DESIGN, CONSTRUCTION AND INSTALLATION OF A THREE INPUT AUTOMATIC CHANGEOVER SWITCH FROM NATIONAL GRID, SOLAR INVERTER AND STANDBY GENERATOR POWER SUPPLY IN COMPUTER ENGINEERING TECHNOLOGY DEPARTMENT ABIA STATE POLYTECHNIC ABA

This project centers on design, construction and installation of three inputs automatic changeover switch among national grid (EEDC), solar inverter and standby generator power supply. This project work is carried out in the department of computer engineering technology of Abia State Polytechnic Aba. The aim of this project work is to design, construct and install an electrical electronic device that accepts three different input power supplies and and allow only one source of electrical power at a time (Application of 3:1 MUX) in the department of computer engineering technology department in order to have 24 hours power supply. The construction is made up three (3) single phase (120A) contactors, two (2) alternating current (ac) relays (220Vac), two (2) relay base, three (3) phase selector built circuit, three (3) electrical bulbs, three (3) lamp holders, 2.5 feet squared 3/4 ply wood, ten (10) yards of pure copper cable, screw nails. The three contactors are hardwired in such a way that the first contactor serves as master, the second one serve as intermediate and the last contactor serves as a slave. The first ac relay is connected between the first and the second contactor while the second ac relay is connected between the second and the third contactor. When the three different power sources (National Grid, Solar Inverter and Standby Generator) have power supply at the same time, the first ac relay will be energized (N/C) and allowed only the power from the national grid (Master) to pass through the first contactor to the computer engineering technology laboratory. As soon as the national grid lost its power, the same first ac relay is de-energized (N/O) and allowed the power from solar inverter to get the the computer engineering technology laboratory through the second contactor. The third power supply (Generator/Slave) introduces power to the computer engineering technology laboratory through the third ac relay only when the first and second sources of power failed. In order to achieve this, active components such as integrated circuits (Logic gates) and transistor are used. In conclusion, these active components senses when power failed in any of the power sources and sends signals to ac relays to either close or open depending on the state of the relay before power failure.