Design and construction of a 60amp three phase automatic changeover switch

Project Abstract

<p> The design and construction of a 60A, 3-Ф automatic power changeover from public utility supply to generator and vice versa was aimed at providing a useful system for use in our homes or offices. The system was achieved with a 66A 3-Ф contactor, 100mA transformers and relays. The system turns on a generator when the public utility (PHCN) is off by cranking the starter and a provision was made to stop cranking when the generator is fully started. A delay was provided to stop the generator five minutes after the PHCN is restored to avoid unnecessary off and on. A display that shows when PHCN or GEN is on was provided. <br></p>

Project Overview

<p> </p><p>COVER PAGE……………………………………………………………i</p><p>TITLE PAGE …………………………………………………………..…ii</p><p>APPROVAL PAGE…………………………………… …………………iii</p><p>DEDICATION …………………………………………………………….iv</p><p>ACKNOWLEDGEMEN ………………………………………………. …v</p><p>ABSTRACT………………………………………………………………..vi</p><p>TABLE OF CONTENTS…………………………………………………..vii</p><p><b>CHAPTER ONE: </b>INTRODUCTION………………………1</p><p>1.1 BACKGROUND OF STUDY……………………………………………1</p><p>1.2 AIMS AND OBJECTIVE………………………………………………..2</p><p>1.3 RELEVANCE OF THE STUDY…………………………………………3</p><p>1.4 SCOPE OF THE PROJECT………………………………………………4</p><p>1.5 STATEMENT OF THE PROBLEM………………………………………5</p><p>1.6 IMPORTANCE OF THE STUDY…………………………………………7 viii</p><p>1.7 PROJECT REPORT ORGANIZATION…………………………8</p><p><b>CHAPTER TWO: </b>LITERARTURE REVIEW…………………..……………9</p><p>2.1 HISTORICAL BACKGROUND…………………………………….9</p><p>2.2 DISCRIPTION OF COMPONENTS USED ………………………………13</p><p>2.3 CONTACTOR………………………………………………………… …13</p><p>2.3.1 OPERATING PRINCIPLES………………….………………………….15</p><p>2.3.2 APPLICATIONS…………………………………….……………………17</p><p>2.4 RESISTORS………………………………………………………………..18</p><p>2.4.1a USES OF RESISTORS………………………………………………….19</p><p>2.4.1b TYPES OF RESISTORS………………………………………………19</p><p>2.4.1c FIXED RESISTORS……………………………………………………20</p><p>2.4.1d VARIABLE RESISTORS………………………………………………20</p><p>2.5 CHARACTERISTICS OF RESISTORS…………………………………….21</p><p>2.6 CAPACITORS……………………………………………………………….21</p><p>2.6a TYPES OF CAPACITORS ………………………………………22 ix</p><p>2.6b USES AND APPLICATION OF CAPACITORS…………………………..22</p><p>2.7 TRANSFORMERS……………………………………………………………23</p><p>2.7a USES OF TRANSFORMER…………………………………………………25</p><p>2.8 RELAYS………………………………………………………………………25</p><p>2.8a TYPES OF RELAYS………………………………………………………..26</p><p>2.8b FACTORS TO CONSIDER BEFORE SELECTING A RELAY…………..27</p><p>2.8c APPLICATION OF RELAY………………………………………………..28.</p><p>2.9 DIODES………………………………………………………………………28</p><p>2.9a USES OF DIODES………………………………………………………….29</p><p>2.10 CRYSTAL OSCILLATORS………………….………………………………29</p><p>2.10a TYPES OF CRYSTAL OSCILLATORS……………………………………29</p><p>2.10b TERMS ASSOCITED WITH CRYSTAL OSICLLATORS……………….30</p><p>2.1Oc APPLICATION AND USES OFF CRYSTAL OSCILLATORS…………31</p><p>2.11 REGULATORS………………………………………………………………31</p><p>2.11a APPLICATION AND USES OF REGULATOR……………………….…32 x</p><p>2.12 TRANSISTORS……………………………………………………………..32</p><p>2.12a TYPES OF TRANSISTORS……………………………………………….33</p><p>2.12b USES OF TRANSISTORS…………………………………………………33</p><p>2.13 PROGRAMMABLE INTERFACE CONTROLLER (PIC)………………..34</p><p>2.14 SEVEN SEGMENT DISPLAY (SSD)………………………………………35</p><p><b>CHAPTER THREE: </b>SYSTEM OPERATION……………….………………..37</p><p>3.1 BLOCK DIAGRAM AND OPERATION……………………………………37</p><p>3.2 CIRCUIT DIAGRAM AND OPERATION………………………………….44</p><p><b>CHAPTER FOUR: </b>CIRCUIT DESIGN AND OPERATION………………….48</p><p>4.0 CIRCUIT DESIGN AND OPERATION………….………………………….48</p><p>4.1 CHOICE OF CONTACTOR………………………………………………….48</p><p>4.2 CHOICE OF TRANSFORMER………………………………………………48</p><p>4.3 CALCULATION FOR RECTIFICATION……………………………………49</p><p>4.4 GENERATOR TURNOFF DELAY…………………………………………..50</p><p>4.5 COMPLETE DESIGNED CIRCUIT OF THE DISPLAY AND CONTROL……………………………51 xi</p><p>4.6 CALCULATION FOR THE SEVEN SEGMENT TRANSISTOR SWITCHING……………………55</p><p>4.7 CURRENT DEMAND FOR THE DISPLAY UNIT…………………………55</p><p>4.8 DISPLAY PROGRAM SOURCE CODE………….…………………………56</p><p><b>CHAPTER FIVE</b></p><p>5.1 TESTING, RESULT AND PROJECT COSTS………………………………60</p><p>5.2 TESTING……………………………………………………………………..60</p><p>5.2a VOLTAGE TESTS…………………………………………………………..60</p><p>5.2b RESISTANCE TESTS………………………………………………………61</p><p>5.2C OPERATION TESTS……………………………………………………….63</p><p><b>CHAPTER SIX</b></p><p>6.1 CONCLUSION……………………………………………………………..67</p><p>6.2 RECOMMEDATION……………………………………………………….70</p><p><b>REFRENCES…………………………………………………………………….71 </b>xii</p><p><b>LIST OF FIGURES</b></p><p>Figures pages</p><p>Contactor symbol…………………………………………………………….. 15</p><p>Symbol of a fixed resistor ……………………………………………………..20</p><p>Symbol of a variable resistor …………………………………………………..21</p><p>Symbol of a capacitor ………………………………………………………….22</p><p>Transformer and its winding …………………………………………………..24</p><p>Symbol of a relay ……………………………………………………………….26</p><p>Diode symbol …………………………………………………………………..28</p><p>Oscillator ……………………………………………………………………….29</p><p>Regulator ……………………………………………………………………….32</p><p>Pic (16f8676A) …………………………………………………………………34</p><p>Seven segment symbol …………………………………………………………35</p><p>555 timer symbol ………………………………………………………………36</p><p>Block diagram …………………………………………………………………37 xiii</p><p>Circuit diagram ……………………………………………………………….43</p><p>System display flowchart ……………………………………………………..46</p><p>Step down transformer rating (windings) …………………………..……… .48</p><p>Rectification circuitry………………………………………………………… 49</p><p>Delay circuitry …………………………………………… …………… …….50</p><p>Seven segment display and controller circuitry………………….53</p><p>Display/transistor switching circuitry……54</p><p><b>LIST OF TABLES</b></p><p>TABLES pages</p><p>Summary of performance evaluation…… 40</p><p>Project cost /BEME (bill of engineering measurement and evaluation)…………65</p> <br><p></p>