Thesis Abstract

Abstract
This research project focuses on the design and construction of an automatic change-over switch with an indicator to switch the load from the mains power supply (PHCN) to the power supply from a generator seamlessly. The primary objective is to create a simple and efficient system that allows for automatic switching between the two power sources without manual intervention, providing a reliable power supply to the load. The automatic change-over switch is designed to monitor the availability and quality of the mains power supply continuously. In the event of a power outage or a drop in voltage below a preset threshold, the system will automatically switch the load to the generator power supply. An indicator is incorporated into the design to provide visual feedback on the current power source being utilized. The system utilizes sensors to detect the status of the mains power supply, such as voltage levels and frequency. These sensors are interfaced with a microcontroller unit, which serves as the brain of the system. The microcontroller processes the input from the sensors and controls the switching mechanism to transfer the load between the two power sources. The automatic change-over switch is designed to be user-friendly and reliable, with built-in safety features to prevent power surges or other electrical issues during the switching process. The indicator provides real-time information to the user about the status of the power source, ensuring transparency and ease of monitoring. The construction of the automatic change-over switch involves selecting appropriate components such as relays, sensors, and a microcontroller, as well as designing a suitable circuit layout for seamless operation. Testing and calibration of the system are carried out to ensure its functionality and reliability in real-world scenarios. Overall, this research project aims to provide a practical solution for automatic power source switching in residential, commercial, or industrial settings. By implementing an automatic change-over switch with an indicator, users can enjoy uninterrupted power supply and peace of mind during power outages or fluctuations, enhancing overall system efficiency and reliability.

Thesis Overview

INTRODUCTION

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.
1.1. BACKGROUND OF THE STUDY
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. AIMS AND OBJECTIVES OF THE PROJECT
The aims and objectives of this project is to:
1. Design and construct an automatic change-over switch with indicator that will switch load from the mains power supply (PHCN) power supply (Generator) with simplicity.
2. To introduce a circuitry that will sense power outage and at the same time sense fluctuation in the power supplied to the load at any point time.
1.3. SIGNIFICANCE OF THE PROJECT
This project eliminates the stress, time delay and other drawbacks in manually operated types. The project is modified to display the phase in use at a particular time using a single seven segment Display and its appropriate circuitry.
1.4. SCOPE OF THE STUDY
This project work was carried out primarily with the aim of solving the problem of manual change-over switch when there is need for changing to generator due to power failure from public power supply.
Also, the essence of this project work is to design and construct a 90A, 220V, 50Hz automatic change-over switch which will serve as a standby switch to generator when there is power outage.
1.5. LIMITATIONS OF THE PROJECT
Due to the principal operation of the device, it cannot switch two voltage supply once, during operation. So the power switching of the supplies depends on the state in which the device is, that means it can only be in an on or off state, so as to avoid voltage clashing which will lead to fire outbreak.