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DESIGN AND CONSTRUCTION OF AUTOMATIC CHANGE OVER SWITCH WITH INDICATOR

ABSTRACT

This project work deals on the design and construction of an automatic power changeover that will change/transfer control from MAINS to Gen set and can switch ON/OFF the Gen automatically. The system integrates phase selector in MAINS and changeover to Gen. It is designed in several blocks all combined to from one functional unit. A +5v regulated DC power supply unit forms the first block whose output is fed to priority encoder and decoder block. The output of the BCD – Decimal decoder is used to select the phase in priority through a transistor driver stage and electromagnetic relay that activates contactors. The least prioritized phase is the Gen set which contains a circuitry that automatically starts and stops the Gen set. The system is realized with TTL chips market. LEDs and AC panel lamps are used to indicate the status of the system while a manual switch is used to demonstrate the mode of operation of the system.

CHAPTER ONE

INTRODUCTION

1.1.  BACKGROUND OF THE STUDY

Industrial automation and control has contributed immensely to the high rate of the world’s technological growth. Power control and automation is a part of this field which is applied in virtually anywhere electrical power is used, generated or transmitted. Manual power change-over switches have been in existence and in different forms and shapes. 1959, the advent of microelectronics has paved way to modify the manually operated change-over switches. This project deals with the design and construction of automatic change-over switch with indicator. It eliminates the time and energy spent in operating the manual change – over and starting of Gen. Set. It is fully automated. It can be used in residential houses, offices and most importantly, in factories that required constant power supply. It has so many advantages over the existing ones/types.

This project work is embarked upon to eliminate nearly every shortcomings associated with the manually operated type to ensuring that it is fully automated. This system is realized in several functional blocks all combined to form one functional system. The first block is a 3-phase MAINS regulated dc power supply unit that powers the overall circuit and acts as the input. The output of thin block is fed into a priority encoder (74147) which selects the most prioritized phase at a time. The third block is a BCD – to – DECIMAL Decoder (7442) used to decode the prioritized phase.

The fourth is the driver stage which comprises of NPN transistor that energizes the electromagnetic relay which switches the phase in priority. The Gen set switching section is achieved using the least prioritized phase. This section switches ON the Gen set when all the NEPA phases are low, OFF or faulty. Once the Gen set phase is selected, a switching transistor fires an SCR which conducts large battering current to the ignition coil of the Gen set. Panel indicators are used to show the status of the system.

1.2. OBJECTIVES OF THE STUDY

The major objectives of this project is to design and construct an automatic change-over switch with Gen set switching facility capable of transferring control from MAINS to Gen set.

It is also aimed at equipping the graduating student with Hands – on experiences which is invaluable in their professional practice.

It is aimed at grounding the graduate of EEE in electronic system designs involving power control and automation using random/Hard wired logic.

Another objective of this project is to acquaint the graduating students on the ethics of Engineering, technical and scientific writing which is a nucleus of engineering professional practice.

1.3.  SIGNIFICANCE OF THE STUDY

This project work signifies a lot in Electrical power control and automation. It means a lot in EEE. This project is a design that has to be developed and funded for commercial purposes regarding its usefulness. This project eliminates the stress, time delay and other drawbacks in manually operated types. The project can be modified to display the phase in use at a particular time using a single seven segment Display and its appropriate circuitry. It also exposes the students to digital system designs involving Encoders & Decoders.

1.4.  SCOPE OF THE STUDY

This project work focuses on the design and construction of automatic change-over switch with Gen set switching facility. It covers the following; Encoders and Decoders, Relays/Contactors, 3 – phase regulated DC power supply unit, passive and active components, Generator switching mechanism and it x-rays the mode of calculation of the basic circuit parameter used in the design.

1.5.  PROJECT REPORT ORGANIZATION

This project report is presented in six chapters to appropriately illustrate the steps involved in its implementation.

Chapter One introduces the project overview, objectives and its significance. Chapter Two is basically the literature review and some theories relevant to the design. Chapter Three x–rays the methodology and analysis while Chapter Four covers the system design and description. Chapter Five elaborates on the implementation, testing and result. Finally, Chapter Six is about the summary of the entire theories and recommendation.