regulated Dc voltage power supply unit whose output is compared and fed into 74 LS11 that generates the control logic. This logic is used to bias the driver stage which energizes electromagnetic relay. These relays serve as auxiliary to a single coil 3 - contact contactor of suitable rating. The Gen set switching module incorporates delay timer and solid state relay that takes care of the process.

The project, so constructed is packaged in a plastic casing for compatibility. On the surface of the package, there are three 100k vol/pot which are used to demonstrate low voltage in a given phase. Three amber LEDs represents the mains while the three blue LEDs are for the Gen set. And these make up of the panel indicator.

1.2.          OBJECTIVES OF THE PROJECT

One of the objectives of this project is to design and construct an automatic 3 – phase change – over with Gen set switching facility which will automatically switch ON/OFF Gen set and change over between PHCN and Gen set. It is also aimed at exposing the graduating student to electronics system designing using random logic - especially in designing in industries and power electronic. Another objective of this study is to ground the graduating students in Engineering, scientific and technical writing which is indispensable in their professional practice.

1.3.  SIGNIFICANCE OF THE PROJECT

This project work signifies a lot in industrial automation and power electronics. It is very useful in wood processing industries, oil rig equipments and other manufacturing industries that used 3 – phase machines. A project of this nature can be modified to function as automatic phase selector which can be used anywhere.

1.4.  SCOPE OF THE PROJECT

This project work covers the following; transistor drivers, electromagnetic relay, contractors, 3 – input AND gate encoder, shunt regulation and comparator using Zener diode, delay/un-delay timer and other system.