DESIGN AND CONSTRUCTION OF UN INTERRUPTIBLE POWER SUPPLY

Abstract

This project · highlights the design and construction of an uninterruptibh~ power supply. This is made possible by the use of high - \ current semiconductor MOSFET switches that convert DC low voltage power to AC line voltage power. An uninterruptible power supply unit thus ensures supply of A.C voltage to an equipment by changing over to an inverted back up DC voltage in the event of a mains failure or other irregularities in the mains supply. During the process ·of the circuit design for the UPS; various factor, such as change over speed, commutation, output waveforms and power quality and efficiency were considered. A just switching relay and power MOSFET are amongst the varous component employed. The pulses obtained fi'om two 555 IC timers, connected in-phase to each other were used for gate firing although a more efficient technique is the sinusoidal pulse width modulation. . The UPS unit was designed to convert a 12V d.c, 30A max supply to feed a 500 watts 240V a.c load at 50ltz.